initial commit

111 files changed, 12680 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
new file mode 100644
index 0000000..bb648ec
--- /dev/null
+++ b/src/Makefile.am
@@ -0,0 +1,120 @@
+lib_LTLIBRARIES = libzs.la
+
+libzs_la_SOURCES = \
+    app_thread.hpp \
+    atomic_bitmap.hpp \
+    atomic_counter.hpp \
+    atomic_ptr.hpp \
+    command.hpp \
+    config.hpp \
+    connecter.hpp \
+    data_distributor.hpp \
+    decoder.hpp \
+    devpoll.hpp \
+    dispatcher.hpp \
+    dummy_aggregator.hpp \
+    dummy_distributor.hpp \
+    encoder.hpp \
+    epoll.hpp \
+    err.hpp \
+    fair_aggregator.hpp \
+    fd.hpp \
+    fd_signaler.hpp \
+    io_object.hpp \
+    io_thread.hpp \
+    ip.hpp \
+    i_api.hpp \
+    i_demux.hpp \
+    i_mux.hpp \
+    i_poller.hpp \
+    i_poll_events.hpp \
+    i_session.hpp \
+    i_signaler.hpp \
+    i_engine.hpp \
+    i_thread.hpp \
+    listener.hpp \
+    kqueue.hpp \
+    load_balancer.hpp \
+    msg.hpp \
+    mutex.hpp \
+    object.hpp \
+    p2p.hpp \
+    pipe.hpp \
+    pipe_reader.hpp \
+    pipe_writer.hpp \
+    platform.hpp \
+    poll.hpp \
+    pub.hpp \
+    rep.hpp \
+    req.hpp \
+    safe_object.hpp \
+    select.hpp \
+    session.hpp \
+    session_stub.hpp \
+    simple_semaphore.hpp \
+    socket_base.hpp \
+    sub.hpp \
+    stdint.hpp \
+    tcp_connecter.hpp \
+    tcp_listener.hpp \
+    tcp_socket.hpp \
+    thread.hpp \
+    uuid.hpp \
+    windows.hpp \
+    wire.hpp \
+    ypipe.hpp \
+    ypollset.hpp \
+    yqueue.hpp \
+    zmq_decoder.hpp \
+    zmq_encoder.hpp \
+    zmq_tcp_engine.hpp \
+    app_thread.cpp \
+    connecter.cpp \
+    data_distributor.cpp \
+    devpoll.hpp \
+    dispatcher.cpp \
+    dummy_aggregator.cpp \
+    dummy_distributor.cpp \
+    epoll.cpp \
+    err.cpp \
+    fair_aggregator.cpp \
+    fd_signaler.cpp \
+    io_object.cpp \
+    io_thread.cpp \
+    ip.cpp \
+    kqueue.cpp \
+    listener.cpp \
+    load_balancer.cpp \
+    object.cpp \
+    p2p.cpp \
+    pipe.cpp \
+    pipe_reader.cpp \
+    pipe_writer.cpp \
+    poll.cpp \
+    pub.cpp \
+    rep.cpp \
+    req.cpp \
+    safe_object.cpp \
+    select.cpp \
+    session.cpp \
+    session_stub.cpp \
+    socket_base.cpp \
+    sub.cpp \
+    tcp_connecter.cpp \
+    tcp_listener.cpp \
+    tcp_socket.cpp \
+    thread.cpp \
+    uuid.cpp \
+    ypollset.cpp \
+    zmq_decoder.cpp \
+    zmq_encoder.cpp \
+    zmq_tcp_engine.cpp \
+    zs.cpp
+
+libzs_la_LDFLAGS = -version-info 0:0:0
+libzs_la_CXXFLAGS = -Wall -pedantic -Werror @ZS_EXTRA_CXXFLAGS@
+
+dist-hook:
+		-rm $(distdir)/src/platform.hpp
+
+
diff --git a/src/app_thread.cpp b/src/app_thread.cpp
new file mode 100644
index 0000000..ca08976
--- /dev/null
+++ b/src/app_thread.cpp
@@ -0,0 +1,221 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#if defined ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#else
+#include <unistd.h>
+#endif
+
+#include "app_thread.hpp"
+#include "dispatcher.hpp"
+#include "err.hpp"
+#include "session.hpp"
+#include "pipe.hpp"
+#include "config.hpp"
+#include "i_api.hpp"
+#include "dummy_aggregator.hpp"
+#include "fair_aggregator.hpp"
+#include "dummy_distributor.hpp"
+#include "data_distributor.hpp"
+#include "load_balancer.hpp"
+#include "p2p.hpp"
+#include "pub.hpp"
+#include "sub.hpp"
+#include "req.hpp"
+#include "rep.hpp"
+
+//  If the RDTSC is available we use it to prevent excessive
+//  polling for commands. The nice thing here is that it will work on any
+//  system with x86 architecture and gcc or MSVC compiler.
+#if (defined __GNUC__ && (defined __i386__ || defined __x86_64__)) ||\
+    (defined _MSC_VER && (defined _M_IX86 || defined _M_X64))
+#define ZS_DELAY_COMMANDS
+#endif
+
+zs::app_thread_t::app_thread_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    object_t (dispatcher_, thread_slot_),
+    tid (0),
+    last_processing_time (0)
+{
+}
+
+void zs::app_thread_t::shutdown ()
+{
+    //  Deallocate all the sessions associated with the thread.
+    while (!sessions.empty ())
+        sessions [0]->shutdown ();
+
+    delete this;
+}
+
+zs::app_thread_t::~app_thread_t ()
+{
+}
+
+void zs::app_thread_t::attach_session (session_t *session_)
+{
+    session_->set_index (sessions.size ());
+    sessions.push_back (session_); 
+}
+
+void zs::app_thread_t::detach_session (session_t *session_)
+{
+    //  O(1) removal of the session from the list.
+    sessions_t::size_type i = session_->get_index ();
+    sessions [i] = sessions [sessions.size () - 1];
+    sessions [i]->set_index (i);
+    sessions.pop_back ();
+}
+
+zs::i_poller *zs::app_thread_t::get_poller ()
+{
+    zs_assert (false);
+}
+
+zs::i_signaler *zs::app_thread_t::get_signaler ()
+{
+    return &pollset;
+}
+
+bool zs::app_thread_t::is_current ()
+{
+    return !sessions.empty () && tid == getpid ();
+}
+
+bool zs::app_thread_t::make_current ()
+{
+    //  If there are object managed by this slot we cannot assign the slot
+    //  to a different thread.
+    if (!sessions.empty ())
+        return false;
+
+    tid = getpid ();
+    return true;
+}
+
+zs::i_api *zs::app_thread_t::create_socket (int type_)
+{
+    i_mux *mux = NULL;
+    i_demux *demux = NULL;
+    session_t *session = NULL;
+    i_api *api = NULL;
+
+    switch (type_) {
+    case ZS_P2P:
+        mux = new dummy_aggregator_t;
+        zs_assert (mux);
+        demux = new dummy_distributor_t;
+        zs_assert (demux);
+        session = new session_t (this, this, mux, demux, true, false);
+        zs_assert (session);
+        api = new p2p_t (this, session);
+        zs_assert (api);
+        break;
+    case ZS_PUB:
+        demux = new data_distributor_t;
+        zs_assert (demux);
+        session = new session_t (this, this, mux, demux, true, false);
+        zs_assert (session);
+        api = new pub_t (this, session);
+        zs_assert (api);
+        break;
+    case ZS_SUB:
+        mux = new fair_aggregator_t;
+        zs_assert (mux);
+        session = new session_t (this, this, mux, demux, true, false);
+        zs_assert (session);
+        api = new sub_t (this, session);
+        zs_assert (api);
+        break;
+    case ZS_REQ:
+        //  TODO
+        zs_assert (false);
+        api = new req_t (this, session);
+        zs_assert (api);
+        break;
+    case ZS_REP:
+        //  TODO
+        zs_assert (false);
+        api = new rep_t (this, session);
+        zs_assert (api);
+        break;
+    default:
+        errno = EINVAL;
+        return NULL;
+    }
+
+    attach_session (session);
+    
+    return api;
+}
+
+void zs::app_thread_t::process_commands (bool block_)
+{
+    ypollset_t::signals_t signals;
+    if (block_)
+        signals = pollset.poll ();
+    else {
+
+#if defined ZS_DELAY_COMMANDS
+        //  Optimised version of command processing - it doesn't have to check
+        //  for incoming commands each time. It does so only if certain time
+        //  elapsed since last command processing. Command delay varies
+        //  depending on CPU speed: It's ~1ms on 3GHz CPU, ~2ms on 1.5GHz CPU
+        //  etc. The optimisation makes sense only on platforms where getting
+        //  a timestamp is a very cheap operation (tens of nanoseconds).
+
+        //  Get timestamp counter.
+#if defined __GNUC__
+        uint32_t low;
+        uint32_t high;
+        __asm__ volatile ("rdtsc" : "=a" (low), "=d" (high));
+        uint64_t current_time = (uint64_t) high << 32 | low;
+#elif defined _MSC_VER
+        uint64_t current_time = __rdtsc ();
+#else
+#error
+#endif
+
+        //  Check whether certain time have elapsed since last command
+        //  processing.
+        if (current_time - last_processing_time <= max_command_delay)
+            return;
+        last_processing_time = current_time;
+#endif
+
+        //  Check whether there are any commands pending for this thread.
+        signals = pollset.check ();
+    }
+
+    if (signals) {
+
+        //  Traverse all the possible sources of commands and process
+        //  all the commands from all of them.
+        for (int i = 0; i != thread_slot_count (); i++) {
+            if (signals & (ypollset_t::signals_t (1) << i)) {
+                command_t cmd;
+                while (dispatcher->read (i, get_thread_slot (), &cmd))
+                    cmd.destination->process_command (cmd);
+            }
+        }
+    }
+}
diff --git a/src/app_thread.hpp b/src/app_thread.hpp
new file mode 100644
index 0000000..61e7ff1
--- /dev/null
+++ b/src/app_thread.hpp
@@ -0,0 +1,95 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_APP_THREAD_HPP_INCLUDED__
+#define __ZS_APP_THREAD_HPP_INCLUDED__
+
+#include <vector>
+
+#include "i_thread.hpp"
+#include "stdint.hpp"
+#include "object.hpp"
+#include "ypollset.hpp"
+
+namespace zs
+{
+
+    class app_thread_t : public object_t, public i_thread
+    {
+    public:
+
+        app_thread_t (class dispatcher_t *dispatcher_, int thread_slot_);
+
+        //  To be called when the whole infrastrucure is being closed (zs_term).
+        void shutdown ();
+
+        //  Returns signaler associated with this application thread.
+        i_signaler *get_signaler ();
+
+        //  Create socket engine in this thread. Return false if the calling
+        //  thread doesn't match the thread handled by this app thread object.
+        struct i_api *create_socket (int type_);
+
+        //  Nota bene: The following two functions are accessed from different
+        //  threads. The caller (dispatcher) is responsible for synchronisation
+        //  of accesses.
+
+        //  Returns true is current thread is associated with the app thread.
+        bool is_current ();
+
+        //  Tries to associate current thread with the app thread object.
+        //  Returns true is successfull, false otherwise.
+        bool make_current ();
+
+        //  Processes commands sent to this thread (if any). If 'block' is
+        //  set to true, returns only after at least one command was processed.
+        void process_commands (bool block_);
+
+        //  i_thread implementation.
+        void attach_session (class session_t *session_);
+        void detach_session (class session_t *session_);
+        struct i_poller *get_poller ();
+
+    private:
+
+        //  Clean-up.
+        ~app_thread_t ();
+
+        //  Thread ID associated with this slot.
+        //  TODO: Virtualise pid_t!
+        //  TODO: Check whether getpid returns unique ID for each thread.
+        int tid;
+
+        //  Vector of all sessionss associated with this app thread.
+        typedef std::vector <class session_t*> sessions_t;
+        sessions_t sessions;
+
+        //  App thread's signaler object.
+        ypollset_t pollset;
+
+        //  Timestamp of when commands were processed the last time.
+        uint64_t last_processing_time;
+
+        app_thread_t (const app_thread_t&);
+        void operator = (const app_thread_t&);
+    };
+
+}
+
+#endif
diff --git a/src/atomic.hpp b/src/atomic.hpp
new file mode 100644
index 0000000..e24b719
--- /dev/null
+++ b/src/atomic.hpp
@@ -0,0 +1,310 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ATOMIC_HPP_INCLUDED__
+#define __ZS_ATOMIC_HPP_INCLUDED__
+
+#include "stdint.hpp"
+
+#if defined ZS_FORCE_MUTEXES
+#define ZS_ATOMIC_MUTEX
+#elif (defined __i386__ || defined __x86_64__) && defined __GNUC__
+#define ZS_ATOMIC_X86
+#elif defined ZMQ_HAVE_WINDOWS
+#define ZS_ATOMIC_WINDOWS
+#elif defined ZMQ_HAVE_SOLARIS
+#define ZS_ATOMIC_SOLARIS
+#else
+#define ZS_ATOMIC_MUTEX
+#endif
+
+namespace zs
+{
+
+    //  Atomic assignement.
+    inline void atomic_uint32_set (volatile uint32_t *p_, uint32_t value_)
+    {
+        *p_ = value_;
+        //  StoreLoad memory barrier should go here on platforms with
+        //  memory models that require it.
+    }
+
+    //  Atomic retrieval of an integer.
+    inline uint32_t atomic_uint32_get (volatile uint32_t *p_)
+    {
+        //  StoreLoad memory barrier should go here on platforms with
+        //  memory models that require it.
+        return *p_;
+    }
+
+    //  Atomic addition. Returns the old value.
+    inline uint32_t atomic_uint32_add (volatile uint32_t *p_, uint32_t delta_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        return InterlockedExchangeAdd ((LONG*) &value, increment_);
+#elif defined ZS_ATOMIC_SOLARIS
+        return atomic_add_32_nv (&value, increment_) - delta_;
+#elif defined ZS_ATOMIC_X86
+        uint32_t old;
+        __asm__ volatile (
+            "lock; xadd %0, %1\n\t"
+            : "=r" (old), "=m" (*p_)
+            : "0" (delta_), "m" (*p_)
+            : "cc", "memory");
+        return old;
+#else
+#error // TODO: 
+        sync.lock ();
+        uint32_t old = *p_;
+        *p_ += delta_;
+        sync.unlock ();
+#endif
+    }
+
+    //  Atomic subtraction. Returns the old value.
+    inline uint32_t atomic_uint32_sub (volatile uint32_t *p_, uint32_t delta_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        LONG delta = - ((LONG) delta_);
+        return InterlockedExchangeAdd ((LONG*) &value, delta);
+#elif defined ZS_ATOMIC_SOLARIS
+        int32_t delta = - ((int32_t) delta_);
+        return atomic_add_32_nv (&value, delta) + delta_;
+#elif defined ZS_ATOMIC_X86
+        uint32_t old = -delta_;
+        __asm__ volatile ("lock; xaddl %0,%1"
+            : "=r" (old), "=m" (*p_)
+            : "0" (old), "m" (*p_)
+            : "cc");
+        return old;
+#else
+#error // TODO: 
+        sync.lock ();
+        uint32_t old = *p_;
+        *p_ -= delta_;
+        sync.unlock ();
+        return old;
+#endif
+    }
+
+    //  Atomic assignement.
+    template <typename T>
+    inline void atomic_ptr_set (volatile T **p_, T *value_)
+    {
+        *p_ = value_;
+        //  StoreLoad memory barrier should go here on platforms with
+        //  memory models that require it.
+    }
+
+    //  Perform atomic 'exchange pointers' operation. Old value is returned.
+    template <typename T>
+    inline void *atomic_ptr_xchg (volatile T **p_, T *value_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        return InterlockedExchangePointer (p_, value_);
+#elif defined ZS_ATOMIC_SOLARIS
+        return atomic_swap_ptr (p_, value_);
+#elif defined ZS_ATOMIC_X86
+        void *old;
+        __asm__ volatile (
+            "lock; xchg %0, %2"
+            : "=r" (old), "=m" (*p_)
+            : "m" (*p_), "0" (value_));
+        return old;
+#else
+#error //  TODO:
+        sync.lock ();
+        void *old = *p_;
+        *p_ = value_;
+        sync.unlock ();
+        return old;
+#endif
+    }
+
+    //  Perform atomic 'compare and swap' operation on the pointer.
+    //  The pointer is compared to 'cmp' argument and if they are
+    //  equal, its value is set to 'value'. Old value of the pointer
+    //  is returned.
+    template <typename T>
+    inline void *atomic_ptr_cas (volatile T **p_, T *cmp_, T *value_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        return InterlockedCompareExchangePointer (p_, value_, cmp_);
+#elif defined ZS_ATOMIC_SOLARIS
+        return atomic_cas_ptr (p_, cmp_, value_);
+#elif defined ZS_ATOMIC_X86
+        void *old;
+        __asm__ volatile (
+            "lock; cmpxchg %2, %3"
+            : "=a" (old), "=m" (*p_)
+            : "r" (value_), "m" (*p_), "0" (cmp_)
+            : "cc");
+        return old;
+#else
+#error //  TODO:
+        sync.lock ();
+        void *old = *p_;
+        if (old == cmp_)
+            *p_ = value_;
+        sync.unlock ();
+        return old;
+#endif
+    }
+
+#if defined ZS_ATOMIC_X86 && defined __x86_64__
+    typedef uint64_t atomic_bitmap_t;
+#else
+    typedef uint32_t atomic_bitmap_t;
+#endif
+
+    //  Atomic assignement.
+    inline void atomic_bitmap_set (volatile atomic_bitmap_t *p_,
+        atomic_bitmap_t value_)
+    {
+        *p_ = value_;
+        //  StoreLoad memory barrier should go here on platforms with
+        //  memory models that require it.
+    }
+
+    //  Bit-test-set-and-reset. Sets one bit of the value and resets
+    //  another one. Returns the original value of the reset bit.
+    inline bool atomic_bitmap_btsr (volatile atomic_bitmap_t *p_,
+        int set_index_, int reset_index_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        while (true) {
+            atomic_bitmap_t oldval = *p_;
+            atomic_bitmap_t newval = (oldval | (atomic_bitmap_t (1) <<
+                set_index_)) & ~(integer_t (1) << reset_index_);
+            if (InterlockedCompareExchange ((volatile LONG*) p_, newval,
+                  oldval) == (LONG) oldval)
+                return (oldval & (atomic_bitmap_t (1) << reset_index_)) ?
+                    true : false; 
+        }
+#elif defined ZS_ATOMIC_SOLARIS
+        while (true) {
+            atomic_bitmap_t oldval = *p_;
+            atomic_bitmap_t newval = (oldval | (atomic_bitmap_t (1) <<
+                set_index_)) & ~(integer_t (1) << reset_index_);
+            if (atomic_cas_32 (p_, oldval, newval) == oldval)
+                return (oldval & (atomic_bitmap_t (1) << reset_index_)) ?
+                    true : false; 
+        }
+#elif defined ZS_ATOMIC_X86
+        atomic_bitmap_t oldval, dummy;
+        __asm__ volatile (
+            "mov %0, %1\n\t"
+            "1:"
+            "mov %1, %2\n\t"
+            "bts %3, %2\n\t"
+            "btr %4, %2\n\t"
+            "lock cmpxchg %2, %0\n\t"
+            "jnz 1b\n\t"
+            : "+m" (*p_), "=&a" (oldval), "=&r" (dummy)
+            : "r" (atomic_bitmap_t (set_index_)),
+                "r" (atomic_bitmap_t (reset_index_))
+            : "cc");
+        return (bool) (oldval & (atomic_bitmap_t (1) << reset_index_)); 
+#else
+#error // TODO:
+        sync.lock ();
+        atomic_bitmap_t oldval = *p_;
+        *p_ = (oldval | (atomic_bitmap_t (1) << set_index_)) &
+            ~(atomic_bitmap_t (1) << reset_index_);
+        sync.unlock ();
+        return (oldval & (atomic_bitmap_t (1) << reset_index_)) ? true : false;
+#endif
+    }
+
+    //  Sets value to newval. Returns the original value.
+    inline atomic_bitmap_t atomic_bitmap_xchg (volatile atomic_bitmap_t *p_,
+        atomic_bitmap_t newval_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        return InterlockedExchange ((volatile LONG*) p_, newval_);
+#elif defined ZS_ATOMIC_SOLARIS
+        return atomic_swap_32 (p_, newval_);
+#elif defined ZS_ATOMIC_X86
+        atomic_bitmap_t oldval = newval_;
+        __asm__ volatile (
+            "lock; xchg %0, %1"
+            : "=r" (oldval)
+            : "m" (*p_), "0" (oldval)
+            : "memory");
+        return oldval; 
+#else
+#error //  TODO:
+        sync.lock ();
+        atomic_bitmap_t oldval = *p_;
+        *p_ = newval_;
+        sync.unlock ();
+#endif
+    }
+
+    //  izte is "if-zero-then-else" atomic operation - if the value is zero
+    //  it substitutes it by 'thenval' else it rewrites it by 'elseval'.
+    //  Original value of the integer is returned from this function.
+    inline atomic_bitmap_t atomic_bitmap_izte (volatile atomic_bitmap_t *p_,
+            atomic_bitmap_t thenval_,  atomic_bitmap_t elseval_)
+    {
+#if defined ZS_ATOMIC_WINDOWS
+        while (true) {
+            atomic_bitmap_t oldval = *p_;
+            atomic_bitmap_t newval = (oldval ? elseval_ : thenval_); 
+            if (InterlockedCompareExchange ((volatile LONG*) p_, newval,
+                  oldval) == (LONG) oldval)
+                return oldval;
+        }
+#elif defined ZS_ATOMIC_SOLARIS
+        while (true) {
+            atomic_bitmap_t oldval = *p_;
+            atomic_bitmap_t newval = (oldval ? elseval_ : thenval_); 
+            if (atomic_cas_32 (p_, oldval, newval) == oldval)
+                return oldval;
+        }
+#elif defined ZS_ATOMIC_X86
+        atomic_bitmap_t oldval;
+        atomic_bitmap_t dummy;
+        __asm__ volatile (
+            "mov %0, %1\n\t"
+            "1:"
+            "mov %3, %2\n\t"
+            "test %1, %1\n\t"
+            "jz 2f\n\t"
+            "mov %4, %2\n\t"
+            "2:"
+            "lock cmpxchg %2, %0\n\t"
+            "jnz 1b\n\t"
+            : "+m" (*p_), "=&a" (oldval), "=&r" (dummy)
+            : "r" (thenval_), "r" (elseval_)
+            : "cc");
+        return oldval;
+#else
+#error //  TODO:
+        sync.lock ();
+        atomic_bitmap_t oldval = *p_;
+        *p_ = oldval ? elseval_ : thenval_;
+        sync.unlock ();
+        return oldval;
+#endif
+    }
+
+}
+
+#endif
diff --git a/src/atomic_bitmap.hpp b/src/atomic_bitmap.hpp
new file mode 100644
index 0000000..a5440de
--- /dev/null
+++ b/src/atomic_bitmap.hpp
@@ -0,0 +1,286 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ATOMIC_BITMAP_HPP_INCLUDED__
+#define __ZS_ATOMIC_BITMAP_HPP_INCLUDED__
+
+#include "stdint.hpp"
+#include "platform.hpp"
+
+//  These are the conditions to choose between different implementations
+//  of atomic_bitmap.
+
+#if defined ZS_FORCE_MUTEXES
+#define ZS_ATOMIC_BITMAP_MUTEX
+#elif (defined __i386__ || defined __x86_64__) && defined __GNUC__
+#define ZS_ATOMIC_BITMAP_X86
+#elif 0 && defined __sparc__ && defined __GNUC__
+#define ZS_ATOMIC_BITMAP_SPARC
+#elif defined ZS_HAVE_WINDOWS
+#define ZS_ATOMIC_BITMAP_WINDOWS
+#elif defined ZS_HAVE_SOLARIS
+#define ZS_ATOMIC_BITMAP_SOLARIS
+#else
+#define ZS_ATOMIC_BITMAP_MUTEX
+#endif
+
+#if defined ZS_ATOMIC_BITMAP_MUTEX
+#include "mutex.hpp"
+#elif defined ZS_ATOMIC_BITMAP_WINDOWS
+#include "windows.hpp"
+#elif defined ZS_ATOMIC_BITMAP_SOLARIS
+#include <atomic.h>
+#endif
+
+namespace zs
+{
+
+    //  This class encapuslates several bitwise atomic operations on unsigned
+    //  integer. Selection of operations is driven specifically by the needs
+    //  of ypollset implementation.
+
+    class atomic_bitmap_t
+    {
+    public:
+
+#if (defined ZMQ_ATOMIC_BITMAP_X86 || defined ZMQ_FORCE_MUTEXES) \
+    && defined __x86_64__
+        typedef uint64_t bitmap_t;
+#else
+        typedef uint32_t bitmap_t;
+#endif
+
+        inline atomic_bitmap_t (bitmap_t value_ = 0) :
+            value (value_)
+        {
+        }
+
+        inline ~atomic_bitmap_t ()
+        {
+        }
+
+        //  Bit-test-set-and-reset. Sets one bit of the value and resets
+        //  another one. Returns the original value of the reset bit.
+        inline bool btsr (int set_index_, int reset_index_)
+        {
+#if defined ZS_ATOMIC_BITMAP_WINDOWS
+            while (true) {
+                bitmap_t oldval = value;
+                bitmap_t newval = (oldval | (bitmap_t (1) << set_index_)) &
+                    ~(bitmap_t (1) << reset_index_);
+                if (InterlockedCompareExchange ((volatile LONG*) &value, newval,
+                      oldval) == (LONG) oldval)
+                    return (oldval & (bitmap_t (1) << reset_index_)) ?
+                        true : false;
+            }
+#elif defined ZS_ATOMIC_BITMAP_SOLARIS
+            while (true) {
+                bitmap_t oldval = value;
+                bitmap_t newval = (oldval | (bitmap_t (1) << set_index_)) &
+                    ~(bitmap_t (1) << reset_index_);
+                if (atomic_cas_32 (&value, oldval, newval) == oldval)
+                    return (oldval & (bitmap_t (1) << reset_index_)) ?
+                        true : false;
+            }
+#elif defined ZS_ATOMIC_BITMAP_X86
+            bitmap_t oldval, dummy;
+            __asm__ volatile (
+                "mov %0, %1\n\t"
+                "1:"
+                "mov %1, %2\n\t"
+                "bts %3, %2\n\t"
+                "btr %4, %2\n\t"
+                "lock cmpxchg %2, %0\n\t"
+                "jnz 1b\n\t"
+                : "+m" (value), "=&a" (oldval), "=&r" (dummy)
+                : "r" (bitmap_t(set_index_)), "r" (bitmap_t(reset_index_))
+                : "cc");
+            return (bool) (oldval & (bitmap_t(1) << reset_index_));
+#elif defined ZS_ATOMIC_BITMAP_SPARC
+            volatile bitmap_t* valptr = &value;
+            bitmap_t set_val = bitmap_t(1) << set_index_;
+            bitmap_t reset_val = ~(bitmap_t(1) << reset_index_);
+            bitmap_t tmp;
+            bitmap_t oldval;
+            __asm__ volatile(
+                "ld       [%5], %2       \n\t"
+                "1:                      \n\t"
+                "or       %2, %0, %3     \n\t"
+                "and      %3, %1, %3     \n\t"
+                "cas      [%5], %2, %3   \n\t"
+                "cmp      %2, %3         \n\t"
+                "bne,a,pn %%icc, 1b      \n\t"
+                "mov      %3, %2         \n\t"
+                : "+r" (set_val), "+r" (reset_val), "=&r" (tmp),
+                  "=&r" (oldval), "+m" (*valptr)
+                : "r" (valptr)
+                : "cc");
+            return oldval;
+#elif defined ZS_ATOMIC_BITMAP_MUTEX
+            sync.lock ();
+            bitmap_t oldval = value;
+            value = (oldval | (bitmap_t (1) << set_index_)) &
+                ~(bitmap_t (1) << reset_index_);
+            sync.unlock ();
+            return (oldval & (bitmap_t (1) << reset_index_)) ? true : false;
+#else
+#error
+#endif
+        }
+
+        //  Sets value to newval. Returns the original value.
+        inline bitmap_t xchg (bitmap_t newval_)
+        {
+            bitmap_t oldval;
+#if defined ZS_ATOMIC_BITMAP_WINDOWS
+            oldval = InterlockedExchange ((volatile LONG*) &value, newval_);
+#elif defined ZS_ATOMIC_BITMAP_SOLARIS
+            oldval = atomic_swap_32 (&value, newval_);
+#elif defined ZS_ATOMIC_BITMAP_X86
+            oldval = newval_;
+            __asm__ volatile (
+                "lock; xchg %0, %1"
+                : "=r" (oldval)
+                : "m" (value), "0" (oldval)
+                : "memory");
+#elif defined ZS_ATOMIC_BITMAP_SPARC
+            oldval = value;
+            volatile bitmap_t* ptrin = &value;
+            bitmap_t tmp;
+            bitmap_t prev;
+            __asm__ __volatile__(
+                "ld [%4], %1\n\t"
+                "1:\n\t"
+                "mov %0, %2\n\t"
+                "cas [%4], %1, %2\n\t"
+                "cmp %1, %2\n\t"
+                "bne,a,pn %%icc, 1b\n\t"
+                "mov %2, %1\n\t"
+                : "+r" (newval_), "=&r" (tmp), "=&r" (prev), "+m" (*ptrin)
+                : "r" (ptrin)
+                : "cc");
+            return prev;
+#elif defined ZS_ATOMIC_BITMAP_MUTEX
+            sync.lock ();
+            oldval = value;
+            value = newval_;
+            sync.unlock ();
+#else
+#error
+#endif
+            return oldval;
+        }
+
+        //  izte is "if-zero-then-else" atomic operation - if the value is zero
+        //  it substitutes it by 'thenval' else it rewrites it by 'elseval'.
+        //  Original value of the integer is returned from this function.
+        inline bitmap_t izte (bitmap_t thenval_,
+            bitmap_t elseval_)
+        {
+#if defined ZS_ATOMIC_BITMAP_WINDOWS
+            while (true) {
+                bitmap_t oldval = value;
+                bitmap_t newval = oldval == 0 ? thenval_ : elseval_;
+                if (InterlockedCompareExchange ((volatile LONG*) &value,
+                      newval, oldval) == (LONG) oldval)
+                    return oldval;
+            }
+#elif defined ZS_ATOMIC_BITMAP_SOLARIS
+            while (true) {
+                bitmap_t oldval = value;
+                bitmap_t newval = oldval == 0 ? thenval_ : elseval_;
+                if (atomic_cas_32 (&value, oldval, newval) == oldval)
+                    return oldval;
+            }
+#elif defined ZS_ATOMIC_BITMAP_X86
+            bitmap_t oldval;
+            bitmap_t dummy;
+            __asm__ volatile (
+                "mov %0, %1\n\t"
+                "1:"
+                "mov %3, %2\n\t"
+                "test %1, %1\n\t"
+                "jz 2f\n\t"
+                "mov %4, %2\n\t"
+                "2:"
+                "lock cmpxchg %2, %0\n\t"
+                "jnz 1b\n\t"
+                : "+m" (value), "=&a" (oldval), "=&r" (dummy)
+                : "r" (thenval_), "r" (elseval_)
+                : "cc");
+            return oldval;
+#elif defined ZS_ATOMIC_BITMAP_SPARC
+            volatile bitmap_t* ptrin = &value;
+            bitmap_t tmp;
+            bitmap_t prev;
+            __asm__ __volatile__(
+                "ld      [%3], %0       \n\t"
+                "mov     0,    %1       \n\t"
+                "cas     [%3], %1, %4   \n\t"
+                "cmp     %0,   %1       \n\t"
+                "be,a,pn %%icc,1f       \n\t"
+                "ld      [%3], %0       \n\t"
+                "cas     [%3], %0, %5   \n\t"
+                "1:                     \n\t"
+                : "=&r" (tmp), "=&r" (prev), "+m" (*ptrin)
+                : "r" (ptrin), "r" (thenval_), "r" (elseval_)
+                : "cc");
+            return prev;
+#elif defined ZS_ATOMIC_BITMAP_MUTEX
+            sync.lock ();
+            bitmap_t oldval = value;
+            value = oldval ? elseval_ : thenval_;
+            sync.unlock ();
+            return oldval;
+#else
+#error
+#endif
+        }
+
+    private:
+
+        volatile bitmap_t value;
+#if defined ZS_ATOMIC_BITMAP_MUTEX
+        mutex_t sync;
+#endif
+
+        atomic_bitmap_t (const atomic_bitmap_t&);
+        void operator = (const atomic_bitmap_t&);
+    };
+
+}
+
+//  Remove macros local to this file.
+#if defined ZS_ATOMIC_BITMAP_WINDOWS
+#undef ZS_ATOMIC_BITMAP_WINDOWS
+#endif
+#if defined ZS_ATOMIC_BITMAP_SOLARIS
+#undef ZS_ATOMIC_BITMAP_SOLARIS
+#endif
+#if defined ZS_ATOMIC_BITMAP_X86
+#undef ZS_ATOMIC_BITMAP_X86
+#endif
+#if defined ZS_ATOMIC_BITMAP_SPARC
+#undef ZS_ATOMIC_BITMAP_SPARC
+#endif
+#if defined ZS_ATOMIC_BITMAP_MUTEX
+#undef ZS_ATOMIC_BITMAP_MUTEX
+#endif
+
+#endif
diff --git a/src/atomic_counter.hpp b/src/atomic_counter.hpp
new file mode 100644
index 0000000..0873fdd
--- /dev/null
+++ b/src/atomic_counter.hpp
@@ -0,0 +1,197 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef __ZS_ATOMIC_COUNTER_HPP_INCLUDED__
+#define __ZS_ATOMIC_COUNTER_HPP_INCLUDED__
+
+#include "stdint.hpp"
+#include "platform.hpp"
+
+#if defined ZS_FORCE_MUTEXES
+#define ZS_ATOMIC_COUNTER_MUTEX
+#elif (defined __i386__ || defined __x86_64__) && defined __GNUC__
+#define ZS_ATOMIC_COUNTER_X86
+#elif 0 && defined __sparc__ && defined __GNUC__
+#define ZS_ATOMIC_COUNTER_SPARC
+#elif defined ZS_HAVE_WINDOWS
+#define ZS_ATOMIC_COUNTER_WINDOWS
+#elif defined ZS_HAVE_SOLARIS
+#define ZS_ATOMIC_COUNTER_SOLARIS
+#else
+#define ZS_ATOMIC_COUNTER_MUTEX
+#endif
+
+#if defined ZS_ATOMIC_COUNTER_MUTEX
+#include "mutex.hpp"
+#elif defined ZS_ATOMIC_COUNTER_WINDOWS
+#include "windows.hpp"
+#elif defined ZS_ATOMIC_COUNTER_SOLARIS
+#include <atomic.h>
+#endif
+
+namespace zs
+{
+
+    //  This class represents an integer that can be incremented/decremented
+    //  in atomic fashion.
+
+    class atomic_counter_t
+    {
+    public:
+
+        typedef uint32_t integer_t;
+
+        inline atomic_counter_t (integer_t value_ = 0) :
+            value (value_)
+        {
+        }
+
+        inline ~atomic_counter_t ()
+        {
+        }
+
+        //  Set counter value (not thread-safe).
+        inline void set (integer_t value_)
+        {
+            value = value_;
+        }
+
+        //  Atomic addition. Returns the old value.
+        inline integer_t add (integer_t increment_)
+        {
+            integer_t old_value;
+
+#if defined ZS_ATOMIC_COUNTER_WINDOWS
+            old_value = InterlockedExchangeAdd ((LONG*) &value, increment_);
+#elif defined ZS_ATOMIC_COUNTER_SOLARIS
+            integer_t new_value = atomic_add_32_nv (&value, increment_);
+            old_value = new_value - increment_;
+#elif defined ZS_ATOMIC_COUNTER_X86
+            __asm__ volatile (
+                "lock; xadd %0, %1          \n\t"
+                : "=r" (old_value), "=m" (value)
+                : "0" (increment_), "m" (value)
+                : "cc", "memory");
+#elif defined ZS_ATOMIC_COUNTER_SPARC
+            integer_t tmp;
+            __asm__ volatile (
+                "ld [%4], %0                \n\t"
+                "1:                         \n\t"
+                "add %0, %3, %1             \n\t"
+                "cas [%4], %0, %1           \n\t"
+                "cmp %0, %1                 \n\t"
+                "bne,a,pn %%icc, 1b         \n\t"
+                "mov %1, %0                 \n\t"
+                : "=&r" (old_value), "=&r" (tmp), "=m" (value)
+                : "r" (increment_), "r" (&value)
+                : "cc", "memory");
+#elif defined ZS_ATOMIC_COUNTER_MUTEX
+            sync.lock ();
+            old_value = value;
+            value += increment_;
+            sync.unlock ();
+#else
+#error
+#endif
+            return old_value;
+        }
+
+        //  Atomic subtraction. Returns false if the counter drops to zero.
+        inline bool sub (integer_t decrement)
+        {
+#if defined ZS_ATOMIC_COUNTER_WINDOWS
+            LONG delta = - ((LONG) decrement);
+            integer_t old = InterlockedExchangeAdd ((LONG*) &value, delta);
+            return old - decrement != 0;
+#elif defined ZS_ATOMIC_COUNTER_SOLARIS
+            int32_t delta = - ((int32_t) decrement);
+            integer_t nv = atomic_add_32_nv (&value, delta);
+            return nv != 0;
+#elif defined ZS_ATOMIC_COUNTER_X86
+            integer_t oldval = -decrement;
+            volatile integer_t *val = &value;
+            __asm__ volatile ("lock; xaddl %0,%1"
+                : "=r" (oldval), "=m" (*val)
+                : "0" (oldval), "m" (*val)
+                : "cc");
+            return oldval != decrement;
+#elif defined ZS_ATOMIC_COUNTER_SPARC
+            volatile integer_t *val = &value;
+            integer_t tmp;
+            integer_t result;
+            __asm__ volatile(
+                "ld [%4], %1\n\t"
+                "1:\n\t"
+                "add %1, %0, %2\n\t"
+                "cas [%4], %1, %2\n\t"
+                "cmp %1, %2\n\t"
+                "bne,a,pn %%icc, 1b\n\t"
+                "mov %2, %1\n\t"
+                : "+r" (-decrement), "=&r" (tmp), "=&r" (result), "+m" (*val)
+                : "r" (val)
+                : "cc");
+            return result <= decrement;
+#elif defined ZS_ATOMIC_COUNTER_MUTEX
+            sync.lock ();
+            value -= decrement;
+            bool result = value ? true : false;
+            sync.unlock ();
+            return result;
+#else
+#error
+#endif
+        }
+
+        inline integer_t get ()
+        {
+            return value;
+        }
+
+    private:
+
+        volatile integer_t value;
+#if defined ZS_ATOMIC_COUNTER_MUTEX
+        mutex_t sync;
+#endif
+
+        atomic_counter_t (const atomic_counter_t&);
+        void operator = (const atomic_counter_t&);
+    };
+
+}
+
+//  Remove macros local to this file.
+#if defined ZS_ATOMIC_COUNTER_WINDOWS
+#undef ZS_ATOMIC_COUNTER_WINDOWS
+#endif
+#if defined ZS_ATOMIC_COUNTER_SOLARIS
+#undef ZS_ATOMIC_COUNTER_SOLARIS
+#endif
+#if defined ZS_ATOMIC_COUNTER_X86
+#undef ZS_ATOMIC_COUNTER_X86
+#endif
+#if defined ZS_ATOMIC_COUNTER_SPARC
+#undef ZS_ATOMIC_COUNTER_SPARC
+#endif
+#if defined ZS_ATOMIC_COUNTER_MUTEX
+#undef ZS_ATOMIC_COUNTER_MUTEX
+#endif
+
+#endif
diff --git a/src/atomic_ptr.hpp b/src/atomic_ptr.hpp
new file mode 100644
index 0000000..fcc4e73
--- /dev/null
+++ b/src/atomic_ptr.hpp
@@ -0,0 +1,189 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef __ZS_ATOMIC_PTR_HPP_INCLUDED__
+#define __ZS_ATOMIC_PTR_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#if defined ZS_FORCE_MUTEXES
+#define ZS_ATOMIC_PTR_MUTEX
+#elif (defined __i386__ || defined __x86_64__) && defined __GNUC__
+#define ZS_ATOMIC_PTR_X86
+#elif 0 && defined __sparc__ && defined __GNUC__
+#define ZS_ATOMIC_PTR_SPARC
+#elif defined ZS_HAVE_WINDOWS
+#define ZS_ATOMIC_PTR_WINDOWS
+#elif defined ZS_HAVE_SOLARIS
+#define ZS_ATOMIC_PTR_SOLARIS
+#else
+#define ZS_ATOMIC_PTR_MUTEX
+#endif
+
+#if defined ZS_ATOMIC_PTR_MUTEX
+#include "mutex.hpp"
+#elif defined ZS_ATOMIC_PTR_WINDOWS
+#include "windows.hpp"
+#elif defined ZS_ATOMIC_PTR_SOLARIS
+#include <atomic.h>
+#endif
+
+namespace zs
+{
+
+    //  This class encapsulates several atomic operations on pointers.
+
+    template <typename T> class atomic_ptr_t
+    {
+    public:
+
+        //  Initialise atomic pointer
+        inline atomic_ptr_t ()
+        {
+            ptr = NULL;
+        }
+
+        //  Destroy atomic pointer
+        inline ~atomic_ptr_t ()
+        {
+        }
+
+        //  Set value of atomic pointer in a non-threadsafe way
+        //  Use this function only when you are sure that at most one
+        //  thread is accessing the pointer at the moment.
+        inline void set (T *ptr_)
+        {
+            this->ptr = ptr_;
+        }
+
+        //  Perform atomic 'exchange pointers' operation. Pointer is set
+        //  to the 'val' value. Old value is returned.
+        inline T *xchg (T *val_)
+        {
+#if defined ZS_ATOMIC_PTR_WINDOWS
+            return (T*) InterlockedExchangePointer (&ptr, val_);
+#elif defined ZS_ATOMIC_PTR_SOLARIS
+            return (T*) atomic_swap_ptr (&ptr, val_);
+#elif defined ZS_ATOMIC_PTR_X86
+            T *old;
+            __asm__ volatile (
+                "lock; xchg %0, %2"
+                : "=r" (old), "=m" (ptr)
+                : "m" (ptr), "0" (val_));
+            return old;
+#elif defined ZS_ATOMIC_PTR_SPARC
+            T* newptr = val_;
+            volatile T** ptrin = &ptr;
+            T* tmp;
+            T* prev;
+            __asm__ __volatile__(
+                "ld [%4], %1\n\t"
+                "1:\n\t"
+                "mov %0, %2\n\t"
+                "cas [%4], %1, %2\n\t"
+                "cmp %1, %2\n\t"
+                "bne,a,pn %%icc, 1b\n\t"
+                "mov %2, %1\n\t"
+                : "+r" (newptr), "=&r" (tmp), "=&r" (prev), "+m" (*ptrin)
+                : "r" (ptrin)
+                : "cc");
+            return prev;
+#elif defined ZS_ATOMIC_PTR_MUTEX
+            sync.lock ();
+            T *old = (T*) ptr;
+            ptr = val_;
+            sync.unlock ();
+            return old;
+#else
+#error
+#endif
+        }
+
+        //  Perform atomic 'compare and swap' operation on the pointer.
+        //  The pointer is compared to 'cmp' argument and if they are
+        //  equal, its value is set to 'val'. Old value of the pointer
+        //  is returned.
+        inline T *cas (T *cmp_, T *val_)
+        {
+#if defined ZS_ATOMIC_PTR_WINDOWS
+            return (T*) InterlockedCompareExchangePointer (
+                (volatile PVOID*) &ptr, val_, cmp_);
+#elif defined ZS_ATOMIC_PTR_SOLARIS
+            return (T*) atomic_cas_ptr (&ptr, cmp_, val_);
+#elif defined ZS_ATOMIC_PTR_X86
+            T *old;
+            __asm__ volatile (
+                "lock; cmpxchg %2, %3"
+                : "=a" (old), "=m" (ptr)
+                : "r" (val_), "m" (ptr), "0" (cmp_)
+                : "cc");
+            return old;
+#elif defined ZS_ATOMIC_PTR_SPARC
+            volatile T** ptrin = &ptr;
+            volatile T* prev = ptr;
+            __asm__ __volatile__(
+                "cas [%3], %1, %2\n\t"
+                : "+m" (*ptrin)
+                : "r" (cmp_), "r" (val_), "r" (ptrin)
+                : "cc");
+            return prev;
+#elif defined ZS_ATOMIC_PTR_MUTEX
+            sync.lock ();
+            T *old = (T*) ptr;
+            if (ptr == cmp_)
+                ptr = val_;
+            sync.unlock ();
+            return old;
+#else
+#error
+#endif
+        }
+
+    private:
+
+        volatile T *ptr;
+#if defined ZS_ATOMIC_PTR_MUTEX
+        mutex_t sync;
+#endif
+
+        atomic_ptr_t (const atomic_ptr_t&);
+        void operator = (const atomic_ptr_t&);
+    };
+
+}
+
+//  Remove macros local to this file.
+#if defined ZS_ATOMIC_PTR_WINDOWS
+#undef ZS_ATOMIC_PTR_WINDOWS
+#endif
+#if defined ZS_ATOMIC_PTR_SOLARIS
+#undef ZS_ATOMIC_PTR_SOLARIS
+#endif
+#if defined ZS_ATOMIC_PTR_X86
+#undef ZS_ATOMIC_PTR_X86
+#endif
+#if defined ZS_ATOMIC_PTR_SPARC
+#undef ZS_ATOMIC_PTR_SPARC
+#endif
+#if defined ZS_ATOMIC_PTR_MUTEX
+#undef ZS_ATOMIC_PTR_MUTEX
+#endif
+
+#endif
diff --git a/src/command.hpp b/src/command.hpp
new file mode 100644
index 0000000..0553137
--- /dev/null
+++ b/src/command.hpp
@@ -0,0 +1,98 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_COMMAND_HPP_INCLUDED__
+#define __ZS_COMMAND_HPP_INCLUDED__
+
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    //  This structure defines the commands that can be sent between threads.
+
+    struct command_t
+    {
+        //  Object to process the command.
+        class object_t *destination;
+
+        enum type_t
+        {
+            stop,
+            bind,
+            head,
+            tail,
+            reg,
+            reg_and_bind,
+            unreg,
+            engine,
+            terminate,
+            terminate_ack
+        } type;
+
+        union {
+
+            struct {
+            } stop;
+
+            struct {
+                class pipe_reader_t *reader;
+                class session_t *peer;
+            } bind;
+
+            struct {
+                uint64_t bytes;
+            } tail;
+
+            struct {
+                uint64_t bytes;
+            } head;
+
+            struct {
+                class simple_semaphore_t *smph;
+            } reg;
+
+            struct {
+                class session_t *peer;
+                bool flow_in;
+                bool flow_out;
+            } reg_and_bind;
+
+            struct {
+                class simple_semaphore_t *smph;
+            } unreg;
+
+            //  TODO: Engine object won't be deallocated on terminal shutdown
+            //  while the command is still on the fly!
+            struct {
+                class i_engine *engine;
+            } engine;
+
+            struct {
+            } terminate;
+
+            struct {
+            } terminate_ack;
+
+        } args;
+    };
+
+}    
+
+#endif
diff --git a/src/config.hpp b/src/config.hpp
new file mode 100644
index 0000000..a0569ea
--- /dev/null
+++ b/src/config.hpp
@@ -0,0 +1,71 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_CONFIG_HPP_INCLUDED__
+#define __ZS_CONFIG_HPP_INCLUDED__
+
+namespace zs
+{
+
+    //  Compile-time settings.
+
+    enum 
+    {
+
+        //  Number of new messages in message pipe needed to trigger new memory
+        //  allocation. Setting this parameter to 256 decreases the impact of
+        //  memory allocation by approximately 99.6%
+        message_pipe_granularity = 256,
+
+        //  Number of new commands in command pipe needed to trigger new memory
+        //  allocation. The number should  be kept low to decrease the memory
+        //  footprint of dispatcher.
+        command_pipe_granularity = 4,
+
+        //  Maximal batching size for engines with receiving functionality.
+        //  So, if there are 10 messages that fit into the batch size, all of
+        //  them may be read by a single 'recv' system call, thus avoiding
+        //  unnecessary network stack traversals.
+        in_batch_size = 8192,
+
+        //  Maximal batching size for engines with sending functionality.
+        //  So, if there are 10 messages that fit into the batch size, all of
+        //  them may be written by a single 'send' system call, thus avoiding
+        //  unnecessary network stack traversals.
+        out_batch_size = 8192,        
+
+        //  Maximum number of events the I/O thread can process in one go.
+        max_io_events = 256,
+
+        //  Maximal wait time for a timer (milliseconds).
+        max_timer_period = 100,
+
+        //  Maximal delay to process command in API thread (in CPU ticks).
+        //  3,000,000 ticks equals to 1 - 2 milliseconds on current CPUs.
+        max_command_delay = 3000000,
+
+        //  Maximal number of non-accepted connections that can be held by
+        //  TCP listener object.
+        tcp_connection_backlog = 10
+
+    };
+
+}
+
+#endif
diff --git a/src/connecter.cpp b/src/connecter.cpp
new file mode 100644
index 0000000..a21dde3
--- /dev/null
+++ b/src/connecter.cpp
@@ -0,0 +1,189 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "connecter.hpp"
+#include "io_thread.hpp"
+#include "session.hpp"
+#include "err.hpp"
+#include "simple_semaphore.hpp"
+#include "zmq_tcp_engine.hpp"
+
+zs::connecter_t::connecter_t (io_thread_t *thread_, const char *addr_,
+      session_t *session_) :
+    io_object_t (thread_),
+    state (idle),
+    poller (NULL),
+    session (session_),
+    addr (addr_),
+    identity ("abcde"),
+    engine (NULL)
+{
+}
+
+void zs::connecter_t::terminate ()
+{
+    delete this;
+}
+
+void zs::connecter_t::shutdown ()
+{
+    delete this;
+}
+
+zs::connecter_t::~connecter_t ()
+{
+}
+
+void zs::connecter_t::process_reg (simple_semaphore_t *smph_)
+{
+    //  Fet poller pointer for further use.
+    zs_assert (!poller);
+    poller = get_poller ();
+
+    //  Ask the session to register itself with the I/O thread. Note that
+    //  the session is living in the same I/O thread, thus this results
+    //  in a synchronous call.
+    session->inc_seqnum ();
+    send_reg (session, NULL);
+
+    //  Unlock the application thread that created the connecter.
+    if (smph_)
+        smph_->post ();
+
+    //  Manually trigger timer event which will launch asynchronous connect.
+    state = waiting;
+    timer_event ();
+}
+
+void zs::connecter_t::process_unreg (simple_semaphore_t *smph_)
+{
+    //  Unregister connecter/engine from the poller.
+    zs_assert (poller);
+    if (state == connecting)
+        poller->rm_fd (handle);
+    else if (state == waiting)
+        poller->cancel_timer (this);
+    else if (state == sending)
+        engine->terminate ();
+
+    //  Unlock the application thread closing the connecter.
+    if (smph_)
+        smph_->post ();
+}
+
+void zs::connecter_t::in_event ()
+{
+    //  Error occured in asynchronous connect. Retry to connect after a while.
+    if (state == connecting) {
+        fd_t fd = tcp_connecter.connect ();
+        zs_assert (fd == retired_fd);
+        poller->rm_fd (handle);
+        poller->add_timer (this);
+        state = waiting;
+        return;
+    }
+
+    zs_assert (false);
+}
+
+void zs::connecter_t::out_event ()
+{
+    if (state == connecting) {
+
+        fd_t fd = tcp_connecter.connect ();
+        if (fd == retired_fd) {
+            poller->rm_fd (handle);
+            poller->add_timer (this);
+            state = waiting;
+            return;
+        }
+
+        poller->rm_fd (handle);
+        engine = new zmq_tcp_engine_t (fd);
+        zs_assert (engine);
+        engine->attach (poller, this);
+        state = sending;
+        return;
+    }
+
+    zs_assert (false);
+}
+
+void zs::connecter_t::timer_event ()
+{
+    zs_assert (state == waiting);
+
+    //  Initiate async connect and start polling for its completion. If async
+    //  connect fails instantly, try to reconnect after a while.
+    int rc = tcp_connecter.open (addr.c_str ());
+    if (rc == 0) {
+        state = connecting;
+        in_event ();
+    }
+    else if (rc == 1) {
+        handle = poller->add_fd (tcp_connecter.get_fd (), this);
+        poller->set_pollout (handle);
+        state = connecting;
+    }
+    else {
+        poller->add_timer (this);
+        state = waiting;
+    }
+}
+
+void zs::connecter_t::set_engine (struct i_engine *engine_)
+{
+    engine = engine_;
+}
+
+bool zs::connecter_t::read (zs_msg *msg_)
+{
+    zs_assert (state == sending);
+
+    //  Deallocate old content of the message just in case.
+    zs_msg_close (msg_);
+
+    //  Send the identity.
+    zs_msg_init_size (msg_, identity.size ());
+    memcpy (zs_msg_data (msg_), identity.c_str (), identity.size ());
+
+    //  Ask engine to unregister from the poller.
+    i_engine *e = engine;
+    engine->detach ();
+
+    //  Attach the engine to the session. (Note that this is actually
+    //  a synchronous call.
+    session->inc_seqnum ();
+    send_engine (session, e);
+
+    state = idle;
+
+    return true;    
+}
+
+bool zs::connecter_t::write (struct zs_msg *msg_)
+{
+    //  No incoming messages are accepted till identity is sent.
+    return false;
+}
+
+void zs::connecter_t::flush ()
+{
+    //  No incoming messages are accepted till identity is sent.
+}
diff --git a/src/connecter.hpp b/src/connecter.hpp
new file mode 100644
index 0000000..91dbf17
--- /dev/null
+++ b/src/connecter.hpp
@@ -0,0 +1,99 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_CONNECTER_HPP_INCLUDED__
+#define __ZS_CONNECTER_HPP_INCLUDED__
+
+#include <string>
+
+#include "../include/zs.h"
+
+#include "i_poller.hpp"
+#include "io_object.hpp"
+#include "i_poll_events.hpp"
+#include "i_session.hpp"
+#include "tcp_connecter.hpp"
+
+namespace zs
+{
+
+    class connecter_t : public io_object_t, public i_poll_events,
+        public i_session
+    {
+    public:
+
+        connecter_t (class io_thread_t *thread_, const char *addr_,
+            class session_t *session_);
+
+        void terminate ();
+        void shutdown ();
+
+        void process_reg (class simple_semaphore_t *smph_);
+        void process_unreg (class simple_semaphore_t *smph_);
+
+        //  i_poll_events implementation.
+        void in_event ();
+        void out_event ();
+        void timer_event ();
+
+        //  i_session implementation
+        void set_engine (struct i_engine *engine_);
+        //  void shutdown ();
+        bool read (struct zs_msg *msg_);
+        bool write (struct zs_msg *msg_);
+        void flush ();
+
+    private:
+
+        //  Clean-up.
+        ~connecter_t ();
+
+         enum {
+             idle,
+             waiting,
+             connecting,
+             sending
+         } state;
+
+        //  Cached pointer to the poller.
+        struct i_poller *poller;
+
+        //  Handle of the connecting socket.
+        handle_t handle;
+
+        //  Associated session. It lives in the same I/O thread.
+        class session_t *session;
+
+        //  Address to connect to.
+        std::string addr;
+
+        //  Identity of the connection.
+        std::string identity;
+
+        tcp_connecter_t tcp_connecter;
+
+        struct i_engine *engine;
+
+        connecter_t (const connecter_t&);
+        void operator = (const connecter_t&);
+    };
+
+}
+
+#endif
diff --git a/src/data_distributor.cpp b/src/data_distributor.cpp
new file mode 100644
index 0000000..8f89c46
--- /dev/null
+++ b/src/data_distributor.cpp
@@ -0,0 +1,155 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "data_distributor.hpp"
+#include "pipe_writer.hpp"
+#include "err.hpp"
+#include "session.hpp"
+#include "msg.hpp"
+
+zs::data_distributor_t::data_distributor_t () :
+    session (NULL)
+{
+}
+
+void zs::data_distributor_t::set_session (session_t *session_)
+{
+    zs_assert (!session);
+    session = session_;
+}
+
+void zs::data_distributor_t::shutdown ()
+{
+    //  No need to deallocate pipes here. They'll be deallocated during the
+    //  shutdown of the dispatcher.
+    delete this;
+}
+
+void zs::data_distributor_t::terminate ()
+{
+    //  Pipe unregisters itself during the call to terminate, so the pipes
+    //  list shinks by one in each iteration.
+    while (!pipes.empty ())
+        pipes [0]->terminate ();
+
+   delete this;
+}
+
+zs::data_distributor_t::~data_distributor_t ()
+{
+}
+
+void zs::data_distributor_t::attach_pipe (pipe_writer_t *pipe_)
+{
+    //  Associate demux with a new pipe.
+    pipe_->set_demux (this);
+    pipe_->set_index (pipes.size ());
+    pipes.push_back (pipe_);
+}
+
+void zs::data_distributor_t::detach_pipe (pipe_writer_t *pipe_)
+{
+    //  Release the reference to the pipe.
+    int index = pipe_->get_index ();
+    pipe_->set_index (-1);
+    pipes [index] = pipes.back ();
+    pipes [index]->set_index (index);
+    pipes.pop_back ();
+}
+
+bool zs::data_distributor_t::empty ()
+{
+    return pipes.empty ();
+}
+
+bool zs::data_distributor_t::send (zs_msg *msg_)
+{
+    int pipes_count = pipes.size ();
+
+    //  If there are no pipes available, simply drop the message.
+    if (pipes_count == 0) {
+        zs_msg_close (msg_);
+        zs_msg_init (msg_);
+        return true;
+    }
+
+    //  TODO: ???
+    //  First check whether all pipes are available for writing.
+//    for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it ++)
+//        if (!(*it)->check_write (msg_))
+//            return false;
+
+    //  For VSMs the copying is straighforward.
+    if (msg_->content == (zs_msg_content*) ZS_VSM) {
+        for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it ++)
+            write_to_pipe (*it, msg_);
+        zs_msg_init (msg_);
+        return true;
+    }
+
+    //  Optimisation for the case when there's only a single pipe
+    //  to send the message to - no refcount adjustment (i.e. atomic
+    //  operations) needed.
+    if (pipes_count == 1) {
+        write_to_pipe (*pipes.begin (), msg_);
+        zs_msg_init (msg_);
+        return true;
+    }
+
+    //  There are at least 2 destinations for the message. That means we have
+    //  to deal with reference counting. First add N-1 references to
+    //  the content (we are holding one reference anyway, that's why the -1).
+    if (msg_->shared)
+        msg_->content->refcnt.add (pipes_count - 1);
+    else {
+        msg_->shared = true;
+        // TODO: Add memory barrier here.
+        msg_->content->refcnt.set (pipes_count);
+    }
+
+    //  Push the message to all destinations.
+    for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it ++)
+        write_to_pipe (*it, msg_);
+
+    //  Detach the original message from the data buffer.
+    zs_msg_init (msg_);
+
+    return true;
+}
+
+void zs::data_distributor_t::flush ()
+{
+    //  Flush all pipes. If there's large number of pipes, it can be pretty
+    //  inefficient (especially if there's new message only in a single pipe).
+    //  Can it be improved?
+    for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it ++)
+        (*it)->flush ();
+}
+
+void zs::data_distributor_t::write_to_pipe (class pipe_writer_t *pipe_,
+    struct zs_msg *msg_)
+{
+    if (!pipe_->write (msg_)) {
+        //  TODO: Push gap notification to the pipe.
+        zs_assert (false);
+    }
+}
+
diff --git a/src/data_distributor.hpp b/src/data_distributor.hpp
new file mode 100644
index 0000000..239de31
--- /dev/null
+++ b/src/data_distributor.hpp
@@ -0,0 +1,70 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DATA_DISTRIBUTOR_HPP_INCLUDED__
+#define __ZS_DATA_DISTRIBUTOR_HPP_INCLUDED__
+
+#include <vector>
+
+#include <i_demux.hpp>
+
+namespace zs
+{
+
+    //  Object to distribute messages to outbound pipes.
+
+    class data_distributor_t : public i_demux
+    {
+    public:
+
+        data_distributor_t ();
+
+        //  i_demux implementation.
+        void set_session (class session_t *session_);
+        void shutdown ();
+        void terminate ();
+        void attach_pipe (class pipe_writer_t *pipe_);
+        void detach_pipe (class pipe_writer_t *pipe_);
+        bool empty ();
+        bool send (struct zs_msg *msg_);
+        void flush ();
+
+    private:
+
+        //  Clean-up.
+        ~data_distributor_t ();
+
+        //  Reference to the owner session object.
+        class session_t *session;
+
+        //  Writes the message to the pipe if possible. If it isn't, writes
+        //  a gap notification to the pipe.
+        void write_to_pipe (class pipe_writer_t *pipe_, struct zs_msg *msg_);
+
+        //  The list of outbound pipes.
+        typedef std::vector <class pipe_writer_t*> pipes_t;
+        pipes_t pipes;
+
+        data_distributor_t (const data_distributor_t&);
+        void operator = (const data_distributor_t&);
+    };
+
+}
+
+#endif
diff --git a/src/decoder.hpp b/src/decoder.hpp
new file mode 100644
index 0000000..c643df8
--- /dev/null
+++ b/src/decoder.hpp
@@ -0,0 +1,101 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DECODER_HPP_INCLUDED__
+#define __ZS_DECODER_HPP_INCLUDED__
+
+#include <stddef.h>
+#include <string.h>
+#include <algorithm>
+
+namespace zs
+{
+
+    //  Helper base class for decoders that know the amount of data to read
+    //  in advance at any moment. Knowing the amount in advance is a property
+    //  of the protocol used. Both AMQP and backend protocol are based on
+    //  size-prefixed paradigm, therefore they are using decoder_t to parse
+    //  the messages. On the other hand, XML-based transports (like XMPP or
+    //  SOAP) don't allow for knowing the size of data to read in advance and
+    //  should use different decoding algorithms.
+    //
+    //  Decoder implements the state machine that parses the incoming buffer.
+    //  Derived class should implement individual state machine actions.
+
+    template <typename T> class decoder_t
+    {
+    public:
+
+        inline decoder_t () :
+            read_ptr (NULL),
+            to_read (0),
+            next (NULL)
+        {
+        }
+
+        //  Push the binary data to the decoder. Returns number of bytes
+        // actually parsed.
+        inline size_t write (unsigned char *data_, size_t size_)
+        {
+            size_t pos = 0;
+            while (true) {
+                size_t to_copy = std::min (to_read, size_ - pos);
+                if (read_ptr) {
+                    memcpy (read_ptr, data_ + pos, to_copy);
+                    read_ptr += to_copy;
+                }
+                pos += to_copy;
+                to_read -= to_copy;
+                while (!to_read)
+                    if (!(static_cast <T*> (this)->*next) ())
+                        return pos;
+                if (pos == size_)
+                    return pos;
+            }
+        }
+
+    protected:
+
+        //  Prototype of state machine action. Action should return false if
+        //  it is unable to push the data to the system.
+        typedef bool (T::*step_t) ();
+
+        //  This function should be called from derived class to read data
+        //  from the buffer and schedule next state machine action.
+        inline void next_step (void *read_ptr_, size_t to_read_,
+            step_t next_)
+        {
+            read_ptr = (unsigned char*) read_ptr_;
+            to_read = to_read_;
+            next = next_;
+        }
+
+    private:
+
+        unsigned char *read_ptr;
+        size_t to_read;
+        step_t next;
+
+        decoder_t (const decoder_t&);
+        void operator = (const decoder_t&);
+    };
+
+}
+
+#endif
diff --git a/src/devpoll.cpp b/src/devpoll.cpp
new file mode 100644
index 0000000..6e3a8c1
--- /dev/null
+++ b/src/devpoll.cpp
@@ -0,0 +1,224 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_SOLARIS || defined ZS_HAVE_HPUX
+
+#include <sys/devpoll.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <limits.h>
+
+#include "devpoll.hpp"
+#include "err.hpp"
+#include "config.hpp"
+
+zs::devpoll_t::devpoll_t ()
+{
+    //  Get limit on open files
+    struct rlimit rl;
+    int rc = getrlimit (RLIMIT_NOFILE, &rl);
+    errno_assert (rc != -1);
+    fd_table.resize (rl.rlim_cur);
+
+    for (rlim_t i = 0; i < rl.rlim_cur; i ++)
+        fd_table [i].valid = false;
+
+    devpoll_fd = open ("/dev/poll", O_RDWR);
+    errno_assert (devpoll_fd != -1);
+}
+
+zs::devpoll_t::~devpoll_t ()
+{
+    close (devpoll_fd);
+}
+
+void zs::devpoll_t::devpoll_ctl (fd_t fd_, short events_)
+{
+    struct pollfd pfd = {fd_, events_, 0};
+    ssize_t rc = write (devpoll_fd, &pfd, sizeof pfd);
+    zs_assert (rc == sizeof pfd);
+}
+
+zs::handle_t zs::devpoll_t::add_fd (fd_t fd_, i_poll_events *reactor_)
+{
+    assert (!fd_table [fd_].valid);
+
+    fd_table [fd_].events = 0;
+    fd_table [fd_].reactor = reactor_;
+    fd_table [fd_].valid = true;
+    fd_table [fd_].accepted = false;
+
+    devpoll_ctl (fd_, 0);
+    pending_list.push_back (fd_);
+
+    //  Increase the load metric of the thread.
+    load.add (1);
+
+    handle_t handle;
+    handle.fd = fd_;
+    return handle;
+}
+
+void zs::devpoll_t::rm_fd (handle_t handle_)
+{
+    assert (fd_table [handle_.fd].valid);
+
+    devpoll_ctl (handle_.fd, POLLREMOVE);
+    fd_table [handle_.fd].valid = false;
+
+    //  Decrease the load metric of the thread.
+    load.sub (1);
+}
+
+void zs::devpoll_t::set_pollin (handle_t handle_)
+{
+    fd_t fd = handle_.fd;
+    devpoll_ctl (fd, POLLREMOVE);
+    fd_table [fd].events |= POLLIN;
+    devpoll_ctl (fd, fd_table [fd].events);
+}
+
+void zs::devpoll_t::reset_pollin (handle_t handle_)
+{
+    fd_t fd = handle_.fd;
+    devpoll_ctl (fd, POLLREMOVE);
+    fd_table [fd].events &= ~((short) POLLIN);
+    devpoll_ctl (fd, fd_table [fd].events);
+}
+
+void zs::devpoll_t::set_pollout (handle_t handle_)
+{
+    fd_t fd = handle_.fd;
+    devpoll_ctl (fd, POLLREMOVE);
+    fd_table [fd].events |= POLLOUT;
+    devpoll_ctl (fd, fd_table [fd].events);
+}
+
+void zs::devpoll_t::reset_pollout (handle_t handle_)
+{
+    fd_t fd = handle_.fd;
+    devpoll_ctl (fd, POLLREMOVE);
+    fd_table [fd].events &= ~((short) POLLOUT);
+    devpoll_ctl (fd, fd_table [fd].events);
+}
+
+void zs::devpoll_t::add_timer (i_poll_events *events_)
+{
+     timers.push_back (events_);
+}
+
+void zs::devpoll_t::cancel_timer (i_poll_events *events_)
+{
+    timers_t::iterator it = std::find (timers.begin (), timers.end (), events_);
+    if (it != timers.end ())
+        timers.erase (it);
+}
+
+int zs::devpoll_t::get_load ()
+{
+    return load.get ();
+}
+
+void zs::devpoll_t::start ()
+{
+    worker.start (worker_routine, this);
+}
+
+void zs::devpoll_t::stop ()
+{
+    stopping = true;
+}
+
+void zs::devpoll_t::join ()
+{
+    worker.stop ();
+}
+
+bool zs::devpoll_t::loop ()
+{
+    //  According to the poll(7d) man page, we can retrieve
+    //  no more then (OPEN_MAX - 1) events.
+    int nfds = std::min (max_io_events, OPEN_MAX - 1);
+
+    while (!stopping) {
+
+        struct pollfd ev_buf [max_io_events];
+        struct dvpoll poll_req;
+
+        for (pending_list_t::size_type i = 0; i < pending_list.size (); i ++)
+            fd_table [pending_list [i]].accepted = true;
+        pending_list.clear ();
+
+        poll_req.dp_fds = &ev_buf [0];
+        poll_req.dp_nfds = nfds;
+        poll_req.dp_timeout = timers.empty () ? -1 : max_timer_period;
+
+        //  Wait for events.
+        int n = ioctl (devpoll_fd, DP_POLL, &poll_req);
+        if (n == -1 && errno == EINTR)
+            continue;
+        errno_assert (n != -1);
+
+        //  Handle timer.
+        if (!n) {
+
+            //  Use local list of timers as timer handlers may fill new timers
+            //  into the original array.
+            timers_t t;
+            std::swap (timers, t);
+
+            //  Trigger all the timers.
+            for (timers_t::iterator it = t.begin (); it != t.end (); it ++)
+                (*it)->timer_event ();
+
+            continue;
+        }
+
+        for (int i = 0; i < n; i ++) {
+
+            fd_entry_t *fd_ptr = &fd_table [ev_buf [i].fd];
+            if (!fd_ptr->valid || !fd_ptr->accepted)
+                continue;
+            if (ev_buf [i].revents & (POLLERR | POLLHUP))
+                fd_ptr->reactor->in_event ();
+            if (!fd_ptr->valid || !fd_ptr->accepted)
+                continue;
+            if (ev_buf [i].revents & POLLOUT)
+                fd_ptr->reactor->out_event ();
+            if (!fd_ptr->valid || !fd_ptr->accepted)
+                continue;
+            if (ev_buf [i].revents & POLLIN)
+                fd_ptr->reactor->in_event ();
+        }
+    }
+}
+
+void zs::devpoll_t::worker_routine (void *arg_)
+{
+    ((devpoll_t*) arg_)->loop ();
+}
+
+#endif
diff --git a/src/devpoll.hpp b/src/devpoll.hpp
new file mode 100644
index 0000000..56b3b25
--- /dev/null
+++ b/src/devpoll.hpp
@@ -0,0 +1,110 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DEVPOLL_HPP_INCLUDED__
+#define __ZS_DEVPOLL_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_SOLARIS || ZS_HAVE_HPUX
+
+#include <vector>
+
+#include "i_poller.hpp"
+#include "fd.hpp"
+#include "thread.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  Implements socket polling mechanism using the Solaris-specific
+    //  "/dev/poll" interface.
+
+    class devpoll_t : public i_poller
+    {
+    public:
+
+        devpoll_t ();
+        virtual ~devpoll_t ();
+
+        //  i_poller implementation.
+        handle_t add_fd (fd_t fd_, i_poll_events *events_);
+        void rm_fd (handle_t handle_);
+        void set_pollin (handle_t handle_);
+        void reset_pollin (handle_t handle_);
+        void set_pollout (handle_t handle_);
+        void reset_pollout (handle_t handle_);
+        void add_timer (i_poll_events *events_);
+        void cancel_timer (i_poll_events *events_);
+        int get_load ();
+        void start ();
+        void stop ();
+        void join ();
+
+    private:
+
+        //  Main worker thread routine.
+        static void worker_routine (void *arg_);
+
+        //  Main event loop.
+        void loop ();
+
+        //  File descriptor referring to "/dev/poll" pseudo-device.
+        fd_t devpoll_fd;
+
+        struct fd_entry_t
+        {
+            short events;
+            struct i_poll_events *reactor;
+            bool valid;
+            bool accepted;
+        };
+
+        std::vector <fd_entry_t> fd_table;
+
+        typedef std::vector <fd_t> pending_list_t;
+        pending_list_t pending_list;
+
+        //  Pollset manipulation function.
+        void devpoll_ctl (fd_t fd_, short events_);
+
+        //  List of all the engines waiting for the timer event.
+        typedef std::vector <struct i_poll_events*> timers_t;
+        timers_t timers;
+
+        //  If true, thread is in the process of shutting down.
+        bool stopping;
+
+        //  Handle of the physical thread doing the I/O work.
+        thread_t worker;
+
+        //  Load of the poller. Currently number of file descriptors
+        //  registered with the poller.
+        atomic_counter_t load;
+
+        devpoll_t (const devpoll_t&);
+        void operator = (const devpoll_t&);
+    };
+
+}
+
+#endif
+
+#endif
diff --git a/src/dispatcher.cpp b/src/dispatcher.cpp
new file mode 100644
index 0000000..c468857
--- /dev/null
+++ b/src/dispatcher.cpp
@@ -0,0 +1,266 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "dispatcher.hpp"
+#include "app_thread.hpp"
+#include "io_thread.hpp"
+#include "platform.hpp"
+#include "err.hpp"
+#include "pipe.hpp"
+#include "pipe_reader.hpp"
+#include "pipe_writer.hpp"
+#include "session.hpp"
+#include "i_api.hpp"
+
+#if defined ZS_HAVE_WINDOWS
+#include "windows.h"
+#endif
+
+zs::dispatcher_t::dispatcher_t (int app_threads_, int io_threads_)
+{
+#ifdef ZS_HAVE_WINDOWS
+    //  Intialise Windows sockets. Note that WSAStartup can be called multiple
+    //  times given that WSACleanup will be called for each WSAStartup.
+    WORD version_requested = MAKEWORD (2, 2);
+    WSADATA wsa_data;
+    int rc = WSAStartup (version_requested, &wsa_data);
+    zs_assert (rc == 0);
+    zs_assert (LOBYTE (wsa_data.wVersion) == 2 &&
+        HIBYTE (wsa_data.wVersion) == 2);
+#endif
+
+    //  Create application thread proxies.
+    for (int i = 0; i != app_threads_; i++) {
+        app_thread_t *app_thread = new app_thread_t (this, i);
+        zs_assert (app_thread);
+        app_threads.push_back (app_thread);
+        signalers.push_back (app_thread->get_signaler ());
+    }
+
+    //  Create I/O thread objects.
+    for (int i = 0; i != io_threads_; i++) {
+        io_thread_t *io_thread = new io_thread_t (this, i + app_threads_);
+        zs_assert (io_thread);
+        io_threads.push_back (io_thread);
+        signalers.push_back (io_thread->get_signaler ());
+    }
+
+    //  Create command pipe matrix.
+    command_pipes = new command_pipe_t [signalers.size () * signalers.size ()];
+    zs_assert (command_pipes);
+
+    //  Launch I/O threads.
+    for (int i = 0; i != io_threads_; i++)
+        io_threads [i]->start ();
+}
+
+void zs::dispatcher_t::shutdown ()
+{
+     delete this;
+}
+
+zs::dispatcher_t::~dispatcher_t ()
+{
+    //  Ask I/O threads to terminate.
+    for (io_threads_t::size_type i = 0; i != io_threads.size (); i++)
+        io_threads [i]->stop ();
+
+    //  Wait till I/O threads actually terminate.
+    for (io_threads_t::size_type i = 0; i != io_threads.size (); i++)
+        io_threads [i]->join ();
+
+    //  At this point the current thread is the only thread with access to
+    //  our internal data. Deallocation will be done exclusively in this thread.
+    for (app_threads_t::size_type i = 0; i != app_threads.size (); i++)
+        app_threads [i]->shutdown ();
+    for (io_threads_t::size_type i = 0; i != io_threads.size (); i++)
+        io_threads [i]->shutdown ();
+
+    delete [] command_pipes;
+
+    //  Deallocate all the pipes, pipe readers and pipe writers.
+    for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it++) {
+        delete it->pipe;
+        delete it->reader;
+        delete it->writer;
+    }
+
+#ifdef ZS_HAVE_WINDOWS
+    //  On Windows, uninitialise socket layer.
+    int rc = WSACleanup ();
+    wsa_assert (rc != SOCKET_ERROR);
+#endif
+}
+
+int zs::dispatcher_t::thread_slot_count ()
+{
+    return signalers.size ();
+}
+
+zs::i_api *zs::dispatcher_t::create_socket (int type_)
+{
+    threads_sync.lock ();
+    app_thread_t *thread = choose_app_thread ();
+    if (!thread) {
+        threads_sync.unlock ();
+        return NULL;
+    }
+    i_api *s = thread->create_socket (type_);
+    threads_sync.unlock ();
+    return s;
+}
+
+zs::app_thread_t *zs::dispatcher_t::choose_app_thread ()
+{
+    //  Check whether thread ID is already assigned. If so, return it.
+    for (app_threads_t::size_type i = 0; i != app_threads.size (); i++)
+        if (app_threads [i]->is_current ())
+            return app_threads [i];
+
+    //  Check whether there's an unused thread slot in the dispatcher.
+    for (app_threads_t::size_type i = 0; i != app_threads.size (); i++)
+        if (app_threads [i]->make_current ())
+            return app_threads [i];
+
+    //  Thread limit was exceeded.
+    errno = EMFILE;
+    return NULL;
+}
+
+zs::io_thread_t *zs::dispatcher_t::choose_io_thread (uint64_t taskset_)
+{
+    zs_assert (io_threads.size () > 0);
+
+    //  Find the I/O thread with minimum load.
+    int min_load = io_threads [0]->get_load ();
+    io_threads_t::size_type result = 0;
+    for (io_threads_t::size_type i = 1; i != io_threads.size (); i++) {
+        if (!taskset_ || (taskset_ & (uint64_t (1) << i))) {
+            int load = io_threads [i]->get_load ();
+            if (load < min_load) {
+                min_load = load;
+                result = i;
+            }
+        }
+    }
+
+    return io_threads [result];
+}
+
+void zs::dispatcher_t::create_pipe (object_t *reader_parent_,
+    object_t *writer_parent_, uint64_t hwm_, uint64_t lwm_,
+    pipe_reader_t **reader_, pipe_writer_t **writer_)
+{
+    //  Create the pipe, reader & writer triple.
+    pipe_t *pipe = new pipe_t;
+    zs_assert (pipe);
+    pipe_reader_t *reader = new pipe_reader_t (reader_parent_, pipe,
+        hwm_, lwm_);
+    zs_assert (reader);
+    pipe_writer_t *writer = new pipe_writer_t (writer_parent_, pipe, reader,
+        hwm_, lwm_);
+    zs_assert (writer);
+    reader->set_peer (writer);
+
+    //  Store the pipe in the repository.
+    pipe_info_t info = {pipe, reader, writer};
+    pipes_sync.lock ();
+    pipe->set_index (pipes.size ());
+    pipes.push_back (info);
+    pipes_sync.unlock ();
+
+    *reader_ = reader;
+    *writer_ = writer;
+}
+
+void zs::dispatcher_t::destroy_pipe (pipe_t *pipe_)
+{
+    //  Remove the pipe from the repository.
+    pipe_info_t info;
+    pipes_sync.lock ();
+    pipes_t::size_type i = pipe_->get_index ();
+    info = pipes [i];
+    pipes [i] = pipes.back ();
+    pipes.pop_back ();
+    pipes_sync.unlock ();
+
+    //  Deallocate the pipe and associated pipe reader & pipe writer.
+    zs_assert (info.pipe == pipe_);
+    delete info.pipe;
+    delete info.reader;
+    delete info.writer;
+}
+
+int zs::dispatcher_t::register_inproc_endpoint (const char *endpoint_,
+    session_t *session_)
+{
+   inproc_endpoint_sync.lock ();
+   inproc_endpoints_t::iterator it = inproc_endpoints.find (endpoint_);
+
+   if (it != inproc_endpoints.end ()) {
+       inproc_endpoint_sync.unlock ();
+       errno = EADDRINUSE;
+       return -1;
+   }
+
+   inproc_endpoints.insert (std::make_pair (endpoint_, session_));
+
+   inproc_endpoint_sync.unlock ();
+   return 0;
+}
+
+zs::object_t *zs::dispatcher_t::get_inproc_endpoint (const char *endpoint_)
+{
+    inproc_endpoint_sync.lock ();
+    inproc_endpoints_t::iterator it = inproc_endpoints.find (endpoint_);
+
+    if (it == inproc_endpoints.end ()) {
+        inproc_endpoint_sync.unlock ();
+        errno = EADDRNOTAVAIL;
+        return NULL;
+    }
+
+    it->second->inc_seqnum ();
+    object_t *session = it->second;
+
+    inproc_endpoint_sync.unlock ();
+    return session;
+}
+
+void zs::dispatcher_t::unregister_inproc_endpoints (session_t *session_)
+{
+    inproc_endpoint_sync.lock ();
+
+    //  Remove the connection from the repository.
+    //  TODO: Yes, the algorithm has O(n^2) complexity. Should be O(log n).
+    for (inproc_endpoints_t::iterator it = inproc_endpoints.begin ();
+          it != inproc_endpoints.end ();) {
+        if (it->second == session_) {
+            inproc_endpoints.erase (it);
+            it = inproc_endpoints.begin ();
+        }
+        else
+            it++;
+    }
+        
+    inproc_endpoint_sync.unlock ();
+}
+
diff --git a/src/dispatcher.hpp b/src/dispatcher.hpp
new file mode 100644
index 0000000..05d2c49
--- /dev/null
+++ b/src/dispatcher.hpp
@@ -0,0 +1,170 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DISPATCHER_HPP_INCLUDED__
+#define __ZS_DISPATCHER_HPP_INCLUDED__
+
+#include <vector>
+#include <map>
+#include <string>
+
+#include "i_signaler.hpp"
+#include "ypipe.hpp"
+#include "command.hpp"
+#include "config.hpp"
+#include "mutex.hpp"
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    //  Dispatcher implements bidirectional thread-safe passing of commands
+    //  between N threads. It consists of a ypipes to pass commands and
+    //  signalers to wake up the receiver thread when new commands are
+    //  available. Note that dispatcher is inefficient for passing messages
+    //  within a thread (sender thread = receiver thread). The optimisation is
+    //  not part of the class and should be implemented by individual threads
+    //  (presumably by calling the command handling function directly).
+    
+    class dispatcher_t
+    {
+    public:
+
+        //  Create the dispatcher object. Matrix of pipes to communicate between
+        //  each socket and each I/O thread is created along with appropriate
+        //  signalers.
+        dispatcher_t (int app_threads_, int io_threads_);
+
+        //  To be called to terminate the whole infrastructure (zs_term).
+        void shutdown ();
+
+        //  Create a socket engine.
+        struct i_api *create_socket (int type_);
+
+        //  Returns number of thread slots in the dispatcher. To be used by
+        //  individual threads to find out how many distinct signals can be
+        //  received.
+        int thread_slot_count ();
+
+        //  Write command to the dispatcher.
+        inline void write (int source_, int destination_,
+            const command_t &command_)
+        {
+            command_pipe_t &pipe =
+                command_pipes [source_ * signalers.size () + destination_];
+            pipe.write (command_);
+            if (!pipe.flush ())
+                signalers [destination_]->signal (source_);
+        }
+
+        //  Read command from the dispatcher. Returns false if there is no
+        //  command available.
+        inline bool read (int source_,  int destination_, command_t *command_)
+        {
+            return command_pipes [source_ * signalers.size () +
+                destination_].read (command_);
+        }
+
+        //  Creates new pipe.
+        void create_pipe (class object_t *reader_parent_,
+            class object_t *writer_parent_, uint64_t hwm_, uint64_t lwm_,
+            class pipe_reader_t **reader_, class pipe_writer_t **writer_);
+
+        //  Deallocates the pipe.
+        void destroy_pipe (class pipe_t *pipe_);
+
+        //  Registers existing session object as an inproc endpoint.
+        int register_inproc_endpoint (const char *endpoint_,
+            class session_t *session_);
+
+        //  Retrieves an inproc endpoint. Increments the command sequence number
+        //  of the object by one. Caller is thus bound to send the command
+        //  to the connection after invoking this function. Returns NULL if
+        //  the endpoint doesn't exist.
+        class object_t *get_inproc_endpoint (const char *endpoint_);
+
+        //  Removes all the inproc endpoints associated with the given session
+        //  object from the global repository.
+        void unregister_inproc_endpoints (class session_t *session_);
+
+        //  Returns the I/O thread that is the least busy at the moment.
+        //  Taskset specifies which I/O threads are eligible (0 = all).
+        class io_thread_t *choose_io_thread (uint64_t taskset_);
+
+    private:
+
+        //  Clean-up.
+        ~dispatcher_t ();
+
+        //  Returns the app thread associated with the current thread.
+        //  NULL if we are out of app thread slots.
+        class app_thread_t *choose_app_thread ();
+
+        //  Application threads.
+        typedef std::vector <class app_thread_t*> app_threads_t;
+        app_threads_t app_threads;
+
+        //  I/O threads.
+        typedef std::vector <class io_thread_t*> io_threads_t;
+        io_threads_t io_threads;
+
+        //  Signalers for both application and I/O threads.
+        std::vector <i_signaler*> signalers;
+
+        //  Pipe to hold the commands.
+        typedef ypipe_t <command_t, true,
+            command_pipe_granularity> command_pipe_t;
+
+        //  NxN matrix of command pipes.
+        command_pipe_t *command_pipes;
+
+        //  Synchronisation of accesses to shared thread data.
+        mutex_t threads_sync;
+
+        //  Global repository of pipes. It's used only on terminal shutdown
+        //  to deallocate all the pipes irrespective of whether they are
+        //  referenced from pipe_reader, pipe_writer or both.
+        struct pipe_info_t
+        {
+            class pipe_t *pipe;
+            class pipe_reader_t *reader;
+            class pipe_writer_t *writer;
+        };
+        typedef std::vector <pipe_info_t> pipes_t;
+        pipes_t pipes;
+
+        //  Synchronisation of access to global repository of pipes.
+        mutex_t pipes_sync;
+
+        //  Global repository of available inproc endpoints.
+        typedef std::map <std::string, class session_t*> inproc_endpoints_t;
+        inproc_endpoints_t inproc_endpoints;
+
+        //  Synchronisation of access to the global repository
+        //  of inproc endpoints.
+        mutex_t inproc_endpoint_sync;
+
+        dispatcher_t (const dispatcher_t&);
+        void operator = (const dispatcher_t&);
+    };
+    
+}
+
+#endif
+
diff --git a/src/dummy_aggregator.cpp b/src/dummy_aggregator.cpp
new file mode 100644
index 0000000..ef0cea6
--- /dev/null
+++ b/src/dummy_aggregator.cpp
@@ -0,0 +1,111 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "dummy_aggregator.hpp"
+#include "err.hpp"
+#include "pipe_reader.hpp"
+#include "session.hpp"
+
+//  Swaps pipes at specified indices. 
+#define swap_pipes(i1_, i2_) \
+    std::swap (pipes [i1_], pipes [i2_]);\
+    pipes [i1_]->set_index (i1_);\
+    pipes [i2_]->set_index (i2_);
+
+zs::dummy_aggregator_t::dummy_aggregator_t () :
+    session (NULL),
+    pipe (NULL),
+    active (false)
+{
+}
+
+void zs::dummy_aggregator_t::set_session (session_t *session_)
+{
+    zs_assert (!session);
+    session = session_;
+}
+
+void zs::dummy_aggregator_t::shutdown ()
+{
+    //  No need to deallocate the pipe here. It'll be deallocated during the
+    //  shutdown of the dispatcher.
+    delete this;
+}
+
+void zs::dummy_aggregator_t::terminate ()
+{
+    if (pipe)
+        pipe->terminate ();
+
+   delete this;
+}
+
+zs::dummy_aggregator_t::~dummy_aggregator_t ()
+{
+}
+
+void zs::dummy_aggregator_t::attach_pipe (pipe_reader_t *pipe_)
+{
+    zs_assert (!pipe);
+    pipe = pipe_;
+    active = true;
+
+    //  Associate new pipe with the mux object.
+    pipe_->set_mux (this);
+    session->revive ();
+}
+
+void zs::dummy_aggregator_t::detach_pipe (pipe_reader_t *pipe_)
+{
+    zs_assert (pipe == pipe_);
+    deactivate (pipe_);
+    pipe = NULL;
+}
+
+bool zs::dummy_aggregator_t::empty ()
+{
+    return pipe == NULL;
+}
+
+bool zs::dummy_aggregator_t::recv (zs_msg *msg_)
+{
+    //  Deallocate old content of the message.
+    zs_msg_close (msg_);
+        
+    //  Try to read from the pipe.
+    if (pipe && pipe->read (msg_))
+        return true;
+
+    //  No message is available. Initialise the output parameter
+    //  to be a 0-byte message.
+    zs_msg_init (msg_);
+    return false;
+}
+
+void zs::dummy_aggregator_t::deactivate (pipe_reader_t *pipe_)
+{
+    active = false;
+}
+
+void zs::dummy_aggregator_t::reactivate (pipe_reader_t *pipe_)
+{
+    active = true;
+}
diff --git a/src/dummy_aggregator.hpp b/src/dummy_aggregator.hpp
new file mode 100644
index 0000000..ab5bcb9
--- /dev/null
+++ b/src/dummy_aggregator.hpp
@@ -0,0 +1,73 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DUMMY_AGGREGATOR_HPP_INCLUDED__
+#define __ZS_DUMMY_AGGREGATOR_HPP_INCLUDED__
+
+#include <vector>
+
+#include "i_mux.hpp"
+
+namespace zs
+{
+
+    //  Fake message aggregator. There can be at most one pipe bound to it,
+    //  so there's no real aggregation going on. However, it is more efficient
+    //  than a real aggregator. It's intended to be used in the contexts
+    //  where business logic ensures there'll be at most one pipe bound.
+
+    class dummy_aggregator_t : public i_mux
+    {
+    public:
+
+        dummy_aggregator_t ();
+
+        //  i_mux interface implementation.
+        void set_session (session_t *session_);
+        void shutdown ();
+        void terminate ();
+        void attach_pipe (class pipe_reader_t *pipe_);
+        void detach_pipe (class pipe_reader_t *pipe_);
+        bool empty ();
+        void deactivate (class pipe_reader_t *pipe_);
+        void reactivate (class pipe_reader_t *pipe_);
+        bool recv (struct zs_msg *msg_);
+
+
+    private:
+
+        //  Clean-up.
+        ~dummy_aggregator_t ();
+
+        //  Reference to the owner session object.
+        class session_t *session;
+
+        //  The single pipe bound.
+        class pipe_reader_t *pipe;
+
+        //  If true, the pipe is active.
+        bool active;
+
+        dummy_aggregator_t (const dummy_aggregator_t&);
+        void operator = (const dummy_aggregator_t&);
+    };
+
+}
+
+#endif
diff --git a/src/dummy_distributor.cpp b/src/dummy_distributor.cpp
new file mode 100644
index 0000000..58cadfe
--- /dev/null
+++ b/src/dummy_distributor.cpp
@@ -0,0 +1,85 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "dummy_distributor.hpp"
+#include "pipe_writer.hpp"
+#include "err.hpp"
+#include "session.hpp"
+#include "msg.hpp"
+
+zs::dummy_distributor_t::dummy_distributor_t () :
+    session (NULL)
+{
+}
+
+void zs::dummy_distributor_t::set_session (session_t *session_)
+{
+    zs_assert (!session);
+    session = session_;
+}
+
+void zs::dummy_distributor_t::shutdown ()
+{
+    //  No need to deallocate pipe here. It'll be deallocated during the
+    //  shutdown of the dispatcher.
+    delete this;
+}
+
+void zs::dummy_distributor_t::terminate ()
+{
+   if (pipe)
+       pipe->terminate ();
+
+   delete this;
+}
+
+zs::dummy_distributor_t::~dummy_distributor_t ()
+{
+}
+
+void zs::dummy_distributor_t::attach_pipe (pipe_writer_t *pipe_)
+{
+    zs_assert (!pipe);
+    pipe = pipe_;
+}
+
+void zs::dummy_distributor_t::detach_pipe (pipe_writer_t *pipe_)
+{
+    zs_assert (pipe == pipe_);
+    pipe = NULL;
+}
+
+bool zs::dummy_distributor_t::empty ()
+{
+    return pipe == NULL;
+}
+
+bool zs::dummy_distributor_t::send (zs_msg *msg_)
+{
+    return pipe && pipe->write (msg_);
+}
+
+void zs::dummy_distributor_t::flush ()
+{
+    if (pipe)
+        pipe->flush ();
+}
+
diff --git a/src/dummy_distributor.hpp b/src/dummy_distributor.hpp
new file mode 100644
index 0000000..c200ad6
--- /dev/null
+++ b/src/dummy_distributor.hpp
@@ -0,0 +1,68 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_DUMMY_DISTRIBUTOR_HPP_INCLUDED__
+#define __ZS_DUMMY_DISTRIBUTOR_HPP_INCLUDED__
+
+#include <vector>
+
+#include <i_demux.hpp>
+
+namespace zs
+{
+
+    //  Fake message distributor. There can be only one pipe bound to it
+    //  so there no real distribution going on. However, it is more efficient
+    //  than a real distributor and should be used where business logic
+    //  ensures there'll be at most one pipe bound.
+
+    class dummy_distributor_t : public i_demux
+    {
+    public:
+
+        dummy_distributor_t ();
+
+        //  i_demux implementation.
+        void set_session (class session_t *session_);
+        void shutdown ();
+        void terminate ();
+        void attach_pipe (class pipe_writer_t *pipe_);
+        void detach_pipe (class pipe_writer_t *pipe_);
+        bool empty ();
+        bool send (struct zs_msg *msg_);
+        void flush ();
+
+    private:
+
+        //  Clean-up.
+        ~dummy_distributor_t ();
+
+        //  Reference to the owner session object.
+        class session_t *session;
+
+        //  The bound pipe.
+        class pipe_writer_t *pipe;
+
+        dummy_distributor_t (const dummy_distributor_t&);
+        void operator = (const dummy_distributor_t&);
+    };
+
+}
+
+#endif
diff --git a/src/encoder.hpp b/src/encoder.hpp
new file mode 100644
index 0000000..1241873
--- /dev/null
+++ b/src/encoder.hpp
@@ -0,0 +1,108 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ENCODER_HPP_INCLUDED__
+#define __ZS_ENCODER_HPP_INCLUDED__
+
+#include <stddef.h>
+#include <string.h>
+#include <algorithm>
+
+namespace zs
+{
+
+    //  Helper base class for encoders. It implements the state machine that
+    //  fills the outgoing buffer. Derived classes should implement individual
+    //  state machine actions.
+
+    template <typename T> class encoder_t
+    {
+    public:
+
+        inline encoder_t ()
+        {
+        }
+
+        //  The function tries to fill the supplied chunk by binary data.
+        //  Returns the size of data actually filled in. If offset is not
+        //  NULL, it is filled by offset of the first message in the batch.
+        //  If there's no beginning of a message in the batch, offset is
+        //  set to -1.
+        inline size_t read (unsigned char *data_, size_t size_,
+            int *offset_ = NULL)
+        {
+            int offset = -1;
+            size_t pos = 0;
+
+            while (pos < size_) {
+                if (to_write) {
+
+                    size_t to_copy = std::min (to_write, size_ - pos);
+                    memcpy (data_ + pos, write_pos, to_copy);
+                    pos += to_copy;
+                    write_pos += to_copy;
+                    to_write -= to_copy;
+                }
+                else {
+                    bool more = (static_cast <T*> (this)->*next) ();
+                    if (beginning && offset == -1) {
+                        offset = pos;
+                        beginning = false;
+                    }
+                    if (!more)
+                        break;
+                }
+            }
+
+            if (offset_)
+                *offset_ = offset;
+
+            return pos;
+        }
+    protected:
+
+        //  Prototype of state machine action.
+        typedef bool (T::*step_t) ();
+
+        //  This function should be called from derived class to write the data
+        //  to the buffer and schedule next state machine action. Set beginning
+        //  to true when you are writing first byte of a message.
+        inline void next_step (void *write_pos_, size_t to_write_,
+            step_t next_, bool beginning_)
+        {
+            write_pos = (unsigned char*) write_pos_;
+            to_write = to_write_;
+            next = next_;
+            beginning = beginning_;
+        }
+
+    private:
+
+        unsigned char *write_pos;
+        size_t to_write;
+        step_t next;
+        bool beginning;
+
+        encoder_t (const encoder_t&);
+        void operator = (const encoder_t&);
+    };
+
+}
+
+#endif
diff --git a/src/epoll.cpp b/src/epoll.cpp
new file mode 100644
index 0000000..a9780d2
--- /dev/null
+++ b/src/epoll.cpp
@@ -0,0 +1,214 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_LINUX
+
+#include <sys/epoll.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <algorithm>
+
+#include "epoll.hpp"
+#include "err.hpp"
+#include "config.hpp"
+#include "i_poll_events.hpp"
+
+zs::epoll_t::epoll_t () :
+    stopping (false)
+{
+    epoll_fd = epoll_create (1);
+    errno_assert (epoll_fd != -1);
+}
+
+zs::epoll_t::~epoll_t ()
+{
+    close (epoll_fd);
+
+    for (retired_t::iterator it = retired.begin (); it != retired.end (); it ++)
+        delete *it;
+}
+
+zs::handle_t zs::epoll_t::add_fd (fd_t fd_, i_poll_events *events_)
+{
+    poll_entry_t *pe = new poll_entry_t;
+    zs_assert (pe != NULL);
+
+    //  The memset is not actually needed. It's here to prevent debugging
+    //  tools to complain about using uninitialised memory.
+    memset (pe, 0, sizeof (poll_entry_t));
+
+    pe->fd = fd_;
+    pe->ev.events = 0;
+    pe->ev.data.ptr = pe;
+    pe->events = events_;
+
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_ADD, fd_, &pe->ev);
+    errno_assert (rc != -1);
+
+    //  Increase the load metric of the thread.
+    load.add (1);
+
+    handle_t handle;
+    handle.ptr = pe;
+    return handle;
+}
+
+void zs::epoll_t::rm_fd (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_DEL, pe->fd, &pe->ev);
+    errno_assert (rc != -1);
+    pe->fd = retired_fd;
+    retired.push_back (pe);
+
+    //  Decrease the load metric of the thread.
+    load.sub (1);
+}
+
+void zs::epoll_t::set_pollin (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->ev.events |= EPOLLIN;
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
+    errno_assert (rc != -1);
+}
+
+void zs::epoll_t::reset_pollin (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->ev.events &= ~((short) EPOLLIN);
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
+    errno_assert (rc != -1);
+}
+
+void zs::epoll_t::set_pollout (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->ev.events |= EPOLLOUT;
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
+    errno_assert (rc != -1);
+}
+
+void zs::epoll_t::reset_pollout (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->ev.events &= ~((short) EPOLLOUT);
+    int rc = epoll_ctl (epoll_fd, EPOLL_CTL_MOD, pe->fd, &pe->ev);
+    errno_assert (rc != -1);
+}
+
+void zs::epoll_t::add_timer (i_poll_events *events_)
+{
+     timers.push_back (events_);
+}
+
+void zs::epoll_t::cancel_timer (i_poll_events *events_)
+{
+    timers_t::iterator it = std::find (timers.begin (), timers.end (), events_);
+    if (it == timers.end ())
+        return;
+    timers.erase (it);
+}
+
+int zs::epoll_t::get_load ()
+{
+    return load.get ();
+}
+
+void zs::epoll_t::start ()
+{
+    worker.start (worker_routine, this);
+}
+
+void zs::epoll_t::stop ()
+{
+    stopping = true;
+}
+
+void zs::epoll_t::join ()
+{
+    worker.stop ();
+}
+
+void zs::epoll_t::loop ()
+{
+    epoll_event ev_buf [max_io_events];
+
+    while (!stopping) {
+
+        //  Wait for events.
+        int n;
+        while (true) {
+            n = epoll_wait (epoll_fd, &ev_buf [0], max_io_events,
+                timers.empty () ? -1 : max_timer_period);
+            if (!(n == -1 && errno == EINTR)) {
+                errno_assert (n != -1);
+                break;
+            }
+        }
+
+        //  Handle timer.
+        if (!n) {
+
+            //  Use local list of timers as timer handlers may fill new timers
+            //  into the original array.
+            timers_t t;
+            std::swap (timers, t);
+
+            //  Trigger all the timers.
+            for (timers_t::iterator it = t.begin (); it != t.end (); it ++)
+                (*it)->timer_event ();
+
+            continue;
+        }
+
+        for (int i = 0; i < n; i ++) {
+            poll_entry_t *pe = ((poll_entry_t*) ev_buf [i].data.ptr);
+
+            if (pe->fd == retired_fd)
+                continue;
+            if (ev_buf [i].events & (EPOLLERR | EPOLLHUP))
+                pe->events->in_event ();
+            if (pe->fd == retired_fd)
+               continue;
+            if (ev_buf [i].events & EPOLLOUT)
+                pe->events->out_event ();
+            if (pe->fd == retired_fd)
+                continue;
+            if (ev_buf [i].events & EPOLLIN)
+                pe->events->in_event ();
+        }
+
+        //  Destroy retired event sources.
+        for (retired_t::iterator it = retired.begin (); it != retired.end ();
+              it ++)
+            delete *it;
+        retired.clear ();
+    }
+}
+
+void zs::epoll_t::worker_routine (void *arg_)
+{
+    ((epoll_t*) arg_)->loop ();
+}
+
+#endif
diff --git a/src/epoll.hpp b/src/epoll.hpp
new file mode 100644
index 0000000..a3f5168
--- /dev/null
+++ b/src/epoll.hpp
@@ -0,0 +1,107 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_EPOLL_HPP_INCLUDED__
+#define __ZS_EPOLL_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_LINUX
+
+#include <vector>
+#include <sys/epoll.h>
+
+#include "i_poller.hpp"
+//#include "i_poll_events.hpp"
+#include "fd.hpp"
+#include "thread.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  This class implements socket polling mechanism using the Linux-specific
+    //  epoll mechanism.
+
+    class epoll_t : public i_poller
+    {
+    public:
+
+        epoll_t ();
+        virtual ~epoll_t ();
+
+        //  i_poller implementation.
+        handle_t add_fd (fd_t fd_, i_poll_events *events_);
+        void rm_fd (handle_t handle_);
+        void set_pollin (handle_t handle_);
+        void reset_pollin (handle_t handle_);
+        void set_pollout (handle_t handle_);
+        void reset_pollout (handle_t handle_);
+        void add_timer (i_poll_events *events_);
+        void cancel_timer (i_poll_events *events_);
+        int get_load ();
+        void start ();
+        void stop ();
+        void join ();
+
+    private:
+
+        //  Main worker thread routine.
+        static void worker_routine (void *arg_);
+
+        //  Main event loop.
+        void loop ();
+
+        //  Main epoll file descriptor
+        fd_t epoll_fd;
+
+        struct poll_entry_t
+        {
+            fd_t fd;
+            epoll_event ev;
+            struct i_poll_events *events;
+        };
+
+        //  List of retired event sources.
+        typedef std::vector <poll_entry_t*> retired_t;
+        retired_t retired;
+
+        //  List of all the engines waiting for the timer event.
+        typedef std::vector <struct i_poll_events*> timers_t;
+        timers_t timers;
+
+        //  If true, thread is in the process of shutting down.
+        bool stopping;
+
+        //  Handle of the physical thread doing the I/O work.
+        thread_t worker;
+
+        //  Load of the poller. Currently number of file descriptors
+        //  registered with the poller.
+        atomic_counter_t load;
+
+        epoll_t (const epoll_t&);
+        void operator = (const epoll_t&);
+    };
+
+}
+
+#endif
+
+#endif
diff --git a/src/err.cpp b/src/err.cpp
new file mode 100644
index 0000000..92a03ba
--- /dev/null
+++ b/src/err.cpp
@@ -0,0 +1,146 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "err.hpp"
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+
+const char *zs::wsa_error()
+{
+    int errcode = WSAGetLastError ();
+    //  TODO: This is not a generic way to handle this...
+    if (errcode == WSAEWOULDBLOCK)
+        return NULL;
+
+    return
+        (errcode == WSABASEERR) ?
+            "No Error" : 
+        (errcode == WSAEINTR) ?
+            "Interrupted system call" : 
+        (errcode == WSAEBADF) ?
+            "Bad file number" : 
+        (errcode == WSAEACCES) ?
+            "Permission denied" : 
+        (errcode == WSAEFAULT) ?
+            "Bad address" : 
+        (errcode == WSAEINVAL) ?
+            "Invalid argument" : 
+        (errcode == WSAEMFILE) ?
+            "Too many open files" : 
+        (errcode == WSAEWOULDBLOCK) ?
+            "Operation would block" : 
+        (errcode == WSAEINPROGRESS) ?
+            "Operation now in progress" : 
+        (errcode == WSAEALREADY) ?
+            "Operation already in progress" : 
+        (errcode == WSAENOTSOCK) ?
+            "Socket operation on non-socket" : 
+        (errcode == WSAEDESTADDRREQ) ?
+            "Destination address required" : 
+        (errcode == WSAEMSGSIZE) ?
+            "Message too long" : 
+        (errcode == WSAEPROTOTYPE) ?
+            "Protocol wrong type for socket" : 
+        (errcode == WSAENOPROTOOPT) ?
+            "Bad protocol option" : 
+        (errcode == WSAEPROTONOSUPPORT) ?
+            "Protocol not supported" : 
+        (errcode == WSAESOCKTNOSUPPORT) ?
+            "Socket type not supported" : 
+        (errcode == WSAEOPNOTSUPP) ?
+            "Operation not supported on socket" : 
+        (errcode == WSAEPFNOSUPPORT) ?
+            "Protocol family not supported" : 
+        (errcode == WSAEAFNOSUPPORT) ?
+            "Address family not supported by protocol family" : 
+        (errcode == WSAEADDRINUSE) ?
+            "Address already in use" : 
+        (errcode == WSAEADDRNOTAVAIL) ?
+            "Can't assign requested address" : 
+        (errcode == WSAENETDOWN) ?
+            "Network is down" : 
+        (errcode == WSAENETUNREACH) ?
+            "Network is unreachable" : 
+        (errcode == WSAENETRESET) ?
+            "Net dropped connection or reset" : 
+        (errcode == WSAECONNABORTED) ?
+            "Software caused connection abort" : 
+        (errcode == WSAECONNRESET) ?
+            "Connection reset by peer" : 
+        (errcode == WSAENOBUFS) ?
+            "No buffer space available" : 
+        (errcode == WSAEISCONN) ?
+            "Socket is already connected" : 
+        (errcode == WSAENOTCONN) ?
+            "Socket is not connected" : 
+        (errcode == WSAESHUTDOWN) ?
+            "Can't send after socket shutdown" : 
+        (errcode == WSAETOOMANYREFS) ?
+            "Too many references can't splice" : 
+        (errcode == WSAETIMEDOUT) ?
+            "Connection timed out" : 
+        (errcode == WSAECONNREFUSED) ?
+            "Connection refused" : 
+        (errcode == WSAELOOP) ?
+            "Too many levels of symbolic links" : 
+        (errcode == WSAENAMETOOLONG) ?
+            "File name too long" : 
+        (errcode == WSAEHOSTDOWN) ?
+            "Host is down" : 
+        (errcode == WSAEHOSTUNREACH) ?
+            "No Route to Host" : 
+        (errcode == WSAENOTEMPTY) ?
+            "Directory not empty" : 
+        (errcode == WSAEPROCLIM) ?
+            "Too many processes" : 
+        (errcode == WSAEUSERS) ?
+            "Too many users" : 
+        (errcode == WSAEDQUOT) ?
+            "Disc Quota Exceeded" : 
+        (errcode == WSAESTALE) ?
+            "Stale NFS file handle" : 
+        (errcode == WSAEREMOTE) ?
+            "Too many levels of remote in path" : 
+        (errcode == WSASYSNOTREADY) ?
+            "Network SubSystem is unavailable" : 
+        (errcode == WSAVERNOTSUPPORTED) ?
+            "WINSOCK DLL Version out of range" : 
+        (errcode == WSANOTINITIALISED) ?
+            "Successful WSASTARTUP not yet performed" : 
+        (errcode == WSAHOST_NOT_FOUND) ?
+            "Host not found" : 
+        (errcode == WSATRY_AGAIN) ?
+            "Non-Authoritative Host not found" : 
+        (errcode == WSANO_RECOVERY) ?
+            "Non-Recoverable errors: FORMERR REFUSED NOTIMP" : 
+        (errcode == WSANO_DATA) ?
+            "Valid name no data record of requested" :
+        "error not defined"; 
+}
+void zs::win_error (char *buffer_, size_t buffer_size_)
+{
+    DWORD errcode = GetLastError ();
+    DWORD rc = FormatMessageA (FORMAT_MESSAGE_FROM_SYSTEM |
+        FORMAT_MESSAGE_IGNORE_INSERTS, NULL, errcode, MAKELANGID(LANG_NEUTRAL,
+        SUBLANG_DEFAULT), buffer_, buffer_size_, NULL );
+    zs_assert (rc);
+}
+
+#endif
diff --git a/src/err.hpp b/src/err.hpp
new file mode 100644
index 0000000..657eb3d
--- /dev/null
+++ b/src/err.hpp
@@ -0,0 +1,90 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ERR_HPP_INCLUDED__
+#define __ZS_ERR_HPP_INCLUDED__
+
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#else
+#include <netdb.h>
+#endif
+
+#ifdef ZS_HAVE_WINDOWS
+
+namespace zs
+{
+
+    const char *wsa_error ();
+    void win_error (char *buffer_, size_t buffer_size_);
+  
+}
+
+//  Provides convenient way to check WSA-style errors on Windows.
+#define wsa_assert(x) do { if (!(x)){\
+    const char *errstr = zs::wsa_error ();\
+    if (errstr != NULL) {\
+    fprintf (stderr, "Assertion failed: %s (%s:%d)\n", errstr, \
+        __FILE__, __LINE__);\
+        abort ();\
+    }\
+}} while (false)
+
+//  Provides convenient way to check GetLastError-style errors on Windows.
+#define win_assert(x) do { if (!(x)) {\
+    char errstr [256];\
+    zs::win_error (errstr, 256);\
+    fprintf (stderr, "Assertion failed: %s (%s:%d)\n", errstr, \
+        __FILE__, __LINE__);\
+    abort ();\
+}} while (false)
+
+#endif
+
+//  This macro works in exactly the same way as the normal assert. It is used
+//  in its stead because standard assert on Win32 in broken - it prints nothing
+//  when used within the scope of JNI library.
+#define zs_assert(x) do { if (!(x)){\
+    fprintf (stderr, "Assertion failed: %s (%s:%d)\n", #x, \
+        __FILE__, __LINE__);\
+        abort ();\
+}} while (false) 
+
+//  Provides convenient way to check for errno-style errors.
+#define errno_assert(x) do { if (!(x)) {\
+    perror (NULL);\
+    fprintf (stderr, "%s (%s:%d)\n", #x, __FILE__, __LINE__);\
+    abort ();\
+}} while (false)
+
+// Provides convenient way to check for errors from getaddrinfo.
+#define gai_assert(x) do { if (x) {\
+    const char *errstr = gai_strerror (x);\
+    fprintf (stderr, "%s (%s:%d)\n", errstr, __FILE__, __LINE__);\
+    abort ();\
+}} while (false)
+
+#endif
diff --git a/src/fair_aggregator.cpp b/src/fair_aggregator.cpp
new file mode 100644
index 0000000..65bfac0
--- /dev/null
+++ b/src/fair_aggregator.cpp
@@ -0,0 +1,143 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "fair_aggregator.hpp"
+#include "err.hpp"
+#include "pipe_reader.hpp"
+#include "session.hpp"
+
+//  Swaps pipes at specified indices. 
+#define swap_pipes(i1_, i2_) \
+    std::swap (pipes [i1_], pipes [i2_]);\
+    pipes [i1_]->set_index (i1_);\
+    pipes [i2_]->set_index (i2_);
+
+zs::fair_aggregator_t::fair_aggregator_t () :
+    session (NULL),
+    active (0),
+    current (0)
+{
+}
+
+void zs::fair_aggregator_t::set_session (session_t *session_)
+{
+    zs_assert (!session);
+    session = session_;
+}
+
+void zs::fair_aggregator_t::shutdown ()
+{
+    //  No need to deallocate pipes here. They'll be deallocated during the
+    //  shutdown of the dispatcher.
+    delete this;
+}
+
+void zs::fair_aggregator_t::terminate ()
+{
+    //  Pipe unregisters itself during the call to terminate, so the pipes
+    //  list shinks by one in each iteration.
+    while (!pipes.empty ())
+        pipes [0]->terminate ();
+
+   delete this;
+}
+
+zs::fair_aggregator_t::~fair_aggregator_t ()
+{
+}
+
+void zs::fair_aggregator_t::attach_pipe (pipe_reader_t *pipe_)
+{
+    //  Associate new pipe with the mux object.
+    pipe_->set_mux (this);
+    pipes.push_back (pipe_);
+    active++;
+    if (pipes.size () > active)
+        swap_pipes (pipes.size () - 1, active - 1);
+    if (active == 1)
+        session->revive ();
+}
+
+void zs::fair_aggregator_t::detach_pipe (pipe_reader_t *pipe_)
+{
+    //  Move the pipe from the list of active pipes to the list of idle pipes.
+    deactivate (pipe_);
+            
+    //  Move the pipe to the end of the idle list and remove it.
+    swap_pipes (pipe_->get_index (), pipes.size () - 1);
+    pipes.pop_back ();
+}
+
+bool zs::fair_aggregator_t::empty ()
+{
+    return pipes.empty ();
+}
+
+bool zs::fair_aggregator_t::recv (zs_msg *msg_)
+{
+    //  Deallocate old content of the message.
+    zs_msg_close (msg_);
+
+    //  O(1) fair queueing. Round-robin over the active pipes to get
+    //  next message.
+    for (pipes_t::size_type i = active; i != 0; i--) {
+
+        //  Update current.
+        current = (current + 1) % active;
+        
+        //  Try to read from current.
+        if (pipes [current]->read (msg_))
+            return true;
+    }
+
+    //  No message is available. Initialise the output parameter
+    //  to be a 0-byte message.
+    zs_msg_init (msg_);
+    return false;
+}
+
+void zs::fair_aggregator_t::deactivate (pipe_reader_t *pipe_)
+{
+    int index = pipe_->get_index ();
+
+    //  Suspend an active pipe.
+    swap_pipes (index, active - 1);
+    active--;
+
+    //  If the deactiveted pipe is the current one, shift the current one pipe
+    //  backwards so that the pipe that replaced the deactiveted one will be
+    //  processed immediately rather than skipped.
+    if (index == (int) current) {
+        index--;
+        if (index == -1)
+            index = active - 1;
+        current = index;
+    }
+}
+
+void zs::fair_aggregator_t::reactivate (pipe_reader_t *pipe_)
+{
+    //  Revive an idle pipe.
+    swap_pipes (pipe_->get_index (), active);
+    active++;
+    if (active == 1)
+        session->revive ();
+}
diff --git a/src/fair_aggregator.hpp b/src/fair_aggregator.hpp
new file mode 100644
index 0000000..9e6c3bb
--- /dev/null
+++ b/src/fair_aggregator.hpp
@@ -0,0 +1,77 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_FAIR_AGGREGATOR_HPP_INCLUDED__
+#define __ZS_FAIR_AGGREGATOR_HPP_INCLUDED__
+
+#include <vector>
+
+#include "i_mux.hpp"
+
+namespace zs
+{
+
+    //  Object to aggregate messages from inbound pipes.
+
+    class fair_aggregator_t : public i_mux
+    {
+    public:
+
+        fair_aggregator_t ();
+
+        //  i_mux interface implementation.
+        void set_session (session_t *session_);
+        void shutdown ();
+        void terminate ();
+        void attach_pipe (class pipe_reader_t *pipe_);
+        void detach_pipe (class pipe_reader_t *pipe_);
+        bool empty ();
+        void deactivate (class pipe_reader_t *pipe_);
+        void reactivate (class pipe_reader_t *pipe_);
+        bool recv (struct zs_msg *msg_);
+
+
+    private:
+
+        //  Clean-up.
+        ~fair_aggregator_t ();
+
+        //  Reference to the owner session object.
+        class session_t *session;
+
+        //  The list of inbound pipes. The active pipes are occupying indices
+        //  from 0 to active-1. Suspended pipes occupy indices from 'active'
+        //  to the end of the array.
+        typedef std::vector <class pipe_reader_t*> pipes_t;
+        pipes_t pipes;
+
+        //  The number of active pipes.
+        pipes_t::size_type active;
+
+        //  Pipe to retrieve next message from. The messages are retrieved
+        //  from the pipes in round-robin fashion (a.k.a. fair queueing).
+        pipes_t::size_type current;
+
+        fair_aggregator_t (const fair_aggregator_t&);
+        void operator = (const fair_aggregator_t&);
+    };
+
+}
+
+#endif
diff --git a/src/fd.hpp b/src/fd.hpp
new file mode 100644
index 0000000..4d45ed2
--- /dev/null
+++ b/src/fd.hpp
@@ -0,0 +1,44 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_FD_HPP_INCLUDED__
+#define __ZS_FD_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#endif
+
+namespace zs
+{
+#ifdef _MSC_VER
+#if (_MSC_VER <= 1400)
+    typedef UINT_PTR fd_t;
+    enum {retired_fd = (fd_t)(~0)}
+#else
+    typedef SOCKET fd_t;
+    enum {retired_fd = INVALID_SOCKET};
+#endif
+#else
+    typedef int fd_t;
+    enum {retired_fd = -1};
+#endif
+}
+#endif
diff --git a/src/fd_signaler.cpp b/src/fd_signaler.cpp
new file mode 100644
index 0000000..005dd86
--- /dev/null
+++ b/src/fd_signaler.cpp
@@ -0,0 +1,278 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "fd_signaler.hpp"
+#include "platform.hpp"
+#include "err.hpp"
+#include "fd.hpp"
+
+#if defined ZS_HAVE_OPENVMS
+#include <netinet/tcp.h>
+#elif defined ZS_HAVE_WINDOWS 
+#include "windows.hpp"
+#else
+#include <unistd.h>
+#include <fcntl.h>
+#endif
+
+#if defined ZS_HAVE_EVENTFD
+
+#include <sys/eventfd.h>
+
+zs::fd_signaler_t::fd_signaler_t ()
+{
+    //  Create eventfd object.
+    fd = eventfd (0, 0);
+    errno_assert (fd != -1);
+
+    //  Set to non-blocking mode.
+    int flags = fcntl (fd, F_GETFL, 0);
+    if (flags == -1)
+        flags = 0;
+    int rc = fcntl (fd, F_SETFL, flags | O_NONBLOCK);
+    errno_assert (rc != -1);
+}
+
+zs::fd_signaler_t::~fd_signaler_t ()
+{
+    int rc = close (fd);
+    errno_assert (rc != -1);
+}
+
+void zs::fd_signaler_t::signal (int signal_)
+{
+    zs_assert (signal_ >= 0 && signal_ < 64);
+    signals_t inc = 1;
+    inc <<= signal_;
+    ssize_t sz = write (fd, &inc, sizeof (signals_t));
+    errno_assert (sz == sizeof (signals_t));
+}
+
+zs::fd_signaler_t::signals_t zs::fd_signaler_t::check ()
+{
+    signals_t val;
+    ssize_t sz = read (fd, &val, sizeof (signals_t));
+    if (sz == -1 && (errno == EAGAIN || errno == EWOULDBLOCK ||
+          errno == EINTR))
+        return 0;
+    errno_assert (sz != -1);
+    return val;
+}
+
+zs::fd_t zs::fd_signaler_t::get_fd ()
+{
+    return fd;
+}
+
+#elif defined ZS_HAVE_WINDOWS
+
+zs::fd_signaler_t::fd_signaler_t ()
+{
+    struct sockaddr_in addr;
+    SOCKET listener;
+    int addrlen = sizeof (addr);
+           
+    w = INVALID_SOCKET; 
+    r = INVALID_SOCKET;
+    
+    fd_t rcs = (listener = socket (AF_INET, SOCK_STREAM, 0));
+    wsa_assert (rcs != INVALID_SOCKET);
+
+    memset (&addr, 0, sizeof (addr));
+    addr.sin_family = AF_INET;
+    resolve_ip_hostname (&addr, "127.0.0.1:0");
+            
+    int rc = bind (listener, (const struct sockaddr*) &addr, sizeof (addr));
+    wsa_assert (rc != SOCKET_ERROR);
+
+    rc = getsockname (listener, (struct sockaddr*) &addr, &addrlen);
+    wsa_assert (rc != SOCKET_ERROR);
+            
+    //  Listen for incomming connections.
+    rc = listen (listener, 1);
+    wsa_assert (rc != SOCKET_ERROR);
+                     
+    //  Create the socket.
+    w = WSASocket (AF_INET, SOCK_STREAM, 0, NULL, 0,  0);
+    wsa_assert (w != INVALID_SOCKET);
+                      
+    //  Connect to the remote peer.
+    rc = connect (w, (sockaddr *) &addr, sizeof (addr));
+    wsa_assert (rc != SOCKET_ERROR);
+                                    
+    //  Accept connection from w
+    r = accept (listener, NULL, NULL);
+    wsa_assert (r != INVALID_SOCKET);
+            
+    rc = closesocket (listener);
+    wsa_assert (rc != SOCKET_ERROR);
+}
+
+zs::fd_signaler_t::~fd_signaler_t ()
+{
+    int rc = closesocket (w);
+    wsa_assert (rc != SOCKET_ERROR);
+
+    rc = closesocket (r);
+    wsa_assert (rc != SOCKET_ERROR);
+}
+
+void zs::fd_signaler_t::signal (int signal_)
+{
+    zs_assert (signal_ >= 0 && signal_ < 64);
+    char c = (char) signal_;
+    int rc = send (w, &c, 1, 0);
+    win_assert (rc != SOCKET_ERROR);
+}
+
+zs::fd_signaler_t::signals_t zs::fd_signaler_t::check ()
+{
+    char buffer [32];      
+    int nbytes = recv (r, buffer, 32, 0);
+    win_assert (nbytes != -1);
+
+    signals_t signals = 0;
+    for (int pos = 0; pos != nbytes; pos++) {
+        zs_assert (buffer [pos] < 64);
+        signals |= (1 << (buffer [pos]));
+    }
+    return signals;
+}
+
+zs::fd_t zs::fd_signaler_t::get_fd ()
+{
+    return r;
+}
+
+#else
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+zs::fd_signaler_t::fd_signaler_t ()
+{
+    int sv [2];
+    int rc = socketpair (AF_UNIX, SOCK_STREAM, 0, sv);
+    errno_assert (rc == 0);
+    w = sv [0];
+    r = sv [1];
+                      
+    //  Set to non-blocking mode.
+    int flags = fcntl (r, F_GETFL, 0);
+    if (flags == -1)
+        flags = 0;
+    rc = fcntl (r, F_SETFL, flags | O_NONBLOCK);
+    errno_assert (rc != -1);
+}
+
+zs::fd_signaler_t::~fd_signaler_t ()
+{
+    close (w);
+    close (r);
+}
+
+void zs::fd_signaler_t::signal (int signal_)
+{
+    zs_assert (signal_ >= 0 && signal_ < 64);
+    unsigned char c = (unsigned char) signal_;
+    ssize_t nbytes = send (w, &c, 1, 0);
+    errno_assert (nbytes == 1);
+}
+
+zs::fd_signaler_t::signals_t zs::fd_signaler_t::check ()
+{
+    unsigned char buffer [32];
+    ssize_t nbytes = recv (r, buffer, 32, 0);
+    errno_assert (nbytes != -1);
+    signals_t signals = 0;
+    for (int pos = 0; pos != nbytes; pos ++) {
+        zs_assert (buffer [pos] < 64);
+        signals |= (1 << (buffer [pos]));
+    }
+    return signals;
+}
+
+zs::fd_t zs::fd_signaler_t::get_fd ()
+{
+    return r;
+}
+
+#endif
+
+#if defined ZS_HAVE_OPENVMS
+
+int zs::fd_signaler_t::socketpair (int domain_, int type_, int protocol_,
+    int sv_ [2])
+{
+    int listener;
+    sockaddr_in lcladdr;
+    socklen_t lcladdr_len;
+    int rc;
+    int on = 1;
+
+    zs_assert (type_ == SOCK_STREAM);
+
+    //  Fill in the localhost address (127.0.0.1).
+    memset (&lcladdr, 0, sizeof (lcladdr));
+    lcladdr.sin_family = AF_INET;
+    lcladdr.sin_addr.s_addr = 0x0100007f;
+    lcladdr.sin_port = INADDR_ANY;
+
+    listener = socket (AF_INET, SOCK_STREAM, 0);
+    errno_assert (listener != -1);
+
+    rc = setsockopt (listener, IPPROTO_TCP, TCP_NODELAY, &on, sizeof (on));
+    errno_assert (rc != -1);
+
+    rc = setsockopt (listener, IPPROTO_TCP, TCP_NODELACK, &on, sizeof (on));
+    errno_assert (rc != -1);
+
+    rc = bind(listener, (struct sockaddr*) &lcladdr, sizeof (lcladdr));
+    errno_assert (rc != -1);
+        
+    lcladdr_len = sizeof (lcladdr);
+
+    rc = getsockname (listener, (struct sockaddr*) &lcladdr, &lcladdr_len);
+    errno_assert (rc != -1);
+
+    rc = listen (listener, 1);
+    errno_assert (rc != -1);
+
+    sv_ [0] = socket (AF_INET, SOCK_STREAM, 0);
+    errno_assert (rc != -1);
+
+    rc = setsockopt (sv_ [0], IPPROTO_TCP, TCP_NODELAY, &on, sizeof (on));
+    errno_assert (rc != -1);
+
+    rc = setsockopt (sv_ [0], IPPROTO_TCP, TCP_NODELACK, &on, sizeof (on));
+    errno_assert (rc != -1);
+
+    rc = connect (sv_ [0], (struct sockaddr*) &lcladdr, sizeof (lcladdr));
+    errno_assert (rc != -1);
+
+    sv_ [1] = accept (listener, NULL, NULL);
+    errno_assert (sv_ [1] != -1);
+
+    close (listener);
+
+    return 0;
+}
+
+#endif
+
diff --git a/src/fd_signaler.hpp b/src/fd_signaler.hpp
new file mode 100644
index 0000000..34c5e8c
--- /dev/null
+++ b/src/fd_signaler.hpp
@@ -0,0 +1,92 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_FD_SIGNALER_HPP_INCLUDED__
+#define __ZS_FD_SIGNALER_HPP_INCLUDED__
+
+#include "platform.hpp"
+#include "i_signaler.hpp"
+#include "fd.hpp"
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    //  This object can be used to send individual signals from one thread to
+    //  another. The specific of this pipe is that it has associated file
+    //  descriptor and so it can be polled on. Same signal cannot be sent twice
+    //  unless signals are retrieved by the reader side in the meantime.
+
+    class fd_signaler_t : public i_signaler
+    {
+    public:
+
+        typedef uint64_t signals_t;
+
+        //  Initialise the object.
+        fd_signaler_t ();
+
+        //  Destroy the object.
+        ~fd_signaler_t ();
+
+        //  Send specific signal.
+        void signal (int signal_);
+
+        //  Retrieves signals. Returns a set of signals in form of a bitmap.
+        //  Signal with index 0 corresponds to value 1, index 1 to value 2,
+        //  index 2 to value 4 etc. If there is no signal available,
+        //  it returns zero immediately.
+        signals_t check ();
+
+        //  Get the file descriptor associated with the object.
+        fd_t get_fd ();
+
+    private:
+
+#if defined ZMQ_HAVE_OPENVMS
+
+         //  Whilst OpenVMS supports socketpair - it maps to AF_INET only.
+         //  Further, it does not set the socket options TCP_NODELAY and
+         //  TCP_NODELACK which can lead to performance problems. We'll
+         //  overload the socketpair function for this class.
+         //
+         //  The bug will be fixed in V5.6 ECO4 and beyond.  In the
+         //  meantime, we'll create the socket pair manually.
+         static int socketpair (int domain_, int type_, int protocol_,
+             int sv_ [2]);
+
+#endif
+
+#if defined ZS_HAVE_EVENTFD
+        //  Eventfd descriptor.
+        fd_t fd;
+#else
+        //  Write & read end of the socketpair.
+        fd_t w;
+        fd_t r;
+#endif
+
+        //  Disable copying of fd_signeler object.
+        fd_signaler_t (const fd_signaler_t&);
+        void operator = (const fd_signaler_t&);
+    };
+
+}
+
+#endif
diff --git a/src/i_api.hpp b/src/i_api.hpp
new file mode 100644
index 0000000..4dccd9e
--- /dev/null
+++ b/src/i_api.hpp
@@ -0,0 +1,39 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_API_HPP_INCLUDED__
+#define __ZS_I_API_HPP_INCLUDED__
+
+namespace zs
+{
+
+    struct i_api
+    {
+        virtual int bind (const char *addr_, struct zs_opts *opts_) = 0;
+        virtual int connect (const char *addr_, struct zs_opts *opts_) = 0;
+        virtual int subscribe (const char *criteria_) = 0;
+        virtual int send (struct zs_msg *msg_, int flags_) = 0;
+        virtual int flush () = 0;
+        virtual int recv (struct zs_msg *msg_, int flags_) = 0;
+        virtual int close () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_demux.hpp b/src/i_demux.hpp
new file mode 100644
index 0000000..edded1e
--- /dev/null
+++ b/src/i_demux.hpp
@@ -0,0 +1,56 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_DEMUX_HPP_INCLUDED__
+#define __ZS_I_DEMUX_HPP_INCLUDED__
+
+namespace zs
+{
+
+    struct i_demux
+    {
+        //  Attaches mux to a particular session.
+        virtual void set_session (class session_t *session_) = 0;
+
+        //  To be called when the whole infrastrucure is being closed (zs_term).
+        virtual void shutdown () = 0;
+
+        //  To be called when session is being closed.
+        virtual void terminate () = 0;
+
+        //  Adds new pipe to the demux to send messages to.
+        virtual void attach_pipe (class pipe_writer_t *pipe_) = 0;
+
+        //  Removes pipe from the demux.
+        virtual void detach_pipe (class pipe_writer_t *pipe_) = 0;
+
+        //  Returns true if there's no pipe attached.
+        virtual bool empty () = 0;
+
+        //  Sends the message. Returns false if the message cannot be sent
+        //  because the pipes are full.
+        virtual bool send (struct zs_msg *msg_) = 0;
+
+        //  Flushes messages downstream.
+        virtual void flush () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_engine.hpp b/src/i_engine.hpp
new file mode 100644
index 0000000..bade705
--- /dev/null
+++ b/src/i_engine.hpp
@@ -0,0 +1,53 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_ENGINE_HPP_INCLUDED__
+#define __ZS_I_ENGINE_HPP_INCLUDED__
+
+namespace zs
+{
+
+    //  Generic interface to access engines from MD objects.
+
+    struct i_engine
+    {
+        //  Attach the engine with specified context.
+        virtual void attach (struct i_poller *poller_,
+            struct i_session *session_) = 0;
+
+        //  Detach the engine from the current context.
+        virtual void detach () = 0;
+
+        //  Notify the engine that new messages are available.
+        virtual void revive () = 0;
+
+        //  Called by session when it decides the engine
+        //  should terminate itself.
+        virtual void schedule_terminate () = 0;
+
+        //  Called by normal object termination process.
+        virtual void terminate () = 0;
+
+        //  To be called by MD when terminal shutdown (zs_term) is in progress.
+        virtual void shutdown () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_mux.hpp b/src/i_mux.hpp
new file mode 100644
index 0000000..4c8ef72
--- /dev/null
+++ b/src/i_mux.hpp
@@ -0,0 +1,59 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_MUX_HPP_INCLUDED__
+#define __ZS_I_MUX_HPP_INCLUDED__
+
+namespace zs
+{
+
+    struct i_mux
+    {
+        //  Attaches mux to a particular session.
+        virtual void set_session (class session_t *session_) = 0;
+
+        //  To be called when the whole infrastrucure is being closed (zs_term).
+        virtual void shutdown () = 0;
+
+        //  To be called when session is being closed.
+        virtual void terminate () = 0;
+
+        //  Adds new pipe to the mux to send messages to.
+        virtual void attach_pipe (class pipe_reader_t *pipe_) = 0;
+
+        //  Removes pipe from the mux.
+        virtual void detach_pipe (class pipe_reader_t *pipe_) = 0;
+
+        //  Returns true if there's no pipe attached.
+        virtual bool empty () = 0;
+
+        //  Shifts the pipe from active to passive state and vice versa.
+        //  TODO: Check whether state transitions cannot be done by
+        //  mux object itself without a need for external APIs.
+        virtual void deactivate (class pipe_reader_t *pipe_) = 0;
+        virtual void reactivate (class pipe_reader_t *pipe_) = 0;
+
+        //  Receives a message. Returns false when there is no message
+        //  to receive.
+        virtual bool recv (struct zs_msg *msg_) = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_poll_events.hpp b/src/i_poll_events.hpp
new file mode 100644
index 0000000..5189dad
--- /dev/null
+++ b/src/i_poll_events.hpp
@@ -0,0 +1,45 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_POLL_EVENTS_HPP_INCLUDED__
+#define __ZS_I_POLL_EVENTS_HPP_INCLUDED__
+
+namespace zs
+{
+
+    //  Virtual interface to be exposed by object that want to be notified
+    //  about events on file descriptors.
+
+    struct i_poll_events
+    {
+        virtual ~i_poll_events () {};
+
+        //  Called by I/O thread when file descriptor is ready for reading.
+        virtual void in_event () = 0;
+
+        //  Called by I/O thread when file descriptor is ready for writing.
+        virtual void out_event () = 0;
+
+        //  Called when timer expires.
+        virtual void timer_event () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_poller.hpp b/src/i_poller.hpp
new file mode 100644
index 0000000..c226dfa
--- /dev/null
+++ b/src/i_poller.hpp
@@ -0,0 +1,89 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_POLLER_HPP_INCLUDED__
+#define __ZS_I_POLLER_HPP_INCLUDED__
+
+#include "fd.hpp"
+
+namespace zs
+{
+
+    union handle_t
+    {
+        fd_t fd;
+        void *ptr;
+    };
+
+    //  Virtual interface to be used when polling on file descriptors.
+
+    struct i_poller
+    {
+        virtual ~i_poller () {};
+
+        //  Add file descriptor to the polling set. Return handle
+        //  representing the descriptor. 'events' interface will be used
+        //  to invoke callback functions when event occurs.
+        virtual handle_t add_fd (fd_t fd_, struct i_poll_events *events_) = 0;
+
+        //  Remove file descriptor identified by handle from the polling set.
+        virtual void rm_fd (handle_t handle_) = 0;
+
+        //  Start polling for input from socket.
+        virtual void set_pollin (handle_t handle_) = 0;
+
+        //  Stop polling for input from socket.
+        virtual void reset_pollin (handle_t handle_) = 0;
+
+        //  Start polling for availability of the socket for writing.
+        virtual void set_pollout (handle_t handle_) = 0;
+
+        //  Stop polling for availability of the socket for writing.
+        virtual void reset_pollout (handle_t handle_) = 0;
+
+        //  Ask to be notified after some time. Actual interval varies between
+        //  0 and max_timer_period ms. Timer is destroyed once it expires or,
+        //  optionally, when cancel_timer is called.
+        virtual void add_timer (struct i_poll_events *events_) = 0;
+
+        //  Cancel the timer set by add_timer method.
+        virtual void cancel_timer (struct i_poll_events *events_) = 0;
+
+        //  Returns load experienced by the I/O thread. Currently it's number
+        //  of file descriptors handled by the poller, in the future we may
+        //  use a metric taking actual traffic on the individual sockets into
+        //  account.
+        virtual int get_load () = 0;
+
+        //  Start the execution of the underlying I/O thread.
+        //  This method is called from a foreign thread.
+        virtual void start () = 0;
+
+        //  Ask underlying I/O thread to stop. This method is called from
+        //  underlying thread (callback from io_thread object).
+        virtual void stop () = 0;
+
+        //  Wait for termination of undelying I/O thread.
+        //  This method is called from a foreign thread.
+        virtual void join () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_session.hpp b/src/i_session.hpp
new file mode 100644
index 0000000..8a8c40f
--- /dev/null
+++ b/src/i_session.hpp
@@ -0,0 +1,37 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_SESSION_HPP_INCLUDED__
+#define __ZS_I_SESSION_HPP_INCLUDED__
+
+namespace zs
+{
+
+    struct i_session
+    {
+        virtual void set_engine (struct i_engine *engine_) = 0;
+        virtual void shutdown () = 0;
+        virtual bool read (struct zs_msg *msg_) = 0;
+        virtual bool write (struct zs_msg *msg_) = 0;
+        virtual void flush () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_signaler.hpp b/src/i_signaler.hpp
new file mode 100644
index 0000000..f6f0398
--- /dev/null
+++ b/src/i_signaler.hpp
@@ -0,0 +1,38 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_SIGNALER_HPP_INCLUDED__
+#define __ZS_I_SIGNALER_HPP_INCLUDED__
+
+namespace zs
+{
+    //  Virtual interface used to send signals. Individual implementations
+    //  may restrict the number of possible signal types to send.
+
+    struct i_signaler
+    {
+        virtual ~i_signaler () {};
+
+        //  Send a signal with a specific ID.
+        virtual void signal (int signal_) = 0;
+    };
+
+}
+
+#endif
diff --git a/src/i_thread.hpp b/src/i_thread.hpp
new file mode 100644
index 0000000..fdb60c5
--- /dev/null
+++ b/src/i_thread.hpp
@@ -0,0 +1,38 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_I_THREAD_HPP_INCLUDED__
+#define __ZS_I_THREAD_HPP_INCLUDED__
+
+namespace zs
+{
+
+    //  Interface used by session object to communicate with the thread
+    //  it belongs to.
+
+    struct i_thread
+    {
+        virtual void attach_session (class session_t *session_) = 0;
+        virtual void detach_session (class session_t *session_) = 0;
+        virtual struct i_poller *get_poller () = 0;
+    };
+
+}
+
+#endif
diff --git a/src/io_object.cpp b/src/io_object.cpp
new file mode 100644
index 0000000..01388eb
--- /dev/null
+++ b/src/io_object.cpp
@@ -0,0 +1,37 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "io_object.hpp"
+#include "io_thread.hpp"
+#include "i_poller.hpp"
+
+zs::io_object_t::io_object_t (io_thread_t *thread_) :
+    object_t (thread_),
+    thread (thread_)
+{
+}
+
+zs::io_object_t::~io_object_t ()
+{
+}
+
+zs::i_poller *zs::io_object_t::get_poller ()
+{
+    return thread->get_poller ();
+}
diff --git a/src/io_object.hpp b/src/io_object.hpp
new file mode 100644
index 0000000..766c008
--- /dev/null
+++ b/src/io_object.hpp
@@ -0,0 +1,51 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_IO_OBJECT_HPP_INCLUDED__
+#define __ZS_IO_OBJECT_HPP_INCLUDED__
+
+#include "object.hpp"
+
+namespace zs
+{
+
+    //  All objects running within the context of an I/O thread should be
+    //  derived from this class to allow owning application threads to
+    //  destroy them.
+
+    class io_object_t : public object_t
+    {
+    public:
+
+        io_object_t (class io_thread_t *thread_);
+        ~io_object_t ();
+
+        virtual void terminate () = 0;
+        virtual void shutdown () = 0;
+
+        struct i_poller *get_poller ();
+
+    private:
+ 
+        class io_thread_t *thread;
+    };
+
+}
+
+#endif
diff --git a/src/io_thread.cpp b/src/io_thread.cpp
new file mode 100644
index 0000000..7994874
--- /dev/null
+++ b/src/io_thread.cpp
@@ -0,0 +1,177 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "io_thread.hpp"
+#include "command.hpp"
+#include "platform.hpp"
+#include "err.hpp"
+#include "command.hpp"
+#include "epoll.hpp"
+#include "poll.hpp"
+#include "select.hpp"
+#include "devpoll.hpp"
+#include "kqueue.hpp"
+#include "dispatcher.hpp"
+#include "session.hpp"
+#include "simple_semaphore.hpp"
+#include "session.hpp"
+
+zs::io_thread_t::io_thread_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    object_t (dispatcher_, thread_slot_)
+{
+#if defined ZS_FORCE_SELECT
+    poller = new select_t;
+#elif defined ZS_FORCE_POLL
+    poller = new poll_t;
+#elif defined ZS_FORCE_EPOLL
+    poller = new epoll_t;
+#elif defined ZS_FORCE_DEVPOLL
+    poller = new devpoll_t;
+#elif defined ZS_FORCE_KQUEUE
+    poller = new kqueue_t;
+#elif defined ZS_HAVE_LINUX
+    poller = new epoll_t;
+#elif defined ZS_HAVE_WINDOWS
+    poller = new select_t;
+#elif defined ZS_HAVE_FREEBSD
+    poller = new kqueue_t;
+#elif defined ZS_HAVE_OPENBSD
+    poller = new kqueue_t;
+#elif defined ZS_HAVE_SOLARIS
+    poller = new devpoll_t;
+#elif defined ZS_HAVE_OSX
+    poller = new kqueue_t;
+#elif defined ZS_HAVE_QNXNTO
+    poller = new poll_t;
+#elif defined ZS_HAVE_AIX
+    poller = new poll_t;
+#elif defined ZS_HAVE_HPUX
+    poller = new devpoll_t;
+#elif defined ZS_HAVE_OPENVMS
+    poller = new select_t;
+#else
+#error Unsupported platform
+#endif
+    zs_assert (poller);
+
+    signaler_handle = poller->add_fd (signaler.get_fd (), this);
+    poller->set_pollin (signaler_handle);
+}
+
+void zs::io_thread_t::shutdown ()
+{
+    //  Deallocate all the sessions associated with the thread.
+    while (!sessions.empty ())
+        sessions [0]->shutdown ();
+
+    delete this;
+}
+
+zs::io_thread_t::~io_thread_t ()
+{
+    delete poller;
+}
+
+void zs::io_thread_t::start ()
+{
+    //  Start the underlying I/O thread.
+    poller->start ();
+}
+
+void zs::io_thread_t::stop ()
+{
+    send_stop ();
+}
+
+void zs::io_thread_t::join ()
+{
+    poller->join ();
+}
+
+zs::i_signaler *zs::io_thread_t::get_signaler ()
+{
+    return &signaler;
+}
+
+int zs::io_thread_t::get_load ()
+{
+    return poller->get_load ();
+}
+
+void zs::io_thread_t::in_event ()
+{
+    //  Find out which threads are sending us commands.
+    fd_signaler_t::signals_t signals = signaler.check ();
+    zs_assert (signals);
+
+    //  Iterate through all the threads in the process and find out
+    //  which of them sent us commands.
+    int slot_count = thread_slot_count ();
+    for (int source_thread_slot = 0;
+          source_thread_slot != slot_count; source_thread_slot++) {
+        if (signals & (fd_signaler_t::signals_t (1) << source_thread_slot)) {
+
+            //  Read all the commands from particular thread.
+            command_t cmd;
+            while (dispatcher->read (source_thread_slot, thread_slot, &cmd))
+                cmd.destination->process_command (cmd);
+        }
+    }
+}
+
+void zs::io_thread_t::out_event ()
+{
+    //  We are never polling for POLLOUT here. This function is never called.
+    zs_assert (false);
+}
+
+void zs::io_thread_t::timer_event ()
+{
+    //  No timers here. This function is never called.
+    zs_assert (false);
+}
+
+void zs::io_thread_t::attach_session (session_t *session_)
+{
+    session_->set_index (sessions.size ());
+    sessions.push_back (session_); 
+}
+
+void zs::io_thread_t::detach_session (session_t *session_)
+{
+    //  O(1) removal of the session from the list.
+    sessions_t::size_type i = session_->get_index ();
+    sessions [i] = sessions [sessions.size () - 1];
+    sessions [i]->set_index (i);
+    sessions.pop_back ();
+}
+
+zs::i_poller *zs::io_thread_t::get_poller ()
+{
+    zs_assert (poller);
+    return poller;
+}
+
+void zs::io_thread_t::process_stop ()
+{
+    poller->rm_fd (signaler_handle);
+    poller->stop ();
+}
diff --git a/src/io_thread.hpp b/src/io_thread.hpp
new file mode 100644
index 0000000..a57aa34
--- /dev/null
+++ b/src/io_thread.hpp
@@ -0,0 +1,99 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_IO_THREAD_HPP_INCLUDED__
+#define __ZS_IO_THREAD_HPP_INCLUDED__
+
+#include <vector>
+
+#include "object.hpp"
+#include "i_thread.hpp"
+#include "i_poller.hpp"
+#include "i_poll_events.hpp"
+#include "fd_signaler.hpp"
+
+namespace zs
+{
+
+    //  Generic part of the I/O thread. Polling-mechanism-specific features
+    //  are implemented in separate "polling objects".
+
+    class io_thread_t : public object_t, public i_poll_events, public i_thread
+    {
+    public:
+
+        io_thread_t (class dispatcher_t *dispatcher_, int thread_slot_);
+
+        //  Launch the physical thread.
+        void start ();
+
+        //  Ask underlying thread to stop.
+        void stop ();
+
+        //  Wait till undelying thread terminates.
+        void join ();
+
+        //  To be called when the whole infrastrucure is being closed (zs_term).
+        //  It's vital to call the individual commands in this sequence:
+        //  stop, join, shutdown.
+        void shutdown ();
+
+        //  Returns signaler associated with this I/O thread.
+        i_signaler *get_signaler ();
+
+        //  i_poll_events implementation.
+        void in_event ();
+        void out_event ();
+        void timer_event ();
+
+        //  i_thread implementation.
+        void attach_session (class session_t *session_);
+        void detach_session (class session_t *session_);
+        struct i_poller *get_poller ();
+
+        //  Command handlers.
+        void process_stop ();
+
+        //  Returns load experienced by the I/O thread.
+        int get_load ();
+
+    private:
+
+        //  Clean-up.
+        ~io_thread_t ();
+
+        //  Poll thread gets notifications about incoming commands using
+        //  this signaler.
+        fd_signaler_t signaler;
+
+        //  Handle associated with signaler's file descriptor.
+        handle_t signaler_handle;
+
+        //  I/O multiplexing is performed using a poller object.
+        i_poller *poller;
+
+        //  Vector of all sessions associated with this app thread.
+        typedef std::vector <class session_t*> sessions_t;
+        sessions_t sessions;
+
+    };
+
+}
+
+#endif
diff --git a/src/ip.cpp b/src/ip.cpp
new file mode 100644
index 0000000..f435bef
--- /dev/null
+++ b/src/ip.cpp
@@ -0,0 +1,310 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdlib.h>
+#include <string>
+
+#include "ip.hpp"
+#include "platform.hpp"
+#include "err.hpp"
+#include "stdint.hpp"
+
+#if defined ZS_HAVE_SOLARIS
+
+#include <sys/sockio.h>
+#include <net/if.h>
+#include <unistd.h>
+
+//  On Solaris platform, network interface name can be queried by ioctl.
+static int resolve_nic_name (in_addr* addr_, char const *interface_)
+{
+    //  * resolves to INADDR_ANY
+    if (!interface_ || (strlen (interface_) == 1 && *interface_ == '*')) {
+        addr_->s_addr = htonl (INADDR_ANY);
+        return 0;
+    }
+
+    //  Create a socket.
+    int fd = socket (AF_INET, SOCK_DGRAM, 0);
+    zs_assert (fd != -1);
+
+    //  Retrieve number of interfaces.
+    lifnum ifn;
+    ifn.lifn_family = AF_UNSPEC;
+    ifn.lifn_flags = 0;
+    int rc = ioctl (fd, SIOCGLIFNUM, (char*) &ifn);
+    zs_assert (rc != -1);
+
+    //  Allocate memory to get interface names.
+    size_t ifr_size = sizeof (struct lifreq) * ifn.lifn_count;
+    char *ifr = (char*) malloc (ifr_size);
+    errno_assert (ifr);
+    
+    //  Retrieve interface names.
+    lifconf ifc;
+    ifc.lifc_family = AF_UNSPEC;
+    ifc.lifc_flags = 0;
+    ifc.lifc_len = ifr_size;
+    ifc.lifc_buf = ifr;
+    rc = ioctl (fd, SIOCGLIFCONF, (char*) &ifc);
+    zs_assert (rc != -1);
+
+    //  Find the interface with the specified name and AF_INET family.
+    bool found = false;
+    lifreq *ifrp = ifc.lifc_req;
+    for (int n = 0; n < (int) (ifc.lifc_len / sizeof (lifreq));
+          n ++, ifrp ++) {
+        if (!strcmp (interface_, ifrp->lifr_name)) {
+            rc = ioctl (fd, SIOCGLIFADDR, (char*) ifrp);
+            zs_assert (rc != -1);
+            if (ifrp->lifr_addr.ss_family == AF_INET) {
+                *addr_ = ((sockaddr_in*) &ifrp->lifr_addr)->sin_addr;
+                found = true;
+                break;
+            }
+        }
+    }
+
+    //  Clean-up.
+    free (ifr);
+    close (fd);
+
+    //  If interface was not found among interface names, we assume it's
+    //  specified in the form of IP address.
+    if (!found) {
+        rc = inet_pton (AF_INET, interface_, addr_);
+        if (rc != 1) {
+            errno = EINVAL;
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+#elif defined ZS_HAVE_AIX || ZS_HAVE_HPUX
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+
+#include "formatting.hpp"
+
+static int resolve_nic_name (in_addr* addr_, char const *interface_)
+{
+    //  * resolves to INADDR_ANY
+    if (!interface_ || (strlen (interface_) == 1 && *interface_ == '*')) {
+        addr_->s_addr = htonl (INADDR_ANY);
+        return 0;
+    }
+
+    //  Create a socket.
+    int sd = socket (AF_INET, SOCK_DGRAM, 0);
+    zs_assert (sd != -1);
+
+    struct ifreq ifr; 
+
+    //  Copy interface name for ioctl get.
+    zs_strncpy (ifr.ifr_name, interface_, sizeof (ifr.ifr_name));
+
+    //  Fetch interface address.
+    int rc = ioctl (sd, SIOCGIFADDR, (caddr_t) &ifr, sizeof (struct ifreq));
+
+    if(rc != -1) {
+        struct sockaddr *sa = (struct sockaddr *) &ifr.ifr_addr;
+        *addr_ = ((sockaddr_in*)sa)->sin_addr;
+    }
+    else {
+
+        //  Assume interface_ is in IP format xxx.xxx.xxx.xxx.
+        rc = inet_pton (AF_INET, interface_, addr_);
+        if (rc != 0) {
+            errno = EINVAL;
+            return -1;
+        }
+    }
+
+    //  Clean up.
+    close (sd);
+
+    return 0;
+}
+
+#elif defined ZS_HAVE_WINDOWS
+
+static int resolve_nic_name (in_addr* addr_, char const *interface_)
+{
+    //  * resolves to INADDR_ANY
+    if (!interface_ || (strlen (interface_) == 1 && *interface_ == '*')) {
+        addr_->s_addr = htonl (INADDR_ANY);
+        return 0;
+    }
+
+    //  Windows doesn't use sensible NIC names. Thus, we expect IP address of
+    //  the NIC instead.
+    in_addr addr;
+    ((sockaddr_in*) addr_)->sin_family = AF_INET;
+    addr.S_un.S_addr = inet_addr ((const char *) interface_);
+    if (addr.S_un.S_addr == INADDR_NONE) {
+        errno = EINVAL;
+        return -1;
+    }
+    *addr_ = addr;
+
+    return 0;
+}
+
+#elif ((defined ZS_HAVE_LINUX || defined ZS_HAVE_FREEBSD ||\
+    defined ZS_HAVE_OSX || defined ZS_HAVE_OPENBSD ||\
+    defined ZS_HAVE_QNXNTO) && defined ZS_HAVE_IFADDRS)
+
+#include <ifaddrs.h>
+
+//  On these platforms, network interface name can be queried
+//  using getifaddrs function.
+static int resolve_nic_name (in_addr* addr_, char const *interface_)
+{
+    //  * resolves to INADDR_ANY
+    if (!interface_ || (strlen (interface_) == 1 && *interface_ == '*')) {
+        addr_->s_addr = htonl (INADDR_ANY);
+        return 0;
+    }
+
+    //  Initialuse the output parameter.
+    memset (addr_, 0, sizeof (in_addr));
+
+    //  Get the addresses.
+    ifaddrs* ifa = NULL;
+    int rc = getifaddrs (&ifa);
+    zs_assert (rc == 0);    
+    zs_assert (ifa != NULL);
+
+    //  Find the corresponding network interface.
+    bool found = false;
+    for (ifaddrs *ifp = ifa; ifp != NULL ;ifp = ifp->ifa_next)
+        if (ifp->ifa_addr && ifp->ifa_addr->sa_family == AF_INET 
+            && !strcmp (interface_, ifp->ifa_name)) 
+        {
+            *addr_ = ((sockaddr_in*) ifp->ifa_addr)->sin_addr;
+            found = true;
+        }
+
+    //  Clean-up;
+    freeifaddrs (ifa);
+
+    //  If interface was not found among interface names, we assume it's
+    //  specified in the form of IP address.
+    if (!found) {
+        rc = inet_pton (AF_INET, interface_, addr_);
+        if (rc != 1) {
+            errno = EINVAL;
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+#else
+
+//  On other platforms interface name is interpreted as raw IP address.
+static int resolve_nic_name (in_addr* addr_, char const *interface_)
+{
+    //  * resolves to INADDR_ANY
+    if (!interface_ || (strlen (interface_) == 1 && *interface_ == '*')) {
+        addr_->s_addr = htonl (INADDR_ANY);
+        return 0;
+    }
+
+    //  Convert IP address into sockaddr_in structure.
+    int rc = inet_pton (AF_INET, interface_, addr_);
+    zs_assert (rc != 0);
+    errno_assert (rc == 1);
+
+    return 0;
+}
+
+#endif
+
+int zs::resolve_ip_interface (sockaddr_in* addr_, char const *interface_)
+{
+    //  Find the ':' that separates NIC name from port.
+    const char *delimiter = strchr (interface_, ':');
+    if (!delimiter) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    //  Clean the structure and fill in protocol family.
+    memset (addr_, 0, sizeof (sockaddr_in));
+    addr_->sin_family = AF_INET;
+
+    //  Resolve the name of the NIC.
+    std::string nic_name (interface_, delimiter - interface_);
+    if (resolve_nic_name (&addr_->sin_addr, nic_name.c_str ()) != 0)
+        return -1;
+
+    //  Resolve the port.
+    addr_->sin_port = htons ((uint16_t) atoi (delimiter + 1));
+    if (!addr_->sin_port) {
+        errno = EINVAL;
+        return 0;
+    }
+
+    return 0;
+}
+
+int zs::resolve_ip_hostname (sockaddr_in *addr_, const char *hostname_)
+{
+    //  Find the ':' that separates hostname name from port.
+    const char *delimiter = strchr (hostname_, ':');
+    if (!delimiter) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    //  Separate the hostname.
+    std::string hostname (hostname_, delimiter - hostname_);
+
+    //  Resolve host name.
+    addrinfo req;
+    memset (&req, 0, sizeof (req));
+    req.ai_family = AF_INET;
+    addrinfo *res;
+    int rc = getaddrinfo (hostname.c_str (), NULL, &req, &res);
+    if (rc) {
+        errno = EINVAL;
+        return -1;
+    }
+    zs_assert (res->ai_addr->sa_family == AF_INET);
+    memcpy (addr_, res->ai_addr, sizeof (sockaddr_in));
+    freeaddrinfo (res);
+    
+    //  Fill in the port number.
+    addr_->sin_port = htons ((uint16_t) atoi (delimiter + 1));
+    if (!addr_->sin_port) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/ip.hpp b/src/ip.hpp
new file mode 100644
index 0000000..90f02e3
--- /dev/null
+++ b/src/ip.hpp
@@ -0,0 +1,47 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_IP_HPP_INCLUDED__
+#define __ZS_IP_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#else
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#endif
+
+namespace zs
+{
+
+    //  Resolves network interface name in <nic-name>:<port> format. Symbol "*"
+    //  (asterisk) resolves to INADDR_ANY (all network interfaces).
+    int resolve_ip_interface (sockaddr_in* addr_, char const *interface_);
+
+    //  This function resolves a string in <hostname>:<port-number> format.
+    //  Hostname can be either the name of the host or its IP address.
+    int resolve_ip_hostname (sockaddr_in *addr_, const char *hostname_);
+}
+
+#endif 
diff --git a/src/kqueue.cpp b/src/kqueue.cpp
new file mode 100644
index 0000000..b0c23ee
--- /dev/null
+++ b/src/kqueue.cpp
@@ -0,0 +1,214 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_FREEBSD || defined ZS_HAVE_OPENBSD || defined ZS_HAVE_OSX
+
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/event.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <algorithm>
+
+#include "kqueue.hpp"
+#include "err.hpp"
+#include "config.hpp"
+#include "i_poll_events.hpp"
+
+zs::kqueue_t::kqueue_t ()
+{
+    //  Create event queue
+    kqueue_fd = kqueue ();
+    errno_assert (kqueue_fd != -1);
+}
+
+zs::kqueue_t::~kqueue_t ()
+{
+    close (kqueue_fd);
+}
+
+void zs::kqueue_t::kevent_add (fd_t fd_, short filter_, void *udata_)
+{
+    struct kevent ev;
+
+    EV_SET (&ev, fd_, filter_, EV_ADD, 0, 0, udata_);
+    int rc = kevent (kqueue_fd, &ev, 1, NULL, 0, NULL);
+    errno_assert (rc != -1);
+}
+
+void zs::kqueue_t::kevent_delete (fd_t fd_, short filter_)
+{
+    struct kevent ev;
+
+    EV_SET (&ev, fd_, filter_, EV_DELETE, 0, 0, NULL);
+    int rc = kevent (kqueue_fd, &ev, 1, NULL, 0, NULL);
+    errno_assert (rc != -1);
+}
+
+zs::handle_t zs::kqueue_t::add_fd (fd_t fd_, i_poll_events *reactor_)
+{
+    poll_entry_t *pe = new poll_entry_t;
+    zs_assert (pe != NULL);
+
+    pe->fd = fd_;
+    pe->flag_pollin = 0;
+    pe->flag_pollout = 0;
+    pe->reactor = reactor_;
+
+    handle_t handle;
+    handle.ptr = pe;
+    return handle;
+}
+
+void zs::kqueue_t::rm_fd (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    if (pe->flag_pollin)
+        kevent_delete (pe->fd, EVFILT_READ);
+    if (pe->flag_pollout)
+        kevent_delete (pe->fd, EVFILT_WRITE);
+    pe->fd = retired_fd;
+    retired.push_back (pe);
+}
+
+void zs::kqueue_t::set_pollin (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->flag_pollin = true;
+    kevent_add (pe->fd, EVFILT_READ, pe);
+}
+
+void zs::kqueue_t::reset_pollin (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->flag_pollin = false;
+    kevent_delete (pe->fd, EVFILT_READ);
+}
+
+void zs::kqueue_t::set_pollout (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->flag_pollout = true;
+    kevent_add (pe->fd, EVFILT_WRITE, pe);
+}
+
+void zs::kqueue_t::reset_pollout (handle_t handle_)
+{
+    poll_entry_t *pe = (poll_entry_t*) handle_.ptr;
+    pe->flag_pollout = false;
+    kevent_delete (pe->fd, EVFILT_WRITE);
+}
+
+void zs::kqueue_t::add_timer (i_poll_events *events_)
+{
+     timers.push_back (events_);
+}
+
+void zs::kqueue_t::cancel_timer (i_poll_events *events_)
+{
+    timers_t::iterator it = std::find (timers.begin (), timers.end (), events_);
+    if (it != timers.end ())
+        timers.erase (it);
+}
+
+int zs::kqueue_t::get_load ()
+{
+    return load.get ();
+}
+
+void zs::kqueue_t::start ()
+{
+    worker.start (worker_routine, this);
+}
+
+void zs::kqueue_t::stop ()
+{
+    stopping = true;
+}
+
+void zs::kqueue_t::join ()
+{
+    worker.stop ();
+}
+
+void zs::kqueue_t::loop ()
+{
+    while (!stopping) {
+
+        struct kevent ev_buf [max_io_events];
+
+        //  Compute time interval to wait.
+        timespec timeout = {max_timer_period / 1000,
+            (max_timer_period % 1000) * 1000000};
+
+        //  Wait for events.
+        int n = kevent (kqueue_fd, NULL, 0,
+             &ev_buf [0], max_io_events, timers.empty () ? NULL : &timeout);
+        if (n == -1 && errno == EINTR)
+            continue;
+        errno_assert (n != -1);
+
+        //  Handle timer.
+        if (!n) {
+
+            //  Use local list of timers as timer handlers may fill new timers
+            //  into the original array.
+            timers_t t;
+            std::swap (timers, t);
+
+            //  Trigger all the timers.
+            for (timers_t::iterator it = t.begin (); it != t.end (); it ++)
+                (*it)->timer_event ();
+
+            continue;
+        }
+
+        for (int i = 0; i < n; i ++) {
+            poll_entry_t *pe = (poll_entry_t*) ev_buf [i].udata;
+
+            if (pe->fd == retired_fd)
+                continue;
+            if (ev_buf [i].flags & EV_EOF)
+                pe->reactor->in_event ();
+            if (pe->fd == retired_fd)
+                continue;
+            if (ev_buf [i].filter == EVFILT_WRITE)
+                pe->reactor->out_event ();
+            if (pe->fd == retired_fd)
+                continue;
+            if (ev_buf [i].filter == EVFILT_READ)
+                pe->reactor->in_event ();
+        }
+
+        //  Destroy retired event sources.
+        for (retired_t::iterator it = retired.begin (); it != retired.end ();
+              it ++)
+            delete *it;
+        retired.clear ();
+    }
+}
+
+void zs::kqueue_t::worker_routine (void *arg_)
+{
+    ((kqueue_t*) arg_)->loop ();
+}
+
+#endif
diff --git a/src/kqueue.hpp b/src/kqueue.hpp
new file mode 100644
index 0000000..f060b28
--- /dev/null
+++ b/src/kqueue.hpp
@@ -0,0 +1,112 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_KQUEUE_HPP_INCLUDED__
+#define __ZS_KQUEUE_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_FREEBSD || defined ZS_HAVE_OPENBSD || defined ZS_HAVE_OSX
+
+#include <vector>
+
+#include "i_poller.hpp"
+#include "fd.hpp"
+#include "thread.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  Implements socket polling mechanism using the BSD-specific
+    //  kqueue interface.
+
+    class kqueue_t : public i_poller
+    {
+    public:
+
+        kqueue_t ();
+        virtual ~kqueue_t ();
+
+        //  i_poller implementation.
+        handle_t add_fd (fd_t fd_, i_poll_events *events_);
+        void rm_fd (handle_t handle_);
+        void set_pollin (handle_t handle_);
+        void reset_pollin (handle_t handle_);
+        void set_pollout (handle_t handle_);
+        void reset_pollout (handle_t handle_);
+        void add_timer (i_poll_events *events_);
+        void cancel_timer (i_poll_events *events_);
+        int get_load ();
+        void start ();
+        void stop ();
+        void join ();
+
+    private:
+
+        //  Main worker thread routine.
+        static void worker_routine (void *arg_);
+
+        //  Main event loop.
+        void loop ();
+
+        //  File descriptor referring to the kernel event queue.
+        fd_t kqueue_fd;
+
+        //  Adds the event to the kqueue.
+        void kevent_add (fd_t fd_, short filter_, void *udata_);
+
+        //  Deletes the event from the kqueue.
+        void kevent_delete (fd_t fd_, short filter_);
+
+        struct poll_entry_t
+        {
+            fd_t fd;
+            bool flag_pollin;
+            bool flag_pollout;
+            i_poll_events *reactor;
+        };
+
+        //  List of retired event sources.
+        typedef std::vector <poll_entry_t*> retired_t;
+        retired_t retired;
+
+        //  List of all the engines waiting for the timer event.
+        typedef std::vector <struct i_poll_events*> timers_t;
+        timers_t timers;
+
+        //  If true, thread is in the process of shutting down.
+        bool stopping;
+
+        //  Handle of the physical thread doing the I/O work.
+        thread_t worker;
+
+        //  Load of the poller. Currently number of file descriptors
+        //  registered with the poller.
+        atomic_counter_t load;
+
+        kqueue_t (const kqueue_t&);
+        void operator = (const kqueue_t&);
+    };
+
+}
+
+#endif
+
+#endif
diff --git a/src/listener.cpp b/src/listener.cpp
new file mode 100644
index 0000000..ae4a80f
--- /dev/null
+++ b/src/listener.cpp
@@ -0,0 +1,170 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "listener.hpp"
+#include "simple_semaphore.hpp"
+#include "zmq_tcp_engine.hpp"
+#include "io_thread.hpp"
+#include "session_stub.hpp"
+#include "session.hpp"
+#include "err.hpp"
+#include "dummy_aggregator.hpp"
+#include "dummy_distributor.hpp"
+
+zs::listener_t::listener_t (io_thread_t *thread_, const char *addr_,
+      session_t *peer_, bool has_in_, bool has_out_, uint64_t taskset_) :
+    io_object_t (thread_),
+    poller (NULL),
+    addr (addr_),
+    peer (peer_),
+    taskset (taskset_),
+    has_in (has_in_),
+    has_out (has_out_)
+{
+}
+
+void zs::listener_t::terminate ()
+{
+    for (session_stubs_t::size_type i = 0; i != session_stubs.size (); i++)
+        session_stubs [i]->terminate ();
+    delete this;
+}
+
+void zs::listener_t::shutdown ()
+{
+    for (session_stubs_t::size_type i = 0; i != session_stubs.size (); i++)
+        session_stubs [i]->shutdown ();
+    delete this;
+}
+
+zs::listener_t::~listener_t ()
+{
+}
+
+void zs::listener_t::got_identity (session_stub_t *session_stub_,
+    const char *identity_)
+{
+    //  Get the engine allready disconnected from the stub and poller.
+    i_engine *engine = session_stub_->detach_engine ();
+    zs_assert (engine);
+
+    //  Find the corresponding session.
+    session_t *session;
+    sessions_t::iterator it = sessions.find (identity_);
+
+    //  Destroy the stub.
+    int i = session_stub_->get_index ();
+    session_stubs [i] = session_stubs [session_stubs.size () - 1];
+    session_stubs [i]->set_index (i);
+    session_stubs.pop_back ();
+    session_stub_->terminate ();
+
+    //  If there's no session with the specified identity, create one.
+    if (it != sessions.end ()) {
+        session = it->second;
+        session->inc_seqnum ();
+    }
+    else {
+
+        //  Choose an I/O thread with the least load to handle the new session.
+        io_thread_t *io_thread = choose_io_thread (taskset);
+
+        //  Create the session and bind it to the I/O thread and peer. Make
+        //  sure that the peer session won't get deallocated till it processes
+        //  the subsequent bind command.
+        i_mux *mux = new dummy_aggregator_t;
+        zs_assert (mux);
+        i_demux *demux = new dummy_distributor_t;
+        zs_assert (demux);
+        session = new session_t (io_thread, io_thread, mux, demux, false, true);
+        zs_assert (session);
+        session->inc_seqnum ();
+        session->inc_seqnum ();
+        peer->inc_seqnum ();
+        send_reg_and_bind (session, peer, has_in, has_out);
+    }
+
+    //  Attach the engine to the session.
+    send_engine (session, engine);
+}
+
+void zs::listener_t::process_reg (simple_semaphore_t *smph_)
+{
+    zs_assert (!poller);
+    poller = get_poller ();
+
+    //  Open the listening socket.
+    int rc = tcp_listener.open (addr.c_str ());
+    zs_assert (rc == 0);
+
+    //  Unlock the application thread that created the listener.
+    if (smph_)
+        smph_->post ();
+
+    //  Start polling for incoming connections.
+    handle = poller->add_fd (tcp_listener.get_fd (), this);
+    poller->set_pollin (handle);
+}
+
+void zs::listener_t::process_unreg (simple_semaphore_t *smph_)
+{
+    //  Disassociate listener from the poller.
+    zs_assert (poller);
+    poller->rm_fd (handle);
+    poller = NULL;
+
+    //  Unlock the application thread closing the listener.
+    if (smph_)
+        smph_->post ();
+}
+
+void zs::listener_t::in_event ()
+{
+    fd_t fd = tcp_listener.accept ();
+
+    //  If connection was reset by the peer in the meantime, just ignore it.
+    //  TODO: Handle specific errors like ENFILE/EMFILE etc.
+    if (fd == retired_fd)
+        return;
+
+    //  Create an session stub for the engine to take care for it till its
+    //  identity is retreived.
+    session_stub_t *session_stub = new session_stub_t (this);
+    zs_assert (session_stub);
+    session_stub->set_index (session_stubs.size ());
+    session_stubs.push_back (session_stub);
+
+    //  Create an engine to encaspulate the socket. Engine will register itself
+    //  with the stub so the stub will be able to free it in case of shutdown.
+    zmq_tcp_engine_t *engine = new zmq_tcp_engine_t (fd);
+    zs_assert (engine);
+    engine->attach (poller, session_stub);
+}
+
+void zs::listener_t::out_event ()
+{
+    zs_assert (false);
+}
+
+void zs::listener_t::timer_event ()
+{
+    zs_assert (false);
+}
+
+
diff --git a/src/listener.hpp b/src/listener.hpp
new file mode 100644
index 0000000..f3c745a
--- /dev/null
+++ b/src/listener.hpp
@@ -0,0 +1,110 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_LISTENER_HPP_INCLUDED__
+#define __ZS_LISTENER_HPP_INCLUDED__
+
+#include <map>
+#include <vector>
+#include <string>
+
+#include "io_object.hpp"
+#include "tcp_listener.hpp"
+#include "i_poller.hpp"
+#include "i_poll_events.hpp"
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    class listener_t : public io_object_t, public i_poll_events
+    {
+    public:
+
+        listener_t (class io_thread_t *thread_, const char *addr_,
+            class session_t *peer_, bool has_in_, bool has_out_,
+            uint64_t taskset_);
+
+        void terminate ();
+        void shutdown ();
+
+        //  This function is called by session stub once the identity
+        //  is retrieved from the incoming connection.
+        void got_identity (class session_stub_t *session_stub_,
+            const char *identity_);
+
+        void process_reg (class simple_semaphore_t *smph_);
+        void process_unreg (class simple_semaphore_t *smph_);
+
+        //  i_poll_events implementation.
+        void in_event ();
+        void out_event ();
+        void timer_event ();
+
+    private:
+
+        ~listener_t ();
+
+        struct i_poller *poller;
+
+        //  Handle corresponding to the listening socket.
+        handle_t handle;
+
+        //  Actual listening socket.
+        tcp_listener_t tcp_listener;
+
+        //  Address to bind to.
+        std::string addr;
+
+        //  Peer session. All the newly created connections should bind to
+        //  this session.
+        session_t *peer;
+
+        //  Taskset specifies which I/O threads are to be use to handle
+        //  newly created connections (0 = all).
+        uint64_t taskset;
+
+        //  Sessions created by this listener are stored in this map. They are
+        //  indexed by peer identities so that the same peer connects to the
+        //  same session after reconnection.
+        //  NB: Sessions are destroyed from other place and possibly later on,
+        //  so no need to care about them during listener object termination.
+        typedef std::map <std::string, class session_t*> sessions_t;
+        sessions_t sessions;
+
+        //  List of engines (bound to temorary session stubs) that we haven't
+        //  retrieved the identity from so far.
+        typedef std::vector <class session_stub_t*> session_stubs_t;
+        session_stubs_t session_stubs;
+
+        //  If true, create inbound pipe when binding new connection
+        //  to the peer.
+        bool has_in;
+
+        //  If true, create outbound pipe when binding new connection
+        //  to the peer.
+        bool has_out;      
+
+        listener_t (const listener_t&);
+        void operator = (const listener_t&);
+    };
+
+}
+
+#endif
diff --git a/src/load_balancer.cpp b/src/load_balancer.cpp
new file mode 100644
index 0000000..63dc15c
--- /dev/null
+++ b/src/load_balancer.cpp
@@ -0,0 +1,130 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "load_balancer.hpp"
+#include "pipe_writer.hpp"
+#include "err.hpp"
+#include "session.hpp"
+#include "msg.hpp"
+
+zs::load_balancer_t::load_balancer_t () :
+    session (NULL),
+    current (0)
+{
+}
+
+void zs::load_balancer_t::set_session (session_t *session_)
+{
+    zs_assert (!session);
+    session = session_;
+}
+
+void zs::load_balancer_t::shutdown ()
+{
+    //  No need to deallocate pipes here. They'll be deallocated during the
+    //  shutdown of the dispatcher.
+    delete this;
+}
+
+void zs::load_balancer_t::terminate ()
+{
+    //  Pipe unregisters itself during the call to terminate, so the pipes
+    //  list shinks by one in each iteration.
+    while (!pipes.empty ())
+        pipes [0]->terminate ();
+
+   delete this;
+}
+
+zs::load_balancer_t::~load_balancer_t ()
+{
+}
+
+void zs::load_balancer_t::attach_pipe (pipe_writer_t *pipe_)
+{
+    //  Associate demux with a new pipe.
+    pipe_->set_demux (this);
+    pipe_->set_index (pipes.size ());
+    pipes.push_back (pipe_);
+}
+
+void zs::load_balancer_t::detach_pipe (pipe_writer_t *pipe_)
+{
+    //  Release the reference to the pipe.
+    int index = pipe_->get_index ();
+    pipe_->set_index (-1);
+    pipes [index] = pipes.back ();
+    pipes [index]->set_index (index);
+    pipes.pop_back ();
+}
+
+bool zs::load_balancer_t::empty ()
+{
+    return pipes.empty ();
+}
+
+bool zs::load_balancer_t::send (zs_msg *msg_)
+{
+    //  If there are no pipes, message cannot be sent.
+    if (pipes.size () == 0)
+        return false;
+
+    //  Find the first pipe that is ready to accept the message.
+    bool found = false;
+    for (pipes_t::size_type i = 0; !found && i < pipes.size (); i++) {
+//        if (pipes [current]->check_write (msg))
+            found = true;
+//        else
+//            current = (current + 1) % pipes.size ();
+    }
+
+    //  Oops, no pipe is ready to accept the message.
+    if (!found)
+        return false;
+
+    //  Send the message to the selected pipe.
+    write_to_pipe (pipes [current], msg_);
+    current = (current + 1) % pipes.size ();
+
+    //  Detach the original message from the data buffer.
+    zs_msg_init (msg_);
+
+    return true;
+}
+
+void zs::load_balancer_t::flush ()
+{
+    //  Flush all pipes. If there's large number of pipes, it can be pretty
+    //  inefficient (especially if there's new message only in a single pipe).
+    //  Can it be improved?
+    for (pipes_t::iterator it = pipes.begin (); it != pipes.end (); it ++)
+        (*it)->flush ();
+}
+
+void zs::load_balancer_t::write_to_pipe (class pipe_writer_t *pipe_,
+    struct zs_msg *msg_)
+{
+    if (!pipe_->write (msg_)) {
+        //  TODO: Push gap notification to the pipe.
+        zs_assert (false);
+    }
+}
+
diff --git a/src/load_balancer.hpp b/src/load_balancer.hpp
new file mode 100644
index 0000000..9cdc68f
--- /dev/null
+++ b/src/load_balancer.hpp
@@ -0,0 +1,73 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_LOAD_BALANCER_HPP_INCLUDED__
+#define __ZS_LOAD_BALANCER_HPP_INCLUDED__
+
+#include <vector>
+
+#include <i_demux.hpp>
+
+namespace zs
+{
+
+    //  Object to distribute messages to outbound pipes.
+
+    class load_balancer_t : public i_demux
+    {
+    public:
+
+        load_balancer_t ();
+
+        //  i_demux implementation.
+        void set_session (class session_t *session_);
+        void shutdown ();
+        void terminate ();
+        void attach_pipe (class pipe_writer_t *pipe_);
+        void detach_pipe (class pipe_writer_t *pipe_);
+        bool empty ();
+        bool send (struct zs_msg *msg_);
+        void flush ();
+
+    private:
+
+        //  Clean-up.
+        ~load_balancer_t ();
+
+        //  Reference to the owner session object.
+        class session_t *session;
+
+        //  Writes the message to the pipe if possible. If it isn't, writes
+        //  a gap notification to the pipe.
+        void write_to_pipe (class pipe_writer_t *pipe_, struct zs_msg *msg_);
+
+        //  The list of outbound pipes.
+        typedef std::vector <class pipe_writer_t*> pipes_t;
+        pipes_t pipes;
+
+        //  Current pipe to write next message to.
+        pipes_t::size_type current;
+
+        load_balancer_t (const load_balancer_t&);
+        void operator = (const load_balancer_t&);
+    };
+
+}
+
+#endif
diff --git a/src/msg.hpp b/src/msg.hpp
new file mode 100644
index 0000000..f4f4d26
--- /dev/null
+++ b/src/msg.hpp
@@ -0,0 +1,49 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_MSG_HPP_INCLUDE__
+#define __ZS_MSG_HPP_INCLUDE__
+
+#include <stddef.h>
+
+#include "../include/zs.h"
+
+#include "atomic_counter.hpp"
+
+//namespace zs
+//{
+
+    //  Shared message buffer. Message data are either allocated in one
+    //  continguous block along with this structure - thus avoiding one
+    //  malloc/free pair or they are stored in used-supplied memory.
+    //  In the latter case, ffn member stores pointer to the function to be
+    //  used to deallocate the data. If the buffer is actually shared (there
+    //  are at least 2 references to it) refcount member contains number of
+    //  references.
+    struct zs_msg_content
+    {
+        void *data;
+        size_t size;
+        zs_free_fn *ffn;
+        zs::atomic_counter_t refcnt;
+    };
+
+//}
+
+#endif
diff --git a/src/mutex.hpp b/src/mutex.hpp
new file mode 100644
index 0000000..a7f95da
--- /dev/null
+++ b/src/mutex.hpp
@@ -0,0 +1,116 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_MUTEX_HPP_INCLUDED__
+#define __ZS_MUTEX_HPP_INCLUDED__
+
+#include "platform.hpp"
+#include "err.hpp"
+
+//  Mutex class encapsulates OS mutex in a platform-independent way.
+
+#ifdef ZS_HAVE_WINDOWS
+
+#include "windows.hpp"
+
+namespace zs
+{
+
+    class mutex_t
+    {
+    public:
+        inline mutex_t ()
+        {
+            InitializeCriticalSection (&cs);
+        }
+
+        inline ~mutex_t ()
+        {
+            DeleteCriticalSection (&cs);
+        }
+
+        inline void lock ()
+        {
+            EnterCriticalSection (&cs);
+        }
+
+        inline void unlock ()
+        {
+            LeaveCriticalSection (&cs);
+        }
+
+    private:
+
+        CRITICAL_SECTION cs;
+
+        //  Disable copy construction and assignment.
+        mutex_t (const mutex_t&);
+        void operator = (const mutex_t&);
+    };
+
+}
+
+#else
+
+#include <pthread.h>
+
+namespace zs
+{
+
+    class mutex_t
+    {
+    public:
+        inline mutex_t ()
+        {
+            int rc = pthread_mutex_init (&mutex, NULL);
+            errno_assert (rc == 0);
+        }
+
+        inline ~mutex_t ()
+        {
+            int rc = pthread_mutex_destroy (&mutex);
+            errno_assert (rc == 0);
+        }
+
+        inline void lock ()
+        {
+            int rc = pthread_mutex_lock (&mutex);
+            errno_assert (rc == 0);
+        }
+
+        inline void unlock ()
+        {
+            int rc = pthread_mutex_unlock (&mutex);
+            errno_assert (rc == 0);
+        }
+
+    private:
+
+        pthread_mutex_t mutex;
+
+        //  Disable copy construction and assignment.
+        mutex_t (const mutex_t&);
+        void operator = (const mutex_t&);
+    };
+
+}
+
+#endif
+
+#endif
diff --git a/src/object.cpp b/src/object.cpp
new file mode 100644
index 0000000..8a154ae
--- /dev/null
+++ b/src/object.cpp
@@ -0,0 +1,294 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "object.hpp"
+#include "dispatcher.hpp"
+#include "err.hpp"
+#include "pipe_reader.hpp"
+#include "pipe_writer.hpp"
+#include "session.hpp"
+#include "io_thread.hpp"
+#include "simple_semaphore.hpp"
+#include "i_engine.hpp"
+
+zs::object_t::object_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    dispatcher (dispatcher_),
+    thread_slot (thread_slot_)
+{
+}
+
+zs::object_t::object_t (object_t *parent_) :
+    dispatcher (parent_->dispatcher),
+    thread_slot (parent_->thread_slot)
+{
+}
+
+zs::object_t::~object_t ()
+{
+}
+
+int zs::object_t::thread_slot_count ()
+{
+    return dispatcher->thread_slot_count ();
+}
+
+int zs::object_t::get_thread_slot ()
+{
+    return thread_slot;
+}
+
+void zs::object_t::process_command (command_t &cmd_)
+{
+    switch (cmd_.type) {
+
+    case command_t::head:
+        process_head (cmd_.args.head.bytes);
+        break;
+
+    case command_t::tail:
+        process_tail (cmd_.args.tail.bytes);
+        break;
+
+    case command_t::engine:
+        process_engine (cmd_.args.engine.engine);
+        break;
+
+    case command_t::bind:
+        process_bind (cmd_.args.bind.reader, cmd_.args.bind.peer);
+        break;
+
+    case command_t::reg:
+        process_reg (cmd_.args.reg.smph);
+        break;
+
+    case command_t::reg_and_bind:
+        process_reg_and_bind (cmd_.args.reg_and_bind.peer,
+            cmd_.args.reg_and_bind.flow_in, cmd_.args.reg_and_bind.flow_out);
+        break;
+
+    case command_t::unreg:
+        process_unreg (cmd_.args.unreg.smph);
+        break;
+
+    case command_t::terminate:
+        process_terminate ();
+        break;
+
+    case command_t::terminate_ack:
+        process_terminate_ack ();
+        break;
+
+    case command_t::stop:
+        process_stop ();
+        return;
+
+    default:
+        zs_assert (false);
+    }
+}
+
+void zs::object_t::create_pipe (object_t *reader_parent_,
+    object_t *writer_parent_, uint64_t hwm_, uint64_t lwm_,
+    pipe_reader_t **reader_, pipe_writer_t **writer_)
+{
+    dispatcher->create_pipe (reader_parent_, writer_parent_, hwm_, lwm_,
+        reader_, writer_);
+}
+
+void zs::object_t::destroy_pipe (pipe_t *pipe_)
+{
+    dispatcher->destroy_pipe (pipe_);
+}
+
+int zs::object_t::register_inproc_endpoint (const char *endpoint_,
+    session_t *session_)
+{
+    return dispatcher->register_inproc_endpoint (endpoint_, session_);
+}
+
+zs::object_t *zs::object_t::get_inproc_endpoint (const char *endpoint_)
+{
+    return dispatcher->get_inproc_endpoint (endpoint_);
+}
+
+void zs::object_t::unregister_inproc_endpoints (session_t *session_)
+{
+    dispatcher->unregister_inproc_endpoints (session_);
+}
+
+zs::io_thread_t *zs::object_t::choose_io_thread (uint64_t taskset_)
+{
+    return dispatcher->choose_io_thread (taskset_);
+}
+
+void zs::object_t::send_stop ()
+{
+    //  Send command goes always to the current object. To-self pipe is
+    //  used exclusively for sending this command.
+    command_t cmd;
+    cmd.destination = this;
+    cmd.type = command_t::stop;
+    dispatcher->write (thread_slot, thread_slot, cmd);
+}
+
+void zs::object_t::send_bind (object_t *destination_, pipe_reader_t *reader_,
+    session_t *peer_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::bind;
+    cmd.args.bind.reader = reader_;
+    cmd.args.bind.peer = peer_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_head (object_t *destination_, uint64_t bytes_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::head;
+    cmd.args.head.bytes = bytes_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_tail (object_t *destination_, uint64_t bytes_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::tail;
+    cmd.args.tail.bytes = bytes_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_reg (object_t *destination_, simple_semaphore_t *smph_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::reg;
+    cmd.args.reg.smph = smph_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_reg_and_bind (object_t *destination_,
+    session_t *peer_, bool flow_in_, bool flow_out_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::reg_and_bind;
+    cmd.args.reg_and_bind.peer = peer_;
+    cmd.args.reg_and_bind.flow_in = flow_in_;
+    cmd.args.reg_and_bind.flow_out = flow_out_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_unreg (object_t *destination_,
+    simple_semaphore_t *smph_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::unreg;
+    cmd.args.unreg.smph = smph_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_engine (object_t *destination_, i_engine *engine_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::engine;
+    cmd.args.engine.engine = engine_;
+    send_command (cmd);
+}
+
+void zs::object_t::send_terminate (object_t *destination_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::terminate;
+    send_command (cmd);
+}
+
+void zs::object_t::send_terminate_ack (object_t *destination_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::terminate_ack;
+    send_command (cmd);
+}
+
+void zs::object_t::process_stop ()
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_bind (pipe_reader_t *reader_, session_t *peer_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_head (uint64_t bytes_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_tail (uint64_t bytes_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_reg (simple_semaphore_t *smph_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_reg_and_bind (session_t *session_,
+    bool flow_in_, bool flow_out_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_unreg (simple_semaphore_t *smph_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_engine (i_engine *engine_)
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_terminate ()
+{
+    zs_assert (false);
+}
+
+void zs::object_t::process_terminate_ack ()
+{
+    zs_assert (false);
+}
+
+void zs::object_t::send_command (command_t &cmd_)
+{
+    int destination_thread_slot = cmd_.destination->get_thread_slot ();
+    if (destination_thread_slot == thread_slot)
+        cmd_.destination->process_command (cmd_);
+    else 
+        dispatcher->write (thread_slot, destination_thread_slot, cmd_);
+}
+
diff --git a/src/object.hpp b/src/object.hpp
new file mode 100644
index 0000000..a4f93ae
--- /dev/null
+++ b/src/object.hpp
@@ -0,0 +1,105 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_OBJECT_HPP_INCLUDED__
+#define __ZS_OBJECT_HPP_INCLUDED__
+
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    //  Base class for all objects that participate in inter-thread
+    //  communication.
+
+    class object_t
+    {
+    public:
+
+        object_t (class dispatcher_t *dispatcher_, int thread_slot_);
+        object_t (object_t *parent_);
+        ~object_t ();
+
+        int get_thread_slot ();
+        void process_command (struct command_t &cmd_);
+
+    protected:
+
+        //  Derived object can use following functions to interact with
+        //  global repositories. See dispatcher.hpp for function details.
+        int thread_slot_count ();
+        void create_pipe (class object_t *reader_parent_,
+            class object_t *writer_parent_, uint64_t hwm_, uint64_t lwm_,
+            class pipe_reader_t **reader_, class pipe_writer_t **writer_);
+        void destroy_pipe (class pipe_t *pipe_);
+        int register_inproc_endpoint (const char *endpoint_,
+            class session_t *session_);
+        class object_t *get_inproc_endpoint (const char *endpoint_);
+        void unregister_inproc_endpoints (class session_t *session_);
+        class io_thread_t *choose_io_thread (uint64_t taskset_);
+
+        //  Derived object can use these functions to send commands
+        //  to other objects.
+        void send_stop ();
+        void send_bind (object_t *destination_, class pipe_reader_t *reader_,
+            class session_t *peer_);
+        void send_head (object_t *destination_, uint64_t bytes_);
+        void send_tail (object_t *destination_, uint64_t bytes_);
+        void send_reg (object_t *destination_,
+            class simple_semaphore_t *smph_);
+        void send_reg_and_bind (object_t *destination_, class session_t *peer_,
+            bool flow_in_, bool flow_out_);
+        void send_unreg (object_t *destination_,
+            class simple_semaphore_t *smph_);
+        void send_engine (object_t *destination_, struct i_engine *engine_);
+        void send_terminate (object_t *destination_);
+        void send_terminate_ack (object_t *destination_);
+
+        //  These handlers can be overloaded by the derived objects. They are
+        //  called when command arrives from another thread.
+        virtual void process_stop ();
+        virtual void process_bind (class pipe_reader_t *reader_,
+            class session_t *peer_);
+        virtual void process_head (uint64_t bytes_);
+        virtual void process_tail (uint64_t bytes_);
+        virtual void process_reg (class simple_semaphore_t *smph_);
+        virtual void process_reg_and_bind (class session_t *peer_,
+            bool flow_in_, bool flow_out_);
+        virtual void process_unreg (class simple_semaphore_t *smph_);
+        virtual void process_engine (struct i_engine *engine_);
+        virtual void process_terminate ();
+        virtual void process_terminate_ack ();
+
+        //  Pointer to the root of the infrastructure.
+        class dispatcher_t *dispatcher;
+
+        //  Slot ID of the thread the object belongs to.
+        int thread_slot;
+
+    private:
+
+        void send_command (command_t &cmd_);
+
+        object_t (const object_t&);
+        void operator = (const object_t&);
+    };
+
+}
+
+#endif
diff --git a/src/p2p.cpp b/src/p2p.cpp
new file mode 100644
index 0000000..f15b663
--- /dev/null
+++ b/src/p2p.cpp
@@ -0,0 +1,29 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "p2p.hpp"
+#include "app_thread.hpp"
+#include "session.hpp"
+
+zs::p2p_t::p2p_t (app_thread_t *thread_, session_t *session_) :
+    socket_base_t (thread_, session_)
+{
+}
diff --git a/src/p2p.hpp b/src/p2p.hpp
new file mode 100644
index 0000000..1032a61
--- /dev/null
+++ b/src/p2p.hpp
@@ -0,0 +1,42 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_P2P_HPP_INCLUDED__
+#define __ZS_P2P_HPP_INCLUDED__
+
+#include "socket_base.hpp"
+
+namespace zs
+{
+
+    class p2p_t : public socket_base_t
+    {
+    public:
+
+        p2p_t (class app_thread_t *thread_, class session_t *session_);
+
+    private:
+
+        p2p_t (const p2p_t&);
+        void operator = (const p2p_t&);
+    };
+
+}
+
+#endif
diff --git a/src/pipe.cpp b/src/pipe.cpp
new file mode 100644
index 0000000..26042ae
--- /dev/null
+++ b/src/pipe.cpp
@@ -0,0 +1,47 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "pipe.hpp"
+
+zs::pipe_t::pipe_t () :
+    ypipe_t <zs_msg, false, message_pipe_granularity> (false),
+    index (-1)
+{
+}
+
+zs::pipe_t::~pipe_t ()
+{
+    //  Flush any outstanding messages to the pipe.
+    flush ();
+
+    //  Deallocate all the messages in the pipe.
+    zs_msg msg;
+    while (read (&msg))
+        zs_msg_close (&msg);
+}
+
+void zs::pipe_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zs::pipe_t::get_index ()
+{
+    return index;
+}
diff --git a/src/pipe.hpp b/src/pipe.hpp
new file mode 100644
index 0000000..c0e722d
--- /dev/null
+++ b/src/pipe.hpp
@@ -0,0 +1,57 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_PIPE_HPP_INCLUDED__
+#define __ZS_PIPE_HPP_INCLUDED__
+
+#include "../include/zs.h"
+
+#include "ypipe.hpp"
+#include "config.hpp"
+
+namespace zs
+{
+
+    //  Message pipe. A simple wrapper on top of ypipe.
+
+    class pipe_t : public ypipe_t <zs_msg, false, message_pipe_granularity>
+    {
+        //  Dispatcher is a friend so that it can create & destroy the pipes.
+        //  By making constructor & destructor private we are sure that nobody
+        //  except dispatcher messes with pipes.
+        friend class dispatcher_t;
+
+    private:
+
+        pipe_t ();
+        ~pipe_t ();
+
+        void set_index (int index_);
+        int get_index ();
+
+        //  Index of the pipe in dispatcher's array of pipes.
+        int index;
+
+        pipe_t (const pipe_t&);
+        void operator = (const pipe_t&);
+    }; 
+
+}
+
+#endif
diff --git a/src/pipe_reader.cpp b/src/pipe_reader.cpp
new file mode 100644
index 0000000..5585b92
--- /dev/null
+++ b/src/pipe_reader.cpp
@@ -0,0 +1,118 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "pipe_reader.hpp"
+#include "pipe.hpp"
+#include "err.hpp"
+#include "i_mux.hpp"
+
+zs::pipe_reader_t::pipe_reader_t (object_t *parent_, pipe_t *pipe_,
+      uint64_t hwm_, uint64_t lwm_) :
+    object_t (parent_),
+    pipe (pipe_),
+    peer (NULL),
+    mux (NULL),
+    index (-1),
+    hwm (hwm_),
+    lwm (lwm_),
+    head (0),
+    tail (0),
+    last_sent_head (0)
+{
+}
+
+void zs::pipe_reader_t::set_peer (object_t *peer_)
+{
+    peer = peer_;
+}
+
+zs::pipe_reader_t::~pipe_reader_t ()
+{
+}
+
+void zs::pipe_reader_t::set_mux (i_mux *mux_)
+{
+    mux = mux_;
+}
+
+void zs::pipe_reader_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zs::pipe_reader_t::get_index ()
+{
+    return index;
+}
+
+void zs::pipe_reader_t::process_tail (uint64_t bytes_)
+{
+    tail = bytes_;
+    mux->reactivate (this);
+}
+
+bool zs::pipe_reader_t::read (struct zs_msg *msg_)
+{
+    //  Read a message.
+    if (!pipe->read (msg_)) {
+        mux->deactivate (this);
+        return false;
+    }
+
+    //  If successfull, adjust the head of the pipe.
+    head += zs_msg_size (msg_);
+
+    //  If pipe writer wasn't notified about the head position for long enough,
+    //  notify it.
+    if (head - last_sent_head >= hwm - lwm) {
+        send_head (peer, head);
+        last_sent_head = head;
+    }
+
+    if (zs_msg_type (msg_) == ZS_DELIMITER) {
+
+        //  Detach the pipe from the mux and send termination request to
+        //  the pipe writer.
+        mux->detach_pipe (this);
+        mux = NULL;
+        send_terminate (peer);
+        return false;
+    }
+
+    return true;
+}
+
+void zs::pipe_reader_t::terminate ()
+{
+    //  Detach the pipe from the mux and send termination request to
+    //  the pipe writer.
+    if (mux) {
+        mux->detach_pipe (this);
+        mux = NULL;
+    }
+    send_terminate (peer);
+}
+
+void zs::pipe_reader_t::process_terminate_ack ()
+{
+    //  Ask dispatcher to deallocate the pipe.
+    destroy_pipe (pipe);
+}
diff --git a/src/pipe_reader.hpp b/src/pipe_reader.hpp
new file mode 100644
index 0000000..bc3fd2e
--- /dev/null
+++ b/src/pipe_reader.hpp
@@ -0,0 +1,89 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_PIPE_READER_HPP_INCLUDED__
+#define __ZS_PIPE_READER_HPP_INCLUDED__
+
+#include "object.hpp"
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    class pipe_reader_t : public object_t
+    {
+        //  Dispatcher is a friend so that it can create & destroy the reader.
+        //  By making constructor & destructor private we are sure that nobody
+        //  except dispatcher messes with readers.
+        friend class dispatcher_t;
+
+    public:
+
+        //  Set & get index in the associated mux object.
+        void set_mux (struct i_mux *mux_);
+        void set_index (int index_);
+        int get_index ();
+
+        //  Reads a message to the underlying pipe.
+        bool read (struct zs_msg *msg_);
+
+        //  Asks pipe to destroy itself.
+        void terminate ();
+
+    private:
+
+        pipe_reader_t (class object_t *parent_, class pipe_t *pipe_,
+            uint64_t hwm_, uint64_t lwm_);
+        ~pipe_reader_t ();
+
+        //  Second step of reader construction. The parameter cannot be passed
+        //  in constructor as peer object doesn't yet exist at the time.
+        void set_peer (class object_t *peer_);
+
+        void process_tail (uint64_t bytes_);
+        void process_terminate_ack ();
+
+        //  The underlying pipe.
+        class pipe_t *pipe;
+
+        //  Pipe writer associated with the other side of the pipe.
+        class object_t *peer;
+
+        //  Associated mux object.
+        struct i_mux *mux;
+
+        //  Index in the associated mux object.
+        int index;
+
+        //  High and low watermarks for in-memory storage (in bytes).
+        uint64_t hwm;
+        uint64_t lwm;
+
+        //  Positions of head and tail of the pipe (in bytes).
+        uint64_t head;
+        uint64_t tail;
+        uint64_t last_sent_head;
+
+        pipe_reader_t (const pipe_reader_t&);
+        void operator = (const pipe_reader_t&);
+    };
+
+}
+
+#endif
diff --git a/src/pipe_writer.cpp b/src/pipe_writer.cpp
new file mode 100644
index 0000000..173cf97
--- /dev/null
+++ b/src/pipe_writer.cpp
@@ -0,0 +1,120 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "pipe_writer.hpp"
+#include "pipe.hpp"
+#include "i_demux.hpp"
+
+zs::pipe_writer_t::pipe_writer_t (object_t *parent_, pipe_t *pipe_,
+      object_t *peer_, uint64_t hwm_, uint64_t lwm_) :
+    object_t (parent_),
+    pipe (pipe_),
+    peer (peer_),
+    demux (NULL),
+    index (-1),
+    hwm (hwm_),
+    lwm (lwm_),
+    head (0),
+    tail (0)
+{
+}
+
+zs::pipe_writer_t::~pipe_writer_t ()
+{
+}
+
+void zs::pipe_writer_t::set_demux (i_demux *demux_)
+{
+    demux = demux_;
+}
+
+void zs::pipe_writer_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zs::pipe_writer_t::get_index ()
+{
+    return index;
+}
+
+bool zs::pipe_writer_t::write (zs_msg *msg_)
+{
+    size_t msg_size = zs_msg_size (msg_);
+
+    //  If message won't fit into the in-memory pipe, there's no way
+    //  to pass it further.
+    //  TODO: It should be discarded and 'oversized' notification should be
+    //        placed into the pipe.
+    zs_assert (!hwm || msg_size <= hwm);
+
+    //  If there's not enough space in the pipe at the moment, return false.
+    if (hwm && tail + msg_size - head > hwm)
+        return false;
+
+    //  Write the message to the pipe and adjust tail position.
+    pipe->write (*msg_);
+    flush ();
+    tail += msg_size;
+
+    return true;
+}
+
+void zs::pipe_writer_t::flush ()
+{
+    if (!pipe->flush ())
+        send_tail (peer, tail);
+}
+
+void zs::pipe_writer_t::process_head (uint64_t bytes_)
+{
+    head = bytes_;
+}
+
+void zs::pipe_writer_t::terminate ()
+{
+    //  Disconnect from the associated demux.
+    if (demux) {
+        demux->detach_pipe (this);
+        demux = NULL;
+    }
+
+    //  Push the delimiter to the pipe. Delimiter is a notification for pipe
+    //  reader that there will be no more messages in the pipe.
+    zs_msg delimiter;
+    delimiter.content = (zs_msg_content*) ZS_DELIMITER;
+    delimiter.shared = false;
+    delimiter.vsm_size = 0;
+    pipe->write (delimiter);
+    flush ();
+}
+
+void zs::pipe_writer_t::process_terminate ()
+{
+    //  Disconnect from the associated demux.
+    if (demux) {
+        demux->detach_pipe (this);
+        demux = NULL;
+    }
+
+    //  Send termination acknowledgement to the pipe reader.
+    send_terminate_ack (peer);
+}
diff --git a/src/pipe_writer.hpp b/src/pipe_writer.hpp
new file mode 100644
index 0000000..3b4b4cd
--- /dev/null
+++ b/src/pipe_writer.hpp
@@ -0,0 +1,88 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_PIPE_WRITER_HPP_INCLUDED__
+#define __ZS_PIPE_WRITER_HPP_INCLUDED__
+
+#include "object.hpp"
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    class pipe_writer_t : public object_t
+    {
+        //  Dispatcher is a friend so that it can create & destroy the writer.
+        //  By making constructor & destructor private we are sure that nobody
+        //  except dispatcher messes with writers.
+        friend class dispatcher_t;
+
+    public:
+
+        //  Set & get index in the associated demux object.
+        void set_demux (struct i_demux *demux_);
+        void set_index (int index_);
+        int get_index ();
+
+        //  Writes a message to the underlying pipe. Returns false if the
+        //  message cannot be written to the pipe at the moment.
+        bool write (struct zs_msg *msg_);
+
+        //  Flush the messages downsteam.
+        void flush ();
+
+        //  Asks pipe to destroy itself.
+        void terminate ();
+
+    private:
+
+        pipe_writer_t (class object_t *parent_, class pipe_t *pipe_,
+            class object_t *peer_, uint64_t hwm_, uint64_t lwm_);
+        ~pipe_writer_t ();
+
+        void process_head (uint64_t bytes_);
+        void process_terminate ();
+
+        //  The underlying pipe.
+        class pipe_t *pipe;
+
+        //  Pipe reader associated with the other side of the pipe.
+        class object_t *peer;
+
+        //  Associated demux object.
+        struct i_demux *demux;
+
+        //  Index in the associated demux object.
+        int index;
+
+        //  High and low watermarks for in-memory storage (in bytes).
+        uint64_t hwm;
+        uint64_t lwm;
+
+        //  Positions of head and tail of the pipe (in bytes).
+        uint64_t head;
+        uint64_t tail;
+
+        pipe_writer_t (const pipe_writer_t&);
+        void operator = (const pipe_writer_t&);
+    };
+
+}
+
+#endif
diff --git a/src/platform.hpp.in b/src/platform.hpp.in
new file mode 100644
index 0000000..108d50d
--- /dev/null
+++ b/src/platform.hpp.in
@@ -0,0 +1,210 @@
+/* src/platform.hpp.in.  Generated from configure.in by autoheader.  */
+
+/* Define to 1 if you have the <arpa/inet.h> header file. */
+#undef HAVE_ARPA_INET_H
+
+/* Define to 1 if you have the <dlfcn.h> header file. */
+#undef HAVE_DLFCN_H
+
+/* Define to 1 if you have the <errno.h> header file. */
+#undef HAVE_ERRNO_H
+
+/* Define to 1 if you have the `freeifaddrs' function. */
+#undef HAVE_FREEIFADDRS
+
+/* Define to 1 if you have the `getifaddrs' function. */
+#undef HAVE_GETIFADDRS
+
+/* Define to 1 if you have the `gettimeofday' function. */
+#undef HAVE_GETTIMEOFDAY
+
+/* Define to 1 if you have the <ifaddrs.h> header file. */
+#undef HAVE_IFADDRS_H
+
+/* Define to 1 if you have the <inttypes.h> header file. */
+#undef HAVE_INTTYPES_H
+
+/* Define to 1 if you have the `nsl' library (-lnsl). */
+#undef HAVE_LIBNSL
+
+/* Define to 1 if you have the `pthread' library (-lpthread). */
+#undef HAVE_LIBPTHREAD
+
+/* Define to 1 if you have the `rt' library (-lrt). */
+#undef HAVE_LIBRT
+
+/* Define to 1 if you have the `socket' library (-lsocket). */
+#undef HAVE_LIBSOCKET
+
+/* Define to 1 if you have the `uuid' library (-luuid). */
+#undef HAVE_LIBUUID
+
+/* Define to 1 if you have the <limits.h> header file. */
+#undef HAVE_LIMITS_H
+
+/* Define to 1 if your system has a GNU libc compatible `malloc' function, and
+   to 0 otherwise. */
+#undef HAVE_MALLOC
+
+/* Define to 1 if you have the <memory.h> header file. */
+#undef HAVE_MEMORY_H
+
+/* Define to 1 if you have the `memset' function. */
+#undef HAVE_MEMSET
+
+/* Define to 1 if you have the <netinet/in.h> header file. */
+#undef HAVE_NETINET_IN_H
+
+/* Define to 1 if you have the <netinet/tcp.h> header file. */
+#undef HAVE_NETINET_TCP_H
+
+/* Define to 1 if you have the `perror' function. */
+#undef HAVE_PERROR
+
+/* Define to 1 if you have the `socket' function. */
+#undef HAVE_SOCKET
+
+/* Define to 1 if stdbool.h conforms to C99. */
+#undef HAVE_STDBOOL_H
+
+/* Define to 1 if you have the <stddef.h> header file. */
+#undef HAVE_STDDEF_H
+
+/* Define to 1 if you have the <stdint.h> header file. */
+#undef HAVE_STDINT_H
+
+/* Define to 1 if you have the <stdlib.h> header file. */
+#undef HAVE_STDLIB_H
+
+/* Define to 1 if you have the <strings.h> header file. */
+#undef HAVE_STRINGS_H
+
+/* Define to 1 if you have the <string.h> header file. */
+#undef HAVE_STRING_H
+
+/* Define to 1 if you have the <sys/eventfd.h> header file. */
+#undef HAVE_SYS_EVENTFD_H
+
+/* Define to 1 if you have the <sys/socket.h> header file. */
+#undef HAVE_SYS_SOCKET_H
+
+/* Define to 1 if you have the <sys/stat.h> header file. */
+#undef HAVE_SYS_STAT_H
+
+/* Define to 1 if you have the <sys/time.h> header file. */
+#undef HAVE_SYS_TIME_H
+
+/* Define to 1 if you have the <sys/types.h> header file. */
+#undef HAVE_SYS_TYPES_H
+
+/* Define to 1 if you have the <unistd.h> header file. */
+#undef HAVE_UNISTD_H
+
+/* Define to 1 if you have the <windows.h> header file. */
+#undef HAVE_WINDOWS_H
+
+/* Define to 1 if the system has the type `_Bool'. */
+#undef HAVE__BOOL
+
+/* Define to 1 if your C compiler doesn't accept -c and -o together. */
+#undef NO_MINUS_C_MINUS_O
+
+/* Name of package */
+#undef PACKAGE
+
+/* Define to the address where bug reports for this package should be sent. */
+#undef PACKAGE_BUGREPORT
+
+/* Define to the full name of this package. */
+#undef PACKAGE_NAME
+
+/* Define to the full name and version of this package. */
+#undef PACKAGE_STRING
+
+/* Define to the one symbol short name of this package. */
+#undef PACKAGE_TARNAME
+
+/* Define to the version of this package. */
+#undef PACKAGE_VERSION
+
+/* Define as the return type of signal handlers (`int' or `void'). */
+#undef RETSIGTYPE
+
+/* Define to 1 if you have the ANSI C header files. */
+#undef STDC_HEADERS
+
+/* Define to 1 if you can safely include both <sys/time.h> and <time.h>. */
+#undef TIME_WITH_SYS_TIME
+
+/* Version number of package */
+#undef VERSION
+
+/* Force to use mutexes */
+#undef ZS_FORCE_MUTEXES
+
+/* Have AIX OS */
+#undef ZS_HAVE_AIX
+
+/* Have eventfd extension. */
+#undef ZS_HAVE_EVENTFD
+
+/* Have FreeBSD OS */
+#undef ZS_HAVE_FREEBSD
+
+/* Have HPUX OS */
+#undef ZS_HAVE_HPUX
+
+/* Have ifaddrs.h header. */
+#undef ZS_HAVE_IFADDRS
+
+/* Have Linux OS */
+#undef ZS_HAVE_LINUX
+
+/* Have MinGW32 */
+#undef ZS_HAVE_MINGW32
+
+/* Have OpenBSD OS */
+#undef ZS_HAVE_OPENBSD
+
+/* Have DarwinOSX OS */
+#undef ZS_HAVE_OSX
+
+/* Have QNX Neutrino OS */
+#undef ZS_HAVE_QNXNTO
+
+/* Have Solaris OS */
+#undef ZS_HAVE_SOLARIS
+
+/* Have Windows OS */
+#undef ZS_HAVE_WINDOWS
+
+/* Define for Solaris 2.5.1 so the uint32_t typedef from <sys/synch.h>,
+   <pthread.h>, or <semaphore.h> is not used. If the typedef was allowed, the
+   #define below would cause a syntax error. */
+#undef _UINT32_T
+
+/* Define to empty if `const' does not conform to ANSI C. */
+#undef const
+
+/* Define to `__inline__' or `__inline' if that's what the C compiler
+   calls it, or to nothing if 'inline' is not supported under any name.  */
+#ifndef __cplusplus
+#undef inline
+#endif
+
+/* Define to rpl_malloc if the replacement function should be used. */
+#undef malloc
+
+/* Define to `unsigned int' if <sys/types.h> does not define. */
+#undef size_t
+
+/* Define to `int' if <sys/types.h> does not define. */
+#undef ssize_t
+
+/* Define to the type of an unsigned integer type of width exactly 32 bits if
+   such a type exists and the standard includes do not define it. */
+#undef uint32_t
+
+/* Define to empty if the keyword `volatile' does not work. Warning: valid
+   code using `volatile' can become incorrect without. Disable with care. */
+#undef volatile
diff --git a/src/poll.cpp b/src/poll.cpp
new file mode 100644
index 0000000..59a0cd7
--- /dev/null
+++ b/src/poll.cpp
@@ -0,0 +1,205 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_LINUX || defined ZS_HAVE_FREEBSD ||\
+    defined ZS_HAVE_OPENBSD || defined ZS_HAVE_SOLARIS ||\
+    defined ZS_HAVE_OSX || defined ZS_HAVE_QNXNTO ||\
+    defined ZS_HAVE_HPUX || defined ZS_HAVE_AIX
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <poll.h>
+#include <algorithm>
+
+#include "poll.hpp"
+#include "err.hpp"
+#include "config.hpp"
+#include "i_poll_events.hpp"
+
+zs::poll_t::poll_t () :
+    retired (false),
+    stopping (false)
+{
+    //  Get the limit on open file descriptors. Resize fds so that it
+    //  can hold all descriptors.
+    rlimit rl;
+    int rc = getrlimit (RLIMIT_NOFILE, &rl);
+    errno_assert (rc != -1);
+    fd_table.resize (rl.rlim_cur);
+
+    for (rlim_t i = 0; i < rl.rlim_cur; i ++)
+        fd_table [i].index = retired_fd;
+}
+
+zs::handle_t zs::poll_t::add_fd (fd_t fd_, i_poll_events *events_)
+{
+    pollfd pfd = {fd_, 0, 0};
+    pollset.push_back (pfd);
+    assert (fd_table [fd_].index == retired_fd);
+
+    fd_table [fd_].index = pollset.size() - 1;
+    fd_table [fd_].events = events_;
+
+    //  Increase the load metric of the thread.
+    load.add (1);
+
+    handle_t handle;
+    handle.fd = fd_;
+    return handle;
+}
+
+void zs::poll_t::rm_fd (handle_t handle_)
+{
+    fd_t index = fd_table [handle_.fd].index;
+    assert (index != retired_fd);
+
+    //  Mark the fd as unused.
+    pollset [index].fd = retired_fd;
+    fd_table [handle_.fd].index = retired_fd;
+    retired = true;
+
+    //  Decrease the load metric of the thread.
+    load.sub (1);
+}
+
+void zs::poll_t::set_pollin (handle_t handle_)
+{
+    int index = fd_table [handle_.fd].index;
+    pollset [index].events |= POLLIN;
+}
+
+void zs::poll_t::reset_pollin (handle_t handle_)
+{
+    int index = fd_table [handle_.fd].index;
+    pollset [index].events &= ~((short) POLLIN);
+}
+
+void zs::poll_t::set_pollout (handle_t handle_)
+{
+    int index = fd_table [handle_.fd].index;
+    pollset [index].events |= POLLOUT;
+}
+
+void zs::poll_t::reset_pollout (handle_t handle_)
+{
+    int index = fd_table [handle_.fd].index;
+    pollset [index].events &= ~((short) POLLOUT);
+}
+
+void zs::poll_t::add_timer (i_poll_events *events_)
+{
+     timers.push_back (events_);
+}
+
+void zs::poll_t::cancel_timer (i_poll_events *events_)
+{
+    timers_t::iterator it = std::find (timers.begin (), timers.end (), events_);
+    if (it != timers.end ())
+        timers.erase (it);
+}
+
+int zs::poll_t::get_load ()
+{
+    return load.get ();
+}
+
+void zs::poll_t::start ()
+{
+    worker.start (worker_routine, this);
+}
+
+void zs::poll_t::stop ()
+{
+    stopping = true;
+}
+
+void zs::poll_t::join ()
+{
+    worker.stop ();
+}
+
+void zs::poll_t::loop ()
+{
+    while (!stopping) {
+
+        //  Wait for events.
+        int rc = poll (&pollset [0], pollset.size (),
+            timers.empty () ? -1 : max_timer_period);
+        if (rc == -1 && errno == EINTR)
+            continue;
+        errno_assert (rc != -1);
+
+        //  Handle timer.
+        if (!rc) {
+
+            //  Use local list of timers as timer handlers may fill new timers
+            //  into the original array.
+            timers_t t;
+            std::swap (timers, t);
+
+            //  Trigger all the timers.
+            for (timers_t::iterator it = t.begin (); it != t.end (); it ++)
+                (*it)->timer_event ();
+
+            continue;
+        }
+
+        for (pollset_t::iterator it = pollset.begin ();
+                it != pollset.end (); it ++) {
+
+            zs_assert (!(it->revents & POLLNVAL));
+            if (it->fd == retired_fd)
+               continue;
+            if (it->revents & (POLLERR | POLLHUP))
+                fd_table [it->fd].events->in_event ();
+            if (it->fd == retired_fd)
+               continue;
+            if (it->revents & POLLOUT)
+                fd_table [it->fd].events->out_event ();
+            if (it->fd == retired_fd)
+               continue;
+            if (it->revents & POLLIN)
+                fd_table [it->fd].events->in_event ();
+        }
+
+        //  Clean up the pollset and update the fd_table accordingly.
+        if (retired) {
+            pollset_t::size_type i = 0;
+            while (i < pollset.size ()) {
+                if (pollset [i].fd == retired_fd)
+                    pollset.erase (pollset.begin () + i);
+                else {
+                    fd_table [pollset [i].fd].index = i;
+                    i ++;
+                }
+            }
+            retired = false;
+        }
+    }
+}
+
+void zs::poll_t::worker_routine (void *arg_)
+{
+    ((poll_t*) arg_)->loop ();
+}
+
+#endif
diff --git a/src/poll.hpp b/src/poll.hpp
new file mode 100644
index 0000000..65095f7
--- /dev/null
+++ b/src/poll.hpp
@@ -0,0 +1,112 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_POLL_HPP_INCLUDED__
+#define __ZS_POLL_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_LINUX || defined ZS_HAVE_FREEBSD ||\
+    defined ZS_HAVE_OPENBSD || defined ZS_HAVE_SOLARIS ||\
+    defined ZS_HAVE_OSX || defined ZS_HAVE_QNXNTO ||\
+    defined ZS_HAVE_HPUX || defined ZS_HAVE_AIX
+
+#include <poll.h>
+#include <stddef.h>
+#include <vector>
+
+#include "i_poller.hpp"
+#include "fd.hpp"
+#include "thread.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  Implements socket polling mechanism using the POSIX.1-2001
+    //  poll() system call.
+
+    class poll_t : public i_poller
+    {
+    public:
+
+        poll_t ();
+        virtual ~poll_t () {}
+
+        //  i_poller implementation.
+        handle_t add_fd (fd_t fd_, i_poll_events *events_);
+        void rm_fd (handle_t handle_);
+        void set_pollin (handle_t handle_);
+        void reset_pollin (handle_t handle_);
+        void set_pollout (handle_t handle_);
+        void reset_pollout (handle_t handle_);
+        void add_timer (i_poll_events *events_);
+        void cancel_timer (i_poll_events *events_);
+        int get_load ();
+        void start ();
+        void stop ();
+        void join ();
+
+    private:
+
+        //  Main worker thread routine.
+        static void worker_routine (void *arg_);
+
+        //  Main event loop.
+        void loop ();
+
+        struct fd_entry_t
+        {
+            fd_t index;
+            struct i_poll_events *events;
+        };
+
+        //  This table stores data for registered descriptors.
+        std::vector <fd_entry_t> fd_table;
+
+        //  Pollset to pass to the poll function.
+        typedef std::vector <pollfd> pollset_t;
+        pollset_t pollset;
+
+        //  If true, there's at least one retired event source.
+        bool retired;
+
+        //  List of all the engines waiting for the timer event.
+        typedef std::vector <struct i_poll_events*> timers_t;
+        timers_t timers;
+
+        //  If true, thread is in the process of shutting down.
+        bool stopping;
+
+        //  Handle of the physical thread doing the I/O work.
+        thread_t worker;
+
+        //  Load of the poller. Currently number of file descriptors
+        //  registered with the poller.
+        atomic_counter_t load;
+
+        poll_t (const poll_t&);
+        void operator = (const poll_t&);
+    };
+
+}
+
+#endif
+
+#endif
diff --git a/src/pub.cpp b/src/pub.cpp
new file mode 100644
index 0000000..70add18
--- /dev/null
+++ b/src/pub.cpp
@@ -0,0 +1,38 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "pub.hpp"
+#include "app_thread.hpp"
+#include "session.hpp"
+#include "err.hpp"
+
+zs::pub_t::pub_t (app_thread_t *thread_, session_t *session_) :
+    socket_base_t (thread_, session_)
+{
+    disable_in ();
+}
+
+int zs::pub_t::recv (struct zs_msg *msg_, int flags_)
+{
+    //  Publisher socket has no recv function.
+    errno = ENOTSUP;
+    return -1;
+}
diff --git a/src/pub.hpp b/src/pub.hpp
new file mode 100644
index 0000000..b071318
--- /dev/null
+++ b/src/pub.hpp
@@ -0,0 +1,45 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_PUB_HPP_INCLUDED__
+#define __ZS_PUB_HPP_INCLUDED__
+
+#include "socket_base.hpp"
+
+namespace zs
+{
+
+    class pub_t : public socket_base_t
+    {
+    public:
+
+        pub_t (class app_thread_t *thread_, class session_t *session_);
+
+        //  i_api overloads.
+        int recv (struct zs_msg *msg_, int flags_);
+
+    private:
+
+        pub_t (const pub_t&);
+        void operator = (const pub_t&);
+    };
+
+}
+
+#endif
diff --git a/src/rep.cpp b/src/rep.cpp
new file mode 100644
index 0000000..586c7ed
--- /dev/null
+++ b/src/rep.cpp
@@ -0,0 +1,29 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "rep.hpp"
+#include "app_thread.hpp"
+#include "session.hpp"
+
+zs::rep_t::rep_t (app_thread_t *thread_, session_t *session_) :
+    socket_base_t (thread_, session_)
+{
+}
diff --git a/src/rep.hpp b/src/rep.hpp
new file mode 100644
index 0000000..e11eaa3
--- /dev/null
+++ b/src/rep.hpp
@@ -0,0 +1,42 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_REP_HPP_INCLUDED__
+#define __ZS_REP_HPP_INCLUDED__
+
+#include "socket_base.hpp"
+
+namespace zs
+{
+
+    class rep_t : public socket_base_t
+    {
+    public:
+
+        rep_t (class app_thread_t *thread_, class session_t *session_);
+
+    private:
+
+        rep_t (const rep_t&);
+        void operator = (const rep_t&);
+    };
+
+}
+
+#endif
diff --git a/src/req.cpp b/src/req.cpp
new file mode 100644
index 0000000..d7a9ad7
--- /dev/null
+++ b/src/req.cpp
@@ -0,0 +1,29 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "req.hpp"
+#include "app_thread.hpp"
+#include "session.hpp"
+
+zs::req_t::req_t (app_thread_t *thread_, session_t *session_) :
+    socket_base_t (thread_, session_)
+{
+}
diff --git a/src/req.hpp b/src/req.hpp
new file mode 100644
index 0000000..678897d
--- /dev/null
+++ b/src/req.hpp
@@ -0,0 +1,42 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_REQ_HPP_INCLUDED__
+#define __ZS_REQ_HPP_INCLUDED__
+
+#include "socket_base.hpp"
+
+namespace zs
+{
+
+    class req_t : public socket_base_t
+    {
+    public:
+
+        req_t (class app_thread_t *thread_, class session_t *session_);
+
+    private:
+
+        req_t (const req_t&);
+        void operator = (const req_t&);
+    };
+
+}
+
+#endif
diff --git a/src/safe_object.cpp b/src/safe_object.cpp
new file mode 100644
index 0000000..a7c72e6
--- /dev/null
+++ b/src/safe_object.cpp
@@ -0,0 +1,76 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "safe_object.hpp"
+
+zs::safe_object_t::safe_object_t (class dispatcher_t *dispatcher_,
+      int thread_slot_) :
+    object_t (dispatcher_, thread_slot_),
+    processed_seqnum (0),
+    terminating (false)
+{
+}
+
+zs::safe_object_t::safe_object_t (object_t *parent_) :
+    object_t (parent_),
+    processed_seqnum (0),
+    terminating (false)
+{
+}
+
+void zs::safe_object_t::inc_seqnum ()
+{
+    //  This function is called from the sender thread to ensure that this
+    //  object will still exist when the command sent to it arrives in the
+    //  destination thread.
+    sent_seqnum.add (1);
+}
+
+void zs::safe_object_t::process_command (struct command_t &cmd_)
+{
+    object_t::process_command (cmd_);
+
+    //  Adjust sequence number of the last processed command.
+    processed_seqnum++;
+
+    //  If we are already in the termination phase and all commands sent to
+    //  this object are processed, it's safe to deallocate it.
+    if (terminating && sent_seqnum.get () == processed_seqnum)
+        delete this;
+}
+
+void zs::safe_object_t::terminate ()
+{
+    //  Wait till all commands sent to this session are processed.
+    terminating = true;
+
+    //  If there's no pending command we can deallocate the session
+    //  straight saway.
+    if (sent_seqnum.get () == processed_seqnum)
+        delete this;
+}
+
+bool zs::safe_object_t::is_terminating ()
+{
+    return terminating;
+}
+
+zs::safe_object_t::~safe_object_t ()
+{
+}
diff --git a/src/safe_object.hpp b/src/safe_object.hpp
new file mode 100644
index 0000000..efa0d2f
--- /dev/null
+++ b/src/safe_object.hpp
@@ -0,0 +1,68 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SAFE_OBJECT_HPP_INCLUDED__
+#define __ZS_SAFE_OBJECT_HPP_INCLUDED__
+
+#include "object.hpp"
+#include "atomic_counter.hpp"	
+
+namespace zs
+{
+
+    //  Same as object_t with the exception of termination mechanism. While
+    //  object_t is destroyed immediately on terminate (assuming that the caller
+    //  have ensured that there are no more commands for the object on the
+    //  fly), safe_object_t switches into termination mode and waits for all
+    //  the on-the-fly commands to be delivered before it deallocates itself.
+
+    class safe_object_t : public object_t
+    {
+    public:
+
+        safe_object_t (class dispatcher_t *dispatcher_, int thread_slot_);
+        safe_object_t (object_t *parent_);
+
+        void inc_seqnum ();
+        void process_command (struct command_t &cmd_);
+
+    protected:
+
+        void terminate ();
+        bool is_terminating ();
+
+        virtual ~safe_object_t ();
+
+    private:
+
+        //  Sequence number of the last command sent to the object and last
+        //  command processed by the object. The former is an atomic counter
+        //  meaning that other threads can increment it safely.
+        atomic_counter_t sent_seqnum;
+        uint32_t processed_seqnum;
+
+        bool terminating;
+
+        safe_object_t (const safe_object_t&);
+        void operator = (const safe_object_t&);
+    };
+
+}
+
+#endif
diff --git a/src/select.cpp b/src/select.cpp
new file mode 100644
index 0000000..9776db3
--- /dev/null
+++ b/src/select.cpp
@@ -0,0 +1,236 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+
+#include <string.h>
+#include <algorithm>
+
+#ifdef ZS_HAVE_WINDOWS
+#include "winsock2.h"
+#elif defined ZS_HAVE_HPUX
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/time.h>
+#elif defined ZS_HAVE_OPENVMS
+#include <sys/types.h>
+#include <sys/time.h>
+#else
+#include <sys/select.h>
+#endif
+
+#include "select.hpp"
+#include "err.hpp"
+#include "config.hpp"
+#include "i_poll_events.hpp"
+
+zs::select_t::select_t () :
+    maxfd (retired_fd),
+    retired (false),
+    stopping (false)
+{
+    //  Clear file descriptor sets.
+    FD_ZERO (&source_set_in);
+    FD_ZERO (&source_set_out);
+    FD_ZERO (&source_set_err);
+}
+
+zs::handle_t zs::select_t::add_fd (fd_t fd_, i_poll_events *events_)
+{
+    //  Store the file descriptor.
+    fd_entry_t entry = {fd_, events_};
+    fds.push_back (entry);
+
+    //  Start polling on errors.
+    FD_SET (fd_, &source_set_err);
+
+    //  Adjust maxfd if necessary.
+    if (fd_ > maxfd)
+        maxfd = fd_;
+
+    //  Increase the load metric of the thread.
+    load.add (1);
+
+    handle_t handle;
+    handle.fd = fd_;
+    return handle;
+}
+
+void zs::select_t::rm_fd (handle_t handle_)
+{
+    //  Get file descriptor.
+    fd_t fd = handle_.fd;
+
+    //  Mark the descriptor as retired.
+    fd_set_t::iterator it;
+    for (it = fds.begin (); it != fds.end (); it ++)
+        if (it->fd == fd)
+            break;
+    zs_assert (it != fds.end ());
+    it->fd = retired_fd;
+    retired = true;
+
+    //  Stop polling on the descriptor.
+    FD_CLR (fd, &source_set_in);
+    FD_CLR (fd, &source_set_out);
+    FD_CLR (fd, &source_set_err);
+
+    //  Discard all events generated on this file descriptor.
+    FD_CLR (fd, &readfds);
+    FD_CLR (fd, &writefds);
+    FD_CLR (fd, &exceptfds);
+
+    //  Adjust the maxfd attribute if we have removed the
+    //  highest-numbered file descriptor.
+    if (fd == maxfd) {
+        maxfd = retired_fd;
+        for (fd_set_t::iterator it = fds.begin (); it != fds.end (); it ++)
+            if (it->fd > maxfd)
+                maxfd = it->fd;
+    }
+
+    //  Decrease the load metric of the thread.
+    load.sub (1);
+}
+
+void zs::select_t::set_pollin (handle_t handle_)
+{
+    FD_SET (handle_.fd, &source_set_in);
+}
+
+void zs::select_t::reset_pollin (handle_t handle_)
+{
+    FD_CLR (handle_.fd, &source_set_in);
+}
+
+void zs::select_t::set_pollout (handle_t handle_)
+{
+    FD_SET (handle_.fd, &source_set_out);
+}
+
+void zs::select_t::reset_pollout (handle_t handle_)
+{
+    FD_CLR (handle_.fd, &source_set_out);
+}
+
+void zs::select_t::add_timer (i_poll_events *events_)
+{
+    timers.push_back (events_);
+}
+
+void zs::select_t::cancel_timer (i_poll_events *events_)
+{
+    timers_t::iterator it = std::find (timers.begin (), timers.end (), events_);
+    if (it != timers.end ())
+        timers.erase (it);
+}
+
+int zs::select_t::get_load ()
+{
+    return load.get ();
+}
+
+void zs::select_t::start ()
+{
+    worker.start (worker_routine, this);
+}
+
+void zs::select_t::stop ()
+{
+    stopping = true;
+}
+
+void zs::select_t::join ()
+{
+    worker.stop ();
+}
+
+void zs::select_t::loop ()
+{
+    while (!stopping) {
+
+        //  Intialise the pollsets.
+        memcpy (&readfds, &source_set_in, sizeof source_set_in);
+        memcpy (&writefds, &source_set_out, sizeof source_set_out);
+        memcpy (&exceptfds, &source_set_err, sizeof source_set_err);
+
+        //  Compute the timout interval. Select is free to overwrite the
+        //  value so we have to compute it each time anew.
+        timeval timeout = {max_timer_period / 1000,
+            (max_timer_period % 1000) * 1000};
+
+        //  Wait for events.
+        int rc = select (maxfd + 1, &readfds, &writefds, &exceptfds,
+            timers.empty () ? NULL : &timeout);
+
+#ifdef ZS_HAVE_WINDOWS
+        wsa_assert (rc != SOCKET_ERROR);
+#else
+        if (rc == -1 && errno == EINTR)
+            continue;
+        errno_assert (rc != -1);
+#endif
+
+        //  Handle timer.
+        if (!rc) {
+
+            //  Use local list of timers as timer handlers may fill new timers
+            //  into the original array.
+            timers_t t;
+            std::swap (timers, t);
+
+            //  Trigger all the timers.
+            for (timers_t::iterator it = t.begin (); it != t.end (); it ++)
+                (*it)->timer_event ();
+
+            continue;
+        }
+
+        for (fd_set_t::size_type i = 0; i < fds.size (); i ++) {
+            if (fds [i].fd == retired_fd)
+                continue;
+            if (FD_ISSET (fds [i].fd, &exceptfds))
+                fds [i].events->in_event ();
+            if (fds [i].fd == retired_fd)
+                continue;
+            if (FD_ISSET (fds [i].fd, &writefds))
+                fds [i].events->out_event ();
+            if (fds [i].fd == retired_fd)
+                continue;
+            if (FD_ISSET (fds [i].fd, &readfds))
+                fds [i].events->in_event ();
+        }
+
+        //  Destroy retired event sources.
+        if (retired) {
+            for (fd_set_t::size_type i = 0; i < fds.size (); i ++) {
+                if (fds [i].fd == retired_fd) {
+                    fds.erase (fds.begin () + i);
+                    i --;
+                }
+            }
+            retired = false;
+        }
+    }
+}
+
+void zs::select_t::worker_routine (void *arg_)
+{
+    ((select_t*) arg_)->loop ();
+}
diff --git a/src/select.hpp b/src/select.hpp
new file mode 100644
index 0000000..7151f84
--- /dev/null
+++ b/src/select.hpp
@@ -0,0 +1,122 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SELECT_HPP_INCLUDED__
+#define __ZS_SELECT_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#include <stddef.h>
+#include <vector>
+
+#ifdef ZS_HAVE_WINDOWS
+#include "winsock2.h"
+#elif defined ZS_HAVE_OPENVMS
+#include <sys/types.h>
+#include <sys/time.h>
+#else
+#include <sys/select.h>
+#endif
+
+#include "i_poller.hpp"
+#include "fd.hpp"
+#include "thread.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  Implements socket polling mechanism using POSIX.1-2001 select()
+    //  function.
+
+    class select_t : public i_poller
+    {
+    public:
+
+        select_t ();
+
+        //  i_poller implementation.
+        handle_t add_fd (fd_t fd_, i_poll_events *events_);
+        void rm_fd (handle_t handle_);
+        void set_pollin (handle_t handle_);
+        void reset_pollin (handle_t handle_);
+        void set_pollout (handle_t handle_);
+        void reset_pollout (handle_t handle_);
+        void add_timer (i_poll_events *events_);
+        void cancel_timer (i_poll_events *events_);
+        int get_load ();
+        void start ();
+        void stop ();
+        void join ();
+
+    private:
+
+        //  Main worker thread routine.
+        static void worker_routine (void *arg_);
+
+        //  Main event loop.
+        void loop ();
+
+        struct fd_entry_t
+        {
+            fd_t fd;
+            struct i_poll_events *events;
+        };
+
+        //  Set of file descriptors that are used to retreive
+        //  information for fd_set.
+        typedef std::vector <fd_entry_t> fd_set_t;
+        fd_set_t fds;
+
+        fd_set source_set_in;
+        fd_set source_set_out;
+        fd_set source_set_err;
+
+        fd_set readfds;
+        fd_set writefds;
+        fd_set exceptfds;
+
+        //  Maximum file descriptor.
+        fd_t maxfd;
+
+        //  If true, at least one file descriptor has retired.
+        bool retired;
+
+        //  List of all the engines waiting for the timer event.
+        typedef std::vector <struct i_poll_events*> timers_t;
+        timers_t timers;
+
+        //  If true, thread is shutting down.
+        bool stopping;
+
+        //  Handle of the physical thread doing the I/O work.
+        thread_t worker;
+
+        //  Load of the poller. Currently number of file descriptors
+        //  registered with the poller.
+        atomic_counter_t load;
+
+        select_t (const select_t&);
+        void operator = (const select_t&);
+    };
+
+}
+
+#endif
+
diff --git a/src/session.cpp b/src/session.cpp
new file mode 100644
index 0000000..63868b2
--- /dev/null
+++ b/src/session.cpp
@@ -0,0 +1,273 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "session.hpp"
+#include "i_engine.hpp"
+#include "i_thread.hpp"
+#include "i_mux.hpp"
+#include "i_demux.hpp"
+#include "err.hpp"
+#include "pipe.hpp"
+#include "pipe_reader.hpp"
+#include "pipe_writer.hpp"
+#include "simple_semaphore.hpp"
+
+zs::session_t::session_t (object_t *parent_, i_thread *thread_,
+      i_mux *mux_, i_demux *demux_,
+      bool terminate_on_disconnect_, bool terminate_on_no_pipes_) :
+    safe_object_t (parent_),
+    mux (mux_),
+    demux (demux_),
+    thread (thread_),
+    engine (NULL),
+    terminate_on_disconnect (terminate_on_disconnect_),
+    terminate_on_no_pipes (false),
+    terminate_on_no_pipes_delayed (terminate_on_no_pipes_),
+    index (-1)
+{
+    //  At least one way to terminate the session should be allowed. Otherwise
+    //  the session can be orphaned forever.
+    zs_assert (terminate_on_disconnect || terminate_on_no_pipes_delayed);
+
+    //  Give the mux and the demux callback pointer to ourselves.
+    if (mux)
+        mux->set_session (this);
+    if (demux)
+        demux->set_session (this);
+}
+
+void zs::session_t::shutdown ()
+{
+    //  Session may live even without an associated engine, thus we have
+    //  to check if for NULL value.
+    if (engine)
+        engine->shutdown ();
+
+    //  Propagate the shutdown signal to both inbound and outbound pipes.
+    if (mux)
+        mux->shutdown ();
+    if (demux)
+        demux->shutdown ();
+
+    delete this;
+}
+
+void zs::session_t::disconnected ()
+{
+    //  It's engine who calls this function so there's no need to deallocate
+    //  the engine. Just drop the reference.
+    engine = NULL;
+
+    //  Some sessions won't shut down because of disconnect. New engine will
+    //  attached to the session later on.
+    if (!terminate_on_disconnect)
+        return;
+
+    terminate ();
+}
+
+void zs::session_t::bind (object_t *peer_, bool in_, bool out_)
+{
+    //  Create the out pipe (if required).
+    pipe_reader_t *pipe_reader = NULL;
+    if (out_) {
+        pipe_writer_t *pipe_writer;
+        create_pipe (peer_, this, 0, 0, &pipe_reader, &pipe_writer);
+        demux->attach_pipe (pipe_writer);
+
+        //  There's at least one pipe attached. We can deallocate the object
+        //  when there are no pipes (if required).
+        terminate_on_no_pipes = terminate_on_no_pipes_delayed;
+    }
+
+    //  Ask peer to attach to the out pipe (if one exists). If required, ask
+    //  it to create a pipe in opposite direction. It's assumed that peer's
+    //  seqnum was already incremented, so we don't need to care whether it's
+    //  alive at the moment.
+    if (in_)
+        inc_seqnum ();
+    send_bind (peer_, pipe_reader, in_ ? this : NULL);
+}
+
+void zs::session_t::revive ()
+{
+    if (engine)
+        engine->revive ();
+}
+
+void zs::session_t::terminate ()
+{
+    //  Terminate is always called by engine, thus it'll terminate itself,
+    //  we just have to drop the pointer.
+    engine = NULL;
+
+    //  Propagate the terminate signal to both inbound and outbound pipes.
+    if (mux) {
+        mux->terminate ();
+        mux = NULL;
+    }
+    if (demux) {
+        demux->terminate ();
+        demux = NULL;
+    }
+
+    //  Session cannot be deallocated at this point. There can still be
+    //  pending commands to process. Unregister session from global
+    //  repository thus ensuring that no new commands will be sent.
+    unregister_inproc_endpoints (this);
+
+    //  Move to terminating state.
+    safe_object_t::terminate ();
+}
+
+zs::session_t::~session_t ()
+{
+    //  When session is actually deallocated it unregisters from its thread.
+    //  Unregistration cannot be done earlier as it would result in memory
+    //  leak if global shutdown happens in the middle of session termination.
+    thread->detach_session (this);
+}
+
+void zs::session_t::set_engine (i_engine *engine_)
+{
+    zs_assert (!engine || !engine_);
+    engine = engine_;
+}
+
+void zs::session_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zs::session_t::get_index ()
+{
+    return index;
+}
+
+bool zs::session_t::write (zs_msg *msg_)
+{
+    return demux->send (msg_);
+}
+
+void zs::session_t::flush ()
+{
+    demux->flush ();
+}
+
+bool zs::session_t::read (zs_msg *msg_)
+{
+    bool retrieved = mux->recv (msg_);
+    if (terminate_on_no_pipes && mux->empty () && demux->empty ()) {
+        zs_assert (engine);
+        engine->schedule_terminate ();
+        terminate ();
+    }
+    return retrieved;
+}
+
+void zs::session_t::process_bind (pipe_reader_t *reader_, session_t *peer_)
+{
+    if (is_terminating ()) {
+
+        //  If session is already in termination phase, we'll ask newly arrived
+        //  pipe reader & writer to terminate straight away.
+        if (reader_)
+            reader_->terminate ();
+
+        //  Peer session has already incremented its seqnum. We have to send
+        //  a dummy command to avoid a memory leak.
+        if (peer_)
+            send_bind (peer_, NULL, NULL);
+
+        return;
+    }
+
+    //  If inbound pipe is provided, bind it to the mux.
+    if (reader_) {
+        mux->attach_pipe (reader_);
+
+        //  There's at least one pipe attached. We can deallocate the object
+        //  when there are no pipes (if required).
+        terminate_on_no_pipes = terminate_on_no_pipes_delayed;
+    }
+
+    //  If peer wants to get messages from ourselves, we'll bind to it.
+    if (peer_) {
+        pipe_reader_t *pipe_reader;
+        pipe_writer_t *pipe_writer;
+        create_pipe (peer_, this, 0, 0, &pipe_reader, &pipe_writer);
+        demux->attach_pipe (pipe_writer);
+        send_bind (peer_, pipe_reader, NULL);
+
+        //  There's at least one pipe attached. We can deallocate the object
+        //  when there are no pipes (if required).
+        terminate_on_no_pipes = terminate_on_no_pipes_delayed;
+    }
+}
+
+void zs::session_t::process_reg (simple_semaphore_t *smph_)
+{
+    zs_assert (!is_terminating ());
+
+    //  Add the session to the list of sessions associated with this I/O thread.
+    //  This way the session will be deallocated on the terminal shutdown.
+    thread->attach_session (this);
+
+    //  Release calling thead (if required).
+    if (smph_)
+        smph_->post ();
+}
+
+void zs::session_t::process_reg_and_bind (session_t *peer_,
+    bool flow_in_, bool flow_out_)
+{
+    zs_assert (!is_terminating ());
+
+    //  Add the session to the list of sessions associated with this I/O thread.
+    //  This way the session will be deallocated on the terminal shutdown.
+    thread->attach_session (this);
+
+    //  Bind to the peer. Note that caller have already incremented command
+    //  sequence number of the peer so we are sure it still exists.
+    pipe_reader_t *pipe_reader = NULL;
+    if (flow_out_) {
+        pipe_writer_t *pipe_writer;
+        create_pipe (peer_, this, 0, 0, &pipe_reader, &pipe_writer);
+        demux->attach_pipe (pipe_writer);
+
+        //  There's at least one pipe attached. We can deallocate the object
+        //  when there are no pipes (if required).
+        terminate_on_no_pipes = terminate_on_no_pipes_delayed;
+    }
+    send_bind (peer_, pipe_reader, flow_in_ ? this : NULL);
+}
+
+void zs::session_t::process_engine (i_engine *engine_)
+{
+    if (is_terminating ()) {
+
+        //  Kill the engine. It won't be needed anymore.
+        engine_->terminate ();
+        return;
+    }
+
+    engine_->attach (thread->get_poller (), this);
+}
diff --git a/src/session.hpp b/src/session.hpp
new file mode 100644
index 0000000..3cdace2
--- /dev/null
+++ b/src/session.hpp
@@ -0,0 +1,107 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SESSION_HPP_INCLUDED__
+#define __ZS_SESSION_HPP_INCLUDED__
+
+#include "i_session.hpp"
+#include "safe_object.hpp"
+#include "stdint.hpp"
+#include "atomic_counter.hpp"
+
+namespace zs
+{
+
+    //  Object that encapsulates both mux and demux.
+
+    class session_t : public safe_object_t, public i_session
+    {
+    public:
+
+        //  Creates the session object.
+        session_t (struct object_t *parent_, struct i_thread *thread_,
+            struct i_mux *mux_, struct i_demux *demux_,
+            bool terminate_on_disconnect_, bool terminate_on_no_pipes_);
+
+        //  i_session implementation
+        void set_engine (struct i_engine *engine_);
+        void shutdown ();
+        bool read (struct zs_msg *msg_);
+        bool write (struct zs_msg *msg_);
+        void flush ();
+
+        //  Called by the engine when it is being closed.
+        void disconnected ();
+
+        //  Creates a message flow between this session and the peer session.
+        //  If in_ is true, the messages can flow from the peer to ourselves.
+        //  If out_ is true, messages can flow from ourselves to the peer.
+        //  It's assumed that peer's seqnum was already incremented.
+        void bind (class object_t *peer_, bool in_, bool out_);
+
+        //  Called by mux if new messages are available.
+        void revive ();
+
+        //  Functions to set & retrieve index of this MD in thread's array
+        //  of session objects.
+        void set_index (int index_);
+        int get_index ();
+
+    private:
+
+        //  Clean-up.
+        ~session_t ();
+
+        //  Terminate is private here. It is called by either when disconnected
+        //  or no_pipes event occurs.
+        void terminate ();
+
+        void process_bind (class pipe_reader_t *reader_,
+            class session_t *peer_);
+        void process_reg (class simple_semaphore_t *smph_);
+        void process_reg_and_bind (class session_t *peer_,
+            bool flow_in_, bool flow_out_);
+        void process_engine (i_engine *engine_);
+
+        struct i_mux *mux;
+        struct i_demux *demux;
+
+        struct i_thread *thread;
+        struct i_engine *engine;
+
+        //  If true termination of the session can be triggered by engine
+        //  disconnect/close.
+        bool terminate_on_disconnect;
+
+        //  If true termination of the session can be triggered when the last
+        //  pipe detaches from it.
+        bool terminate_on_no_pipes;
+
+        //  If true, terminate_on_no_pipes should be set when at least one
+        //  pipe was bound.
+        bool terminate_on_no_pipes_delayed;
+
+        //  Index in thread's session array.
+        int index;
+    };
+
+}
+
+#endif
+
diff --git a/src/session_stub.cpp b/src/session_stub.cpp
new file mode 100644
index 0000000..3bebcb0
--- /dev/null
+++ b/src/session_stub.cpp
@@ -0,0 +1,110 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string>
+
+#include "../include/zs.h"
+
+#include "session_stub.hpp"
+#include "i_engine.hpp"
+#include "listener.hpp"
+#include "err.hpp"
+
+zs::session_stub_t::session_stub_t (listener_t *listener_) :
+    state (reading_identity),
+    engine (NULL),
+    listener (listener_),
+    index (-1)
+{
+}
+
+void zs::session_stub_t::terminate ()
+{
+    if (engine)
+        engine->terminate ();
+    delete this;
+}
+
+void zs::session_stub_t::shutdown ()
+{
+    if (engine)
+        engine->shutdown ();
+    delete this;
+}
+
+zs::session_stub_t::~session_stub_t ()
+{
+}
+
+void zs::session_stub_t::set_engine (i_engine *engine_)
+{
+    zs_assert (!engine_ || !engine);
+    engine = engine_;
+}
+
+bool zs::session_stub_t::read (struct zs_msg *msg_)
+{
+    //  No messages are sent to the connecting peer.
+    return false;
+}
+
+bool zs::session_stub_t::write (struct zs_msg *msg_)
+{
+    //  The first message arrived is the connection identity.
+    if (state == reading_identity) {
+        identity = std::string ((const char*) zs_msg_data (msg_),
+            zs_msg_size (msg_));
+        state = has_identity;
+        return true;
+    }
+
+    //  We are not interested in any subsequent messages.
+    return false;
+}
+
+void zs::session_stub_t::flush ()
+{
+    //  We have the identity. At this point we can find the correct session and
+    //  attach it to the connection.
+    if (state == has_identity) {
+
+        //  At this point the stub will be deleted. Return immediately without
+        //  touching 'this' pointer.
+        listener->got_identity (this, identity.c_str ());
+        return;
+    }
+}
+
+zs::i_engine *zs::session_stub_t::detach_engine ()
+{
+    //  Ask engine to unregister from the poller.
+    i_engine *e = engine;
+    engine->detach ();
+    return e;
+}
+
+void zs::session_stub_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zs::session_stub_t::get_index ()
+{
+    return index;
+}
diff --git a/src/session_stub.hpp b/src/session_stub.hpp
new file mode 100644
index 0000000..2e882f8
--- /dev/null
+++ b/src/session_stub.hpp
@@ -0,0 +1,83 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SESSION_STUB_HPP_INCLUDED__
+#define __ZS_SESSION_STUB_HPP_INCLUDED__
+
+#include <string>
+
+#include "i_session.hpp"
+
+namespace zs
+{
+
+    //  This class is used instead of regular session till the identity of
+    //  incomming connection is established and connection is attached
+    //  to corresponding session.
+
+    class session_stub_t : public i_session
+    {
+    public:
+
+        session_stub_t (class listener_t *listener_);
+
+        //  i_session implementation.
+        void set_engine (struct i_engine *engine_);
+        void terminate ();
+        void shutdown ();
+        bool read (struct zs_msg *msg_);
+        bool write (struct zs_msg *msg_);
+        void flush ();
+
+        //  Detaches engine from the stub. Returns it to the caller.
+        struct i_engine *detach_engine ();
+
+        //  Manipulate stubs's index in listener's array of stubs.
+        void set_index (int index_);
+        int get_index ();
+
+    private:
+
+        //  Clean-up.
+        virtual ~session_stub_t ();
+
+        enum {
+            reading_identity,
+            has_identity
+        } state;
+
+        //  Reference to the associated engine.
+        i_engine *engine;
+
+        //  Reference to the listener object that owns this stub.
+        class listener_t *listener;
+
+        //  Index of the stub in listener's array of stubs.
+        int index;
+
+        //  Identity of the connection.
+        std::string identity;
+
+        session_stub_t (const session_stub_t&);
+        void operator = (const session_stub_t&);
+    };
+
+}
+
+#endif
diff --git a/src/simple_semaphore.hpp b/src/simple_semaphore.hpp
new file mode 100644
index 0000000..1bd114f
--- /dev/null
+++ b/src/simple_semaphore.hpp
@@ -0,0 +1,188 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SIMPLE_SEMAPHORE_HPP_INCLUDED__
+#define __ZS_SIMPLE_SEMAPHORE_HPP_INCLUDED__
+
+#include "platform.hpp"
+#include "err.hpp"
+
+#if defined ZS_HAVE_LINUX || defined ZS_HAVE_OSX || defined ZS_HAVE_OPENVMS
+#include <pthread.h>
+#elif defined ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#else
+#include <semaphore.h>
+#endif
+
+namespace zs
+{
+
+    //  Simple semaphore. Only single thread may be waiting at any given time.
+    //  Also, the semaphore may not be posted before the previous post
+    //  was matched by corresponding wait and the waiting thread was
+    //  released.
+
+#if defined ZS_HAVE_LINUX || defined ZS_HAVE_OSX || defined ZS_HAVE_OPENVMS
+
+    //  On platforms that allow for double locking of a mutex from the same
+    //  thread, simple semaphore is implemented using mutex, as it is more
+    //  efficient than full-blown semaphore.
+
+    class simple_semaphore_t
+    { 
+    public:
+
+        //  Initialise the semaphore.
+        inline simple_semaphore_t ()
+        {
+            int rc = pthread_mutex_init (&mutex, NULL);
+	    errno_assert (rc == 0);
+            rc = pthread_mutex_lock (&mutex);
+	    errno_assert (rc == 0);
+        }
+
+        //  Destroy the semaphore.
+        inline ~simple_semaphore_t ()
+        {
+            int rc = pthread_mutex_unlock (&mutex);
+            errno_assert (rc == 0);
+            rc = pthread_mutex_destroy (&mutex);
+            errno_assert (rc == 0);
+        }
+
+        //  Wait for the semaphore.
+        inline void wait ()
+        {
+             int rc = pthread_mutex_lock (&mutex);
+             errno_assert (rc == 0);
+        }
+
+        //  Post the semaphore.
+        inline void post ()
+        {
+            int rc = pthread_mutex_unlock (&mutex);
+            errno_assert (rc == 0);
+        }
+
+    private:
+
+        pthread_mutex_t mutex;
+
+        //  Disable copying of the object.
+        simple_semaphore_t (const simple_semaphore_t&);
+        void operator = (const simple_semaphore_t&);
+    };
+
+#elif defined ZMQ_HAVE_WINDOWS
+
+    //  On Windows platform simple semaphore is implemeted using event object.
+
+    class simple_semaphore_t
+    { 
+    public:
+
+        //  Initialise the semaphore.
+        inline simple_semaphore_t ()
+        {
+            ev = CreateEvent (NULL, FALSE, FALSE, NULL);
+            win_assert (ev != NULL);
+        }
+
+        //  Destroy the semaphore.
+        inline ~simple_semaphore_t ()
+        {
+            int rc = CloseHandle (ev);
+            win_assert (rc != 0);    
+        }
+
+        //  Wait for the semaphore.
+        inline void wait ()
+        {
+            DWORD rc = WaitForSingleObject (ev, INFINITE);
+            win_assert (rc != WAIT_FAILED);
+        }
+
+        //  Post the semaphore.
+        inline void post ()
+        {
+            int rc = SetEvent (ev);
+            win_assert (rc != 0);
+        }
+
+    private:
+
+        HANDLE ev;
+
+        //  Disable copying of the object.
+        simple_semaphore_t (const simple_semaphore_t&);
+        void operator = (const simple_semaphore_t&);
+    };
+
+#else
+
+    //  Default implementation maps simple semaphore to standard semaphore.
+
+    class simple_semaphore_t
+    { 
+    public:
+
+        //  Initialise the semaphore.
+        inline simple_semaphore_t ()
+        {
+             int rc = sem_init (&sem, 0, 0);
+             errno_assert (rc != -1);
+        }
+
+        //  Destroy the semaphore.
+        inline ~simple_semaphore_t ()
+        {
+             int rc = sem_destroy (&sem);
+             errno_assert (rc != -1);
+        }
+
+        //  Wait for the semaphore.
+        inline void wait ()
+        {
+             int rc = sem_wait (&sem);
+             errno_assert (rc != -1);
+        }
+
+        //  Post the semaphore.
+        inline void post ()
+        {
+            int rc = sem_post (&sem);
+            errno_assert (rc != -1);
+        }
+
+    private:
+
+        //  Underlying system semaphore object.
+        sem_t sem;
+
+        //  Disable copying of the object.
+        simple_semaphore_t (const simple_semaphore_t&);
+        void operator = (const simple_semaphore_t&);
+    };
+
+#endif
+
+}
+
+#endif
diff --git a/src/socket_base.cpp b/src/socket_base.cpp
new file mode 100644
index 0000000..07606ad
--- /dev/null
+++ b/src/socket_base.cpp
@@ -0,0 +1,267 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string>
+
+#include "../include/zs.h"
+
+#include "socket_base.hpp"
+#include "app_thread.hpp"
+#include "err.hpp"
+#include "listener.hpp"
+#include "connecter.hpp"
+#include "simple_semaphore.hpp"
+#include "io_thread.hpp"
+#include "io_object.hpp"
+#include "session.hpp"
+#include "dummy_aggregator.hpp"
+#include "dummy_distributor.hpp"
+
+zs::socket_base_t::socket_base_t (app_thread_t *thread_, session_t *session_) :
+    object_t (thread_),
+    thread (thread_),
+    session (session_),
+    has_in (true),
+    has_out (true)
+{
+    session->set_engine (this);
+}
+
+void zs::socket_base_t::shutdown ()
+{
+    //  Destroy all the I/O objects created from this socket.
+    for (io_objects_t::size_type i = 0; i != io_objects.size (); i++)
+        io_objects [i]->shutdown ();
+
+    delete this;
+}
+
+void zs::socket_base_t::schedule_terminate ()
+{
+    //  Terminate is never scheduled on socket engines.
+    zs_assert (false);
+}
+
+void zs::socket_base_t::terminate ()
+{
+    //  Destroy all the I/O objects created from this socket.
+    //  First unregister the object from I/O thread, then terminate it in
+    //  this application thread.
+    simple_semaphore_t smph;
+    for (io_objects_t::size_type i = 0; i != io_objects.size (); i++) {
+        send_unreg (io_objects [i], &smph);
+        smph.wait ();
+        io_objects [i]->terminate ();
+    }
+
+    zs_assert (session);
+    session->disconnected ();
+
+    delete this;
+}
+
+zs::socket_base_t::~socket_base_t ()
+{
+}
+
+void zs::socket_base_t::disable_in ()
+{
+    has_in = false;
+}
+
+void zs::socket_base_t::disable_out ()
+{
+    has_out = false;
+}
+
+int zs::socket_base_t::bind (const char *addr_, zs_opts *opts_)
+{
+    thread->process_commands (false);
+
+    std::string addr (addr_);
+    std::string::size_type pos = addr.find ("://");
+    if (pos == std::string::npos || addr.substr (0, pos) == "zmq.tcp") {
+
+        //  Choose the I/O thread with the least load, create the listener.
+        //  Note that same taskset is used to choose the I/O thread to handle
+        //  the listening socket and newly created connections.
+        //  Note that has_in and has_out are twisted at this place - listener
+        //  is going to create peer objects, so the message flows are viewed
+        //  from the opposite direction.
+        io_thread_t *io_thread = choose_io_thread (opts_ ? opts_->taskset : 0);
+        listener_t *listener = new listener_t (io_thread, addr_, session,
+            has_out, has_in, opts_ ? opts_->taskset : 0);
+
+        //  Ask it to start interacting with the I/O thread.
+        simple_semaphore_t smph;
+        send_reg (listener, &smph);
+
+        //  Store the reference to the listener so that it can be terminated
+        //  when the socket is closed.
+        io_objects.push_back (listener);
+
+        //  Wait while listener is actually registered with the I/O thread.
+        smph.wait ();
+
+        return 0;
+    }
+    else if (addr.substr (0, pos) == "inproc") {
+
+        //  For inproc transport the only thing we have to do is to register
+        //  this socket as an inproc endpoint with the supplied name.
+        return register_inproc_endpoint (addr.substr (pos + 3).c_str (),
+            session);
+    }
+    else {
+
+        //  Unknown protocol requested.
+        errno = EINVAL;
+        return -1;
+    }
+}
+
+int zs::socket_base_t::connect (const char *addr_, zs_opts *opts_)
+{
+    thread->process_commands (false);
+
+    std::string addr (addr_);
+    std::string::size_type pos = addr.find ("://");
+    if (pos == std::string::npos || addr.substr (0, pos) == "zmq.tcp") {
+
+        //  Choose the I/O thread with the least load, create the connecter and
+        //  session.
+        io_thread_t *io_thread = choose_io_thread (opts_ ? opts_->taskset : 0);
+        i_mux *mux = new dummy_aggregator_t;
+        zs_assert (mux);
+        i_demux *demux = new dummy_distributor_t;
+        zs_assert (demux);
+        session_t *peer = new session_t (io_thread, io_thread, mux, demux,
+            false, true);
+        zs_assert (peer);
+        connecter_t *connecter = new connecter_t (io_thread, addr_, peer);
+        zs_assert (connecter);
+
+        //  Increment session's command sequence number so that it won't get
+        //  deallocated till the subsequent bind command arrives.
+        peer->inc_seqnum ();
+
+        //  Register the connecter (and session) with its I/O thread.
+        simple_semaphore_t smph;
+        send_reg (connecter, &smph);
+
+        //  Store the reference to the connecter so that it can be terminated
+        //  when the socket is closed.
+        io_objects.push_back (connecter);
+
+        //  Wait till registration succeeds.
+        smph.wait ();
+
+        //  Bind local session with the connecter's session so that messages
+        //  can flow in both directions.
+        session->bind (peer, has_in, has_out);
+
+        return 0;
+    }
+    else if (addr.substr (0, pos) == "inproc") {
+
+        //  Get the MD responsible for the address. In case of invalid address
+        //  return error.
+        object_t *peer = get_inproc_endpoint (addr.substr (pos + 3).c_str ());
+        if (!peer) {
+            errno = EADDRNOTAVAIL;
+            return -1;
+        }
+
+        //  Create bidirectional message pipes between this session and
+        //  the peer session.
+        session->bind (peer, has_in, has_out);
+
+        return 0;
+    }
+    else {
+
+        //  Unknown protocol requested.
+        errno = EINVAL;
+        return -1;
+    }
+}
+
+int zs::socket_base_t::subscribe (const char *criteria_)
+{
+    //  No implementation at the moment...
+    errno = ENOTSUP;
+    return -1;
+}
+
+int zs::socket_base_t::send (zs_msg *msg_, int flags_)
+{
+    thread->process_commands (false);
+    while (true) {
+        if (session->write (msg_))
+            return 0;
+        if (flags_ & ZS_NOBLOCK) {
+            errno = EAGAIN;
+            return -1;
+        }
+        thread->process_commands (true);
+    }
+}
+
+int zs::socket_base_t::flush ()
+{
+    thread->process_commands (false);
+    session->flush ();
+    return 0;
+}
+
+int zs::socket_base_t::recv (zs_msg *msg_, int flags_)
+{
+    thread->process_commands (false);
+    while (true) {
+        if (session->read (msg_))
+            return 0;
+        if (flags_ & ZS_NOBLOCK) {
+            errno = EAGAIN;
+            return -1;
+        }
+        thread->process_commands (true);
+    }
+}
+
+int zs::socket_base_t::close ()
+{
+    terminate ();
+    return 0;
+}
+
+void zs::socket_base_t::attach (struct i_poller *poller_, i_session *session_)
+{
+    zs_assert (false);
+}
+
+void zs::socket_base_t::detach ()
+{
+    zs_assert (false);
+}
+
+void zs::socket_base_t::revive ()
+{
+    //  We can ignore the event safely here.
+}
+
diff --git a/src/socket_base.hpp b/src/socket_base.hpp
new file mode 100644
index 0000000..ed0272a
--- /dev/null
+++ b/src/socket_base.hpp
@@ -0,0 +1,96 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SOCKET_BASE_HPP_INCLUDED__
+#define __ZS_SOCKET_BASE_HPP_INCLUDED__
+
+#include <vector>
+
+#include "i_engine.hpp"
+#include "i_api.hpp"
+#include "object.hpp"
+
+namespace zs
+{
+
+    class socket_base_t : public object_t, public i_engine, public i_api
+    {
+    public:
+
+        //  TODO: Possibly, session can be attached to the engine using
+        //  attach function.
+        socket_base_t (class app_thread_t *thread_, class session_t *session_);
+
+        //  i_engine interface implementation.
+        void attach (struct i_poller *poller_, struct i_session *session_);
+        void detach ();
+        void revive ();
+        void schedule_terminate ();
+        void terminate ();
+        void shutdown ();
+
+        // i_api interface implementation.
+        int bind (const char *addr_, struct zs_opts *opts_);
+        int connect (const char *addr_, struct zs_opts *opts_);
+        int subscribe (const char *criteria_);
+        int send (struct zs_msg *msg_, int flags_);
+        int flush ();
+        int recv (struct zs_msg *msg_, int flags_);
+        int close ();
+
+    protected:
+
+        //  Clean-up. The function has to be protected rather than private,
+        //  otherwise auto-generated destructor in derived classes
+        //  cannot be compiled. It has to be virtual so that socket_base_t's
+        //  terminate & shutdown functions deallocate correct type of object.
+        virtual ~socket_base_t ();
+
+        //  By default, socket is able to pass messages in both inward and
+        //  outward directions. By calling these functions, particular
+        //  socket type is able to eliminate one direction.
+        void disable_in ();
+        void disable_out ();
+
+    private:
+
+        //  Pointer to the application thread the socket belongs to.
+        class app_thread_t *thread;
+
+        //  Pointer to the associated session object.
+        class session_t *session;
+
+        //  List of I/O object created via this socket. These have to be shut
+        //  down when the socket is closed.
+        typedef std::vector <class io_object_t*> io_objects_t;
+        io_objects_t io_objects;
+
+        //  If true, socket creates inbound pipe when binding to an engine.
+        bool has_in;
+
+        //  If true, socket creates outbound pipe when binding to an engine.
+        bool has_out;
+
+        socket_base_t (const socket_base_t&);
+        void operator = (const socket_base_t&);
+    };
+
+}
+
+#endif
diff --git a/src/stdint.hpp b/src/stdint.hpp
new file mode 100644
index 0000000..b4c6125
--- /dev/null
+++ b/src/stdint.hpp
@@ -0,0 +1,70 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_STDINT_HPP_INCLUDED__
+#define __ZS_STDINT_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_SOLARIS
+
+#include <inttypes.h>
+
+#elif defined _MSC_VER
+
+#ifndef int8_t
+typedef __int8 int8_t;
+#endif
+#ifndef int16_t
+typedef __int16 int16_t;
+#endif
+#ifndef int32_t
+typedef __int32 int32_t;
+#endif
+#ifndef int64_t
+typedef __int64 int64_t;
+#endif
+#ifndef uint8_t
+typedef unsigned __int8 uint8_t;
+#endif
+#ifndef uint16_t
+typedef unsigned __int16 uint16_t;
+#endif
+#ifndef uint32_t
+typedef unsigned __int32 uint32_t;
+#endif
+#ifndef uint64_t
+typedef unsigned __int64 uint64_t;
+#endif
+
+#elif defined ZMQ_HAVE_OPENVMS
+
+#include <types.h>
+typedef unsigned __int8 uint8_t;
+typedef unsigned __int16 uint16_t;
+typedef unsigned __int32 uint32_t;
+typedef unsigned __int64 uint64_t;
+
+#else
+
+#include <stdint.h>
+
+#endif
+
+#endif
diff --git a/src/sub.cpp b/src/sub.cpp
new file mode 100644
index 0000000..59e838a
--- /dev/null
+++ b/src/sub.cpp
@@ -0,0 +1,45 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include "sub.hpp"
+#include "app_thread.hpp"
+#include "session.hpp"
+#include "err.hpp"
+
+zs::sub_t::sub_t (app_thread_t *thread_, session_t *session_) :
+    socket_base_t (thread_, session_)
+{
+    disable_out ();
+}
+
+int zs::sub_t::send (struct zs_msg *msg_, int flags_)
+{
+    //  Subscriber socket has no send function.
+    errno = ENOTSUP;
+    return -1;
+}
+
+int zs::sub_t::flush ()
+{
+    //  Subscriber socket has no flush function.
+    errno = ENOTSUP;
+    return -1;
+}
diff --git a/src/sub.hpp b/src/sub.hpp
new file mode 100644
index 0000000..b7c2bd2
--- /dev/null
+++ b/src/sub.hpp
@@ -0,0 +1,46 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_SUB_HPP_INCLUDED__
+#define __ZS_SUB_HPP_INCLUDED__
+
+#include "socket_base.hpp"
+
+namespace zs
+{
+
+    class sub_t : public socket_base_t
+    {
+    public:
+
+        sub_t (class app_thread_t *thread_, class session_t *session_);
+
+        //  i_api overloads.
+        int send (struct zs_msg *msg_, int flags_);
+        int flush ();
+
+    private:
+
+        sub_t (const sub_t&);
+        void operator = (const sub_t&);
+    };
+
+}
+
+#endif
diff --git a/src/tcp_connecter.cpp b/src/tcp_connecter.cpp
new file mode 100644
index 0000000..6b59290
--- /dev/null
+++ b/src/tcp_connecter.cpp
@@ -0,0 +1,138 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "tcp_connecter.hpp"
+#include "platform.hpp"
+#include "ip.hpp"
+#include "err.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+
+#include "windows.hpp"
+#error
+
+#else
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/tcp.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <fcntl.h>
+
+zs::tcp_connecter_t::tcp_connecter_t () :
+    s (retired_fd)
+{
+}
+
+zs::tcp_connecter_t::~tcp_connecter_t ()
+{
+    if (s != retired_fd)
+        close ();
+}
+
+int zs::tcp_connecter_t::open (const char *addr_)
+{
+    zs_assert (s == retired_fd);
+
+    //  Convert the hostname into sockaddr_in structure.
+    sockaddr_in address;
+    int rc = resolve_ip_hostname (&address, addr_);
+    if (rc != 0)
+        return -1;
+
+    //  Create the socket.
+    s = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
+    if (s == -1)
+        return -1;
+
+    // Set to non-blocking mode.
+    int flags = fcntl (s, F_GETFL, 0);
+    if (flags == -1) 
+        flags = 0;
+    rc = fcntl (s, F_SETFL, flags | O_NONBLOCK);
+    errno_assert (rc != -1);
+
+    //  Disable Nagle's algorithm.
+    int flag = 1;
+    rc = setsockopt (s, IPPROTO_TCP, TCP_NODELAY, (char*) &flag, sizeof (int));
+    errno_assert (rc == 0);
+
+#ifdef ZS_HAVE_OPENVMS
+    //  Disable delayed acknowledgements.
+    flag = 1;
+    rc = setsockopt (s, IPPROTO_TCP, TCP_NODELACK, (char*) &flag, sizeof (int));
+    errno_assert (rc != SOCKET_ERROR);
+#endif
+
+    //  Connect to the remote peer.
+    rc = ::connect (s, (sockaddr*) &address, sizeof address);
+
+    //  Connect was successfull immediately.
+    if (rc == 0)
+        return 0;
+
+    //  Asynchronous connect was launched.
+    if (rc == -1 && errno == EINPROGRESS)
+        return 1;
+
+    //  Error occured.
+    int err = errno;
+    close ();
+    errno = err;
+    return -1;
+}
+
+int zs::tcp_connecter_t::close ()
+{
+    zs_assert (s != retired_fd);
+    int rc = ::close (s);
+    if (rc != 0)
+        return -1;
+    s = retired_fd;
+    return 0;
+}
+
+zs::fd_t zs::tcp_connecter_t::get_fd ()
+{
+    return s;
+}
+
+zs::fd_t zs::tcp_connecter_t::connect ()
+{
+    //  Following code should handle both Berkeley-derived socket
+    //  implementations and Solaris.
+    int err = 0;
+    socklen_t len = sizeof err;
+    int rc = getsockopt (s, SOL_SOCKET, SO_ERROR, (char*) &err, &len);
+    if (rc == -1)
+        err = errno;
+    if (err != 0) {
+        close ();
+        errno = err;
+        return retired_fd;
+    }
+
+    fd_t result = s;
+    s = retired_fd;
+    return result;
+}
+
+#endif
diff --git a/src/tcp_connecter.hpp b/src/tcp_connecter.hpp
new file mode 100644
index 0000000..ef11242
--- /dev/null
+++ b/src/tcp_connecter.hpp
@@ -0,0 +1,65 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_TCP_CONNECTER_HPP_INCLUDED__
+#define __ZS_TCP_CONNECTER_HPP_INCLUDED__
+
+#include "fd.hpp"
+
+namespace zs
+{
+
+    //  The class encapsulating simple TCP listening socket.
+
+    class tcp_connecter_t
+    {
+    public:
+
+        tcp_connecter_t ();
+        ~tcp_connecter_t ();
+
+        //  Open TCP connecting socket. Address is in
+        //  <hostname>:<port-number> format. Returns -1 in case of error,
+        //  0 if connect was successfull immediately and 1 if async connect
+        //  was launched.
+        int open (const char *addr_);
+
+        //  Close the connecting socket.
+        int close ();
+
+        //  Get the file descriptor to poll on to get notified about
+        //  connection success.
+        fd_t get_fd ();
+
+        //  Get the file descriptor of newly created connection. Returns
+        //  retired_fd if the connection was unsuccessfull.
+        fd_t connect ();
+
+    private:
+
+        //  Underlying socket.
+        fd_t s;
+
+        tcp_connecter_t (const tcp_connecter_t&);
+        void operator = (const tcp_connecter_t&);
+    };
+
+}
+
+#endif
diff --git a/src/tcp_listener.cpp b/src/tcp_listener.cpp
new file mode 100644
index 0000000..3703950
--- /dev/null
+++ b/src/tcp_listener.cpp
@@ -0,0 +1,165 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "tcp_listener.hpp"
+#include "platform.hpp"
+#include "ip.hpp"
+#include "config.hpp"
+#include "err.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+
+#include "windows.hpp"
+#error
+
+#else
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/tcp.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <fcntl.h>
+
+zs::tcp_listener_t::tcp_listener_t () :
+    s (retired_fd)
+{
+}
+
+zs::tcp_listener_t::~tcp_listener_t ()
+{
+    if (s != retired_fd)
+        close ();
+}
+
+int zs::tcp_listener_t::open (const char *addr_)
+{
+    //  Convert the interface into sockaddr_in structure.
+    sockaddr_in ip_address;
+    int rc = resolve_ip_interface (&ip_address, addr_);
+    if (rc != 0)
+        return -1;
+    
+    //  Create a listening socket.
+    s = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
+    if (s == -1)
+        return -1;
+
+    //  Allow reusing of the address.
+    int flag = 1;
+    rc = setsockopt (s, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof (int));
+    errno_assert (rc == 0);
+
+    //  Set the non-blocking flag.
+    flag = fcntl (s, F_GETFL, 0);
+    if (flag == -1) 
+        flag = 0;
+    rc = fcntl (s, F_SETFL, flag | O_NONBLOCK);
+    errno_assert (rc != -1);
+
+    //  Bind the socket to the network interface and port.
+    rc = bind (s, (struct sockaddr*) &ip_address, sizeof (ip_address));
+    if (rc != 0) {
+        close ();
+        return -1;
+    }
+              
+    //  Listen for incomming connections.
+    rc = listen (s, tcp_connection_backlog);
+    if (rc != 0) {
+        close ();
+        return -1;
+    }
+
+    return 0;
+}
+
+int zs::tcp_listener_t::close ()
+{
+    zs_assert (s != retired_fd);
+    int rc = ::close (s);
+    if (rc != 0)
+        return -1;
+    s = retired_fd;
+    return 0;
+}
+
+zs::fd_t zs::tcp_listener_t::get_fd ()
+{
+    return s;
+}
+
+zs::fd_t zs::tcp_listener_t::accept ()
+{
+    zs_assert (s != retired_fd);
+
+    //  Accept one incoming connection.
+    fd_t sock = ::accept (s, NULL, NULL);
+
+#if (defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_FREEBSD || \
+     defined ZMQ_HAVE_OPENBSD || defined ZMQ_HAVE_OSX || \
+     defined ZMQ_HAVE_OPENVMS)
+    if (sock == -1 && 
+        (errno == EAGAIN || errno == EWOULDBLOCK || 
+         errno == EINTR || errno == ECONNABORTED))
+        return retired_fd;
+#elif (defined ZMQ_HAVE_SOLARIS || defined ZMQ_HAVE_AIX)
+    if (sock == -1 && 
+        (errno == EWOULDBLOCK || errno == EINTR || 
+         errno == ECONNABORTED || errno == EPROTO))
+        return retired_fd;
+#elif defined ZMQ_HAVE_HPUX
+    if (sock == -1 && 
+        (errno == EAGAIN || errno == EWOULDBLOCK || 
+         errno == EINTR || errno == ECONNABORTED || errno == ENOBUFS))
+        return retired_fd;
+#elif defined ZMQ_HAVE_QNXNTO 
+    if (sock == -1 && 
+        (errno == EWOULDBLOCK || errno == EINTR || errno == ECONNABORTED))
+        return retired_fd;
+#endif
+
+    errno_assert (sock != -1); 
+
+    // Set to non-blocking mode.
+    int flags = fcntl (s, F_GETFL, 0);
+    if (flags == -1) 
+        flags = 0;
+    int rc = fcntl (sock, F_SETFL, flags | O_NONBLOCK);
+    errno_assert (rc != -1);
+
+    //  Disable Nagle's algorithm.
+    int flag = 1;
+    rc = setsockopt (sock, IPPROTO_TCP, TCP_NODELAY, (char*) &flag,
+        sizeof (int));
+    errno_assert (rc == 0);
+
+#ifdef ZS_HAVE_OPENVMS
+    //  Disable delayed acknowledgements.
+    flag = 1;
+    rc = setsockopt (sock, IPPROTO_TCP, TCP_NODELACK, (char*) &flag,
+        sizeof (int));
+    errno_assert (rc != SOCKET_ERROR);
+#endif
+
+    return sock;
+}
+
+#endif
diff --git a/src/tcp_listener.hpp b/src/tcp_listener.hpp
new file mode 100644
index 0000000..156195b
--- /dev/null
+++ b/src/tcp_listener.hpp
@@ -0,0 +1,65 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_TCP_LISTENER_HPP_INCLUDED__
+#define __ZS_TCP_LISTENER_HPP_INCLUDED__
+
+#include "fd.hpp"
+
+namespace zs
+{
+
+    //  The class encapsulating simple TCP listening socket.
+
+    class tcp_listener_t
+    {
+    public:
+
+        tcp_listener_t ();
+        ~tcp_listener_t ();
+
+        //  Open TCP listining socket. Address is in
+        //  <interface-name>:<port-number> format. Interface name may be '*'
+        //  to bind to all the interfaces.
+        int open (const char *addr_);
+
+        //  Close the listening socket.
+        int close ();
+
+        //  Get the file descriptor to poll on to get notified about
+        //  newly created connections.
+        fd_t get_fd ();
+
+        //  Accept the new connection. Returns the file descriptor of the
+        //  newly created connection. The function may return retired_fd
+        //  if the connection was dropped while waiting in the listen backlog.
+        fd_t accept ();
+
+    private:
+
+        //  Underlying socket.
+        fd_t s;
+
+        tcp_listener_t (const tcp_listener_t&);
+        void operator = (const tcp_listener_t&);
+    };
+
+}
+
+#endif
diff --git a/src/tcp_socket.cpp b/src/tcp_socket.cpp
new file mode 100644
index 0000000..70fde96
--- /dev/null
+++ b/src/tcp_socket.cpp
@@ -0,0 +1,116 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "tcp_socket.hpp"
+#include "platform.hpp"
+#include "err.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+
+#include "windows.hpp"
+#error
+
+#else
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/tcp.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <fcntl.h>
+
+zs::tcp_socket_t::tcp_socket_t () :
+    s (retired_fd)
+{
+}
+
+zs::tcp_socket_t::~tcp_socket_t ()
+{
+    if (s != retired_fd)
+        close ();
+}
+
+int zs::tcp_socket_t::open (fd_t fd_)
+{
+    assert (s == retired_fd);
+    s = fd_;
+    return 0;
+}
+
+int zs::tcp_socket_t::close ()
+{
+    zs_assert (s != retired_fd);
+    int rc = ::close (s);
+    if (rc != 0)
+        return -1;
+    s = retired_fd;
+    return 0;
+}
+
+zs::fd_t zs::tcp_socket_t::get_fd ()
+{
+    return s;
+}
+
+int zs::tcp_socket_t::write (const void *data, int size)
+{
+    ssize_t nbytes = send (s, data, size, 0);
+
+    //  Several errors are OK. When speculative write is being done we may not
+    //  be able to write a single byte to the socket. Also, SIGSTOP issued
+    //  by a debugging tool can result in EINTR error.
+    if (nbytes == -1 && (errno == EAGAIN || errno == EWOULDBLOCK ||
+          errno == EINTR))
+        return 0;
+
+    //  Signalise peer failure.
+    if (nbytes == -1 && errno == ECONNRESET)
+        return -1;
+
+    errno_assert (nbytes != -1);
+    return (size_t) nbytes;
+}
+
+int zs::tcp_socket_t::read (void *data, int size)
+{
+    ssize_t nbytes = recv (s, data, size, 0);
+
+    //  Several errors are OK. When speculative read is being done we may not
+    //  be able to read a single byte to the socket. Also, SIGSTOP issued
+    //  by a debugging tool can result in EINTR error.
+    if (nbytes == -1 && (errno == EAGAIN || errno == EWOULDBLOCK ||
+          errno == EINTR))
+        return 0;
+
+    //  Signalise peer failure.
+    if (nbytes == -1 && (errno == ECONNRESET || errno == ECONNREFUSED))
+        return -1;
+
+    errno_assert (nbytes != -1);
+
+    //  Orderly shutdown by the other peer.
+    if (nbytes == 0)
+        return -1;
+
+    return (size_t) nbytes;
+}
+
+#endif
+
diff --git a/src/tcp_socket.hpp b/src/tcp_socket.hpp
new file mode 100644
index 0000000..a6c61ac
--- /dev/null
+++ b/src/tcp_socket.hpp
@@ -0,0 +1,70 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_TCP_SOCKET_HPP_INCLUDED__
+#define __ZS_TCP_SOCKET_HPP_INCLUDED__
+
+#include "fd.hpp"
+
+namespace zs
+{
+
+    //  The class encapsulating simple TCP read/write socket.
+
+    class tcp_socket_t
+    {
+    public:
+
+        tcp_socket_t ();
+        ~tcp_socket_t ();
+
+        //  Associates a socket with a native socket descriptor.
+        int open (fd_t fd_);
+         
+        //  Closes the underlying socket.
+        int close ();
+
+        //  Returns the underlying socket. Returns retired_fd when the socket
+        //  is in the closed state.
+        fd_t get_fd ();
+
+        //  Writes data to the socket. Returns the number of bytes actually
+        //  written (even zero is to be considered to be a success). In case
+        //  of error or orderly shutdown by the other peer -1 is returned.
+        int write (const void *data, int size);
+
+        //  Reads data from the socket (up to 'size' bytes). Returns the number
+        //  of bytes actually read (even zero is to be considered to be
+        //  a success). In case of error or orderly shutdown by the other
+        //  peer -1 is returned.
+        int read (void *data, int size);
+
+    private:
+
+        //  Underlying socket.
+        fd_t s;
+
+        //  Disable copy construction of tcp_socket.
+        tcp_socket_t (const tcp_socket_t&);
+        void operator = (const tcp_socket_t&);
+    };
+
+}
+
+#endif
diff --git a/src/thread.cpp b/src/thread.cpp
new file mode 100644
index 0000000..7cf54f2
--- /dev/null
+++ b/src/thread.cpp
@@ -0,0 +1,88 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "thread.hpp"
+#include "err.hpp"
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+
+void zs::thread_t::start (thread_fn *tfn_, void *arg_)
+{
+    tfn = tfn_;
+    arg =arg_;
+    descriptor = (HANDLE) _beginthreadex (NULL, 0,
+        &zmq::thread_t::thread_routine, this, 0 , NULL);
+    win_assert (descriptor != NULL);    
+}
+
+void zs::thread_t::stop ()
+{
+    DWORD rc = WaitForSingleObject (descriptor, INFINITE);
+    win_assert (rc != WAIT_FAILED);
+}
+
+unsigned int __stdcall zs::thread_t::thread_routine (void *arg_)
+{
+    thread_t *self = (thread_t*) arg_;
+    self->tfn (self->arg);
+    return 0;
+}
+
+#else
+
+#include <signal.h>
+
+void zs::thread_t::start (thread_fn *tfn_, void *arg_)
+{
+    tfn = tfn_;
+    arg =arg_;
+    int rc = pthread_create (&descriptor, NULL, thread_routine, this);
+    errno_assert (rc == 0);
+}
+
+void zs::thread_t::stop ()
+{
+    int rc = pthread_join (descriptor, NULL);
+    errno_assert (rc == 0);
+}
+
+void *zs::thread_t::thread_routine (void *arg_)
+{
+#if !defined ZMQ_HAVE_OPENVMS
+    //  Following code will guarantee more predictable latecnies as it'll
+    //  disallow any signal handling in the I/O thread.
+    sigset_t signal_set;
+    int rc = sigfillset (&signal_set);
+    errno_assert (rc == 0);
+    rc = pthread_sigmask (SIG_BLOCK, &signal_set, NULL);
+    errno_assert (rc == 0);
+#endif
+
+    thread_t *self = (thread_t*) arg_;   
+    self->tfn (self->arg);
+    return NULL;
+}
+
+#endif
+
+
+
+
+
diff --git a/src/thread.hpp b/src/thread.hpp
new file mode 100644
index 0000000..6ee9194
--- /dev/null
+++ b/src/thread.hpp
@@ -0,0 +1,77 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_THREAD_HPP_INCLUDED__
+#define __ZS_THREAD_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#ifdef ZS_HAVE_WINDOWS
+#include "windows.hpp"
+#else
+#include <pthread.h>
+#endif
+
+namespace zs
+{
+
+    typedef void (thread_fn) (void*);
+
+    //  Class encapsulating OS thread. Thread initiation/termination is done
+    //  using special functions rather than in constructor/destructor so that
+    //  thread isn't created during object construction by accident, causing
+    //  newly created thread to access half-initialised object. Same applies
+    //  to the destruction process: Thread should be terminated before object
+    //  destruction begins, otherwise it can access half-destructed object.
+
+    class thread_t
+    {
+    public:
+
+        inline thread_t ()
+        {
+        }
+
+        //  Creates OS thread. 'tfn' is main thread function. It'll be passed
+        //  'arg' as an argument.
+        void start (thread_fn *tfn_, void *arg_);
+
+        //  Waits for thread termination.
+        void stop ();
+
+    private:
+
+#ifdef ZS_HAVE_WINDOWS
+        static unsigned int __stdcall thread_routine (void *arg_);
+        HANDLE descriptor;
+#else
+        static void *thread_routine (void *arg_);
+        pthread_t descriptor;
+#endif
+
+        thread_fn *tfn;
+        void *arg;
+
+        thread_t (const thread_t&);
+        void operator = (const thread_t&);
+    };
+
+}
+
+#endif
diff --git a/src/uuid.cpp b/src/uuid.cpp
new file mode 100644
index 0000000..d9883cd
--- /dev/null
+++ b/src/uuid.cpp
@@ -0,0 +1,136 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+#include "uuid.hpp"
+#include "err.hpp"
+
+#if defined ZS_HAVE_WINDOWS
+
+#include <rpcdce.h>
+
+zs::uuid_t::uuid_t ()
+{
+    RPC_STATUS ret = UuidCreate (&uuid);
+    zs_assert (ret == RPC_S_OK);
+    ret = UuidToString (&uuid, &uuid_str);
+    zs_assert (ret == RPC_S_OK);
+}
+
+zs::uuid_t::~uuid_t ()
+{
+    RPC_STATUS ret = RpcStringFree(&uuid_str);
+    assert (ret == RPC_S_OK);
+}
+
+const char *zs::uuid_t::to_string ()
+{
+    return uuid_str;
+}
+
+#elif defined ZS_HAVE_FREEBSD
+
+#include <stdlib.h>
+#include <uuid.h>
+
+zs::uuid_t::uuid_t ()
+{
+    uint32_t status;
+    uuid_create (&uuid, &status);
+    zs_assert (status == uuid_s_ok);
+    uuid_to_string (&uuid, &uuid_str, &status);
+    zs_assert (status == uuid_s_ok);
+}
+
+zs::uuid_t::~uuid_t ()
+{
+    free (uuid_str);
+}
+
+const char *zs::uuid_t::to_string ()
+{
+    return uuid_str;
+}
+
+#elif defined ZS_HAVE_LINUX || defined ZS_HAVE_SOLARIS || defined ZS_HAVE_OSX
+
+#include <uuid/uuid.h>
+
+zs::uuid_t::uuid_t ()
+{
+    uuid_generate (uuid);
+    uuid_unparse (uuid, uuid_buf);
+}
+
+zs::uuid_t::~uuid_t ()
+{
+}
+
+const char *zs::uuid_t::to_string ()
+{
+    return uuid_buf;
+}
+
+#else
+
+#include <stdio.h>
+#include <string.h>
+#include <openssl/rand.h>
+
+zs::uuid_t::uuid_t ()
+{
+    unsigned char rand_buf [16];
+    int ret = RAND_bytes (rand_buf, sizeof rand_buf);
+    zs_assert (ret == 1);
+
+    //  Read in UUID fields.
+    memcpy (&time_low, rand_buf, sizeof time_low);
+    memcpy (&time_mid, rand_buf + 4, sizeof time_mid);
+    memcpy (&time_hi_and_version, rand_buf + 6, sizeof time_hi_and_version);
+    memcpy (&clock_seq_hi_and_reserved, rand_buf + 8,
+        sizeof clock_seq_hi_and_reserved);
+    memcpy (&clock_seq_low, rand_buf + 9, sizeof clock_seq_low);
+    memcpy (&node [0], rand_buf + 10, sizeof node);
+
+    //  Store UUID version number.
+    time_hi_and_version = (time_hi_and_version & 0x0fff) | 4 << 12;
+
+    //  Store UUID type.
+    clock_seq_hi_and_reserved = (clock_seq_hi_and_reserved & 0x3f) | 0x80;
+
+    snprintf (uuid_buf, sizeof uuid_buf,
+        "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+        time_low,
+        time_mid,
+        time_hi_and_version,
+        clock_seq_hi_and_reserved,
+        clock_seq_low,
+        node [0], node [1], node [2], node [3], node [4], node [5]);
+}
+
+zs::uuid_t::~uuid_t ()
+{
+}
+
+const char *zs::uuid_t::to_string ()
+{
+    return uuid_buf;
+}
+
+#endif
diff --git a/src/uuid.hpp b/src/uuid.hpp
new file mode 100644
index 0000000..94c3e8a
--- /dev/null
+++ b/src/uuid.hpp
@@ -0,0 +1,82 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_UUID_HPP_INCLUDED__
+#define __ZS_UUID_HPP_INCLUDED__
+
+#include "platform.hpp"
+
+#if defined ZS_HAVE_WINDOWS
+#include <rpcdce.h>
+#elif defined ZS_HAVE_FREEBSD
+#include <uuid.h>
+#elif defined ZS_HAVE_LINUX || defined ZS_HAVE_SOLARIS || defined ZS_HAVE_OSX
+#include <uuid/uuid.h>
+#else
+#include <stdint.h>
+#endif
+
+namespace zs
+{
+
+    //  This class provides RFC 4122 (a Universally Unique IDentifier)
+    //  implementation.
+
+    class uuid_t
+    {
+    public:
+
+        uuid_t ();
+        ~uuid_t ();
+
+        //  Returns a pointer to buffer containing the textual
+        //  representation of the UUID. The caller is reponsible to
+        //  free the allocated memory.
+        const char *to_string ();
+
+    private:
+
+        //  The length of textual representation of UUID.
+        enum { uuid_string_len = 36 };
+
+#if defined ZS_HAVE_WINDOWS
+        ::UUID uuid;
+        char *uuid_str;
+#elif defined ZS_HAVE_FREEBSD
+        ::uuid_t uuid;
+        char *uuid_str;
+#elif defined ZS_HAVE_LINUX || defined ZS_HAVE_SOLARIS || defined ZS_HAVE_OSX
+        ::uuid_t uuid;
+        char uuid_buf [uuid_string_len + 1];
+#else
+        //  RFC 4122 UUID's fields
+        uint32_t time_low;
+        uint16_t time_mid;
+        uint16_t time_hi_and_version;
+        uint8_t clock_seq_hi_and_reserved;
+        uint8_t clock_seq_low;
+        uint8_t node [6];
+
+        char uuid_buf [uuid_string_len + 1];
+#endif
+    };
+
+}
+
+#endif
diff --git a/src/windows.hpp b/src/windows.hpp
new file mode 100644
index 0000000..a4a89ba
--- /dev/null
+++ b/src/windows.hpp
@@ -0,0 +1,56 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_WINDOWS_HPP_INCLUDED__
+#define __ZS_WINDOWS_HPP_INCLUDED__
+
+// The purpose of this header file is to turn on only the items actually needed
+// on the windows platform.
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#ifndef NOUSER  //  No USER defines and routines.
+#define NOUSER
+#endif
+#ifndef NOMCX   //  No Modem Configuration Extensions.
+#define NOMCX
+#endif
+#ifndef NOIME   //  No Input Method Editor.
+#define NOIME
+#endif
+#ifndef NOSOUND //  No Sound driver routines.
+#define NOSOUND
+#endif
+
+#include <windows.h>
+
+//  Enable winsock (not included when WIN32_LEAN_AND_MEAN is defined).
+#if(_WIN32_WINNT >= 0x0400)
+#include <winsock2.h>
+#include <mswsock.h>
+#else
+#include <winsock.h>
+#endif
+
+#include <ws2tcpip.h>
+#include <ipexport.h>
+#include <process.h>
+
+#endif
diff --git a/src/wire.hpp b/src/wire.hpp
new file mode 100644
index 0000000..31ebef1
--- /dev/null
+++ b/src/wire.hpp
@@ -0,0 +1,98 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_WIRE_HPP_INCLUDED__
+#define __ZS_WIRE_HPP_INCLUDED__
+
+#include "stdint.hpp"
+
+namespace zs
+{
+
+    //  Helper functions to convert different integer types to/from network
+    //  byte order.
+
+    inline void put_uint8 (unsigned char *buffer_, uint8_t value)
+    {
+        *buffer_ = value;
+    }
+
+    inline uint8_t get_uint8 (unsigned char *buffer_)
+    {
+        return *buffer_;
+    }
+
+    inline void put_uint16 (unsigned char *buffer_, uint16_t value)
+    {
+        buffer_ [0] = (unsigned char) (((value) >> 8) & 0xff);
+        buffer_ [1] = (unsigned char) (value & 0xff);
+    }
+
+    inline uint16_t get_uint16 (unsigned char *buffer_)
+    {
+        return
+            (((uint16_t) buffer_ [0]) << 8) |
+            ((uint16_t) buffer_ [1]);
+    }
+
+    inline void put_uint32 (unsigned char *buffer_, uint32_t value)
+    {
+        buffer_ [0] = (unsigned char) (((value) >> 24) & 0xff);
+        buffer_ [1] = (unsigned char) (((value) >> 16) & 0xff);
+        buffer_ [2] = (unsigned char) (((value) >> 8) & 0xff);
+        buffer_ [3] = (unsigned char) (value & 0xff);
+    }
+
+    inline uint32_t get_uint32 (unsigned char *buffer_)
+    {
+        return
+            (((uint32_t) buffer_ [0]) << 24) |
+            (((uint32_t) buffer_ [1]) << 16) |
+            (((uint32_t) buffer_ [2]) << 8) |
+            ((uint32_t) buffer_ [3]);
+    }
+
+    inline void put_uint64 (unsigned char *buffer_, uint64_t value)
+    {
+        buffer_ [0] = (unsigned char) (((value) >> 56) & 0xff);
+        buffer_ [1] = (unsigned char) (((value) >> 48) & 0xff);
+        buffer_ [2] = (unsigned char) (((value) >> 40) & 0xff);
+        buffer_ [3] = (unsigned char) (((value) >> 32) & 0xff);
+        buffer_ [4] = (unsigned char) (((value) >> 24) & 0xff);
+        buffer_ [5] = (unsigned char) (((value) >> 16) & 0xff);
+        buffer_ [6] = (unsigned char) (((value) >> 8) & 0xff);
+        buffer_ [7] = (unsigned char) (value & 0xff);
+    }
+
+    inline uint64_t get_uint64 (unsigned char *buffer_)
+    {
+        return
+            (((uint64_t) buffer_ [0]) << 56) |
+            (((uint64_t) buffer_ [1]) << 48) |
+            (((uint64_t) buffer_ [2]) << 40) |
+            (((uint64_t) buffer_ [3]) << 32) |
+            (((uint64_t) buffer_ [4]) << 24) |
+            (((uint64_t) buffer_ [5]) << 16) |
+            (((uint64_t) buffer_ [6]) << 8) |
+            ((uint64_t) buffer_ [7]);
+    }
+
+}
+
+#endif
diff --git a/src/ypipe.hpp b/src/ypipe.hpp
new file mode 100644
index 0000000..5ffd5c9
--- /dev/null
+++ b/src/ypipe.hpp
@@ -0,0 +1,209 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_YPIPE_HPP_INCLUDED__
+#define __ZS_YPIPE_HPP_INCLUDED__
+
+#include "atomic_ptr.hpp"
+#include "yqueue.hpp"
+#include "platform.hpp"
+
+namespace zs
+{
+
+    //  Lock-free queue implementation.
+    //  Only a single thread can read from the pipe at any specific moment.
+    //  Only a single thread can write to the pipe at any specific moment.
+    //
+    //  T is the type of the object in the queue.
+    //  If the template parameter D is set to true, it is quaranteed that
+    //  the pipe will die in a finite time (so that you can swich to some
+    //  other task). If D is set to false, reading from the pipe may result
+    //  in an infinite cycle (if the pipe is continuosly fed by new elements).
+    //  N is granularity of the pipe (how many elements have to be inserted
+    //  till actual memory allocation is required).
+
+    template <typename T, bool D, int N> class ypipe_t
+    {
+    public:
+
+        //  Initialises the pipe. If 'dead' is set to true, the pipe is
+        //  created in dead state.
+        inline ypipe_t (bool dead_ = true) :
+            stop (false)
+        {
+            //  Insert terminator element into the queue.
+            queue.push ();
+
+            //  Let all the pointers to point to the terminator
+            //  (unless pipe is dead, in which case c is set to NULL).
+            r = w = &queue.back ();
+            c.set (dead_ ? NULL : &queue.back ());
+        }
+
+        //  Following function (write) deliberately copies uninitialised data
+        //  when used with zs_msg. Initialising the VSM body for
+        //  non-VSM messages won't be good for performance.
+
+#ifdef ZMQ_HAVE_OPENVMS
+#pragma message save
+#pragma message disable(UNINIT)
+#endif
+
+        //  Write an item to the pipe.  Don't flush it yet.
+        inline void write (const T &value_)
+        {
+            //  Place the value to the queue, add new terminator element.
+            queue.back () = value_;
+            queue.push ();
+        }
+
+#ifdef ZMQ_HAVE_OPENVMS
+#pragma message restore
+#endif
+
+        //  Flush the messages into the pipe. Returns false if the reader
+        //  thread is sleeping. In that case, caller is obliged to wake the
+        //  reader up before using the pipe again.
+        inline bool flush ()
+        {
+            //  If there are no un-flushed items, do nothing.
+            if (w == &queue.back ())
+                return true;
+
+            //  Try to set 'c' to 'back'
+            if (c.cas (w, &queue.back ()) != w) {
+
+                //  Compare-and-swap was unseccessful because 'c' is NULL.
+                //  This means that the reader is asleep. Therefore we don't
+                //  care about thread-safeness and update c in non-atomic
+                //  manner. We'll return false to let the caller know
+                //  that reader is sleeping.
+                c.set (&queue.back ());
+                w = &queue.back ();
+                return false;
+            }
+
+            //  Reader is alive. Nothing special to do now. Just move
+            //  the 'first un-flushed item' pointer to the end of the queue.
+            w = &queue.back ();
+            return true;
+        }
+
+        //  Reads an item from the pipe. Returns false if there is no value.
+        //  available.
+        inline bool read (T *value_)
+        {
+            //  Was the value was prefetched already? If so, return it.
+            if (&queue.front () != r) {
+                 *value_ = queue.front ();
+                 queue.pop ();
+                 return true;
+            }
+
+            //  There's no prefetched value, so let us prefetch more values.
+            //  (Note that D is a template parameter. Becaue of that one of
+            //  the following branches will be completely optimised away
+            //  by the compiler.)
+            if (D) {
+
+                //  If one prefetch was already done since last sleeping,
+                //  don't do a new one, rather ask caller to go asleep.
+                if (stop) {
+                    stop = false;
+                    return false;
+                }
+
+                //  Get new items. Perform the operation in atomic fashion.
+                r = c.xchg (NULL);
+
+                //  If there are no elements prefetched, exit and go asleep.
+                //  During pipe's lifetime r should never be NULL, however,
+                //  during pipe shutdown when retrieving messages from it
+                //  to deallocate them, this can happen.
+                if (&queue.front () == r || !r) {
+                    stop = false;
+                    return false;
+                }
+                else {
+
+                    //  We want to do only a single prefetch in D scenario
+                    //  before going asleep. Thus, we set stop variable to true
+                    //  so that we can return false next time the prefetch is
+                    //  attempted.
+                    stop = true;
+                }
+            }
+            else {
+
+                //  Prefetching in non-D scenario is to simply retrieve the
+                //  pointer from c in atomic fashion. If there are no
+                //  items to prefetch, set c to NULL (using compare-and-swap).
+                r = c.cas (&queue.front (), NULL);
+
+                //  If there are no elements prefetched, exit.
+                //  During pipe's lifetime r should never be NULL, however,
+                //  during pipe shutdown when retrieving messages from it
+                //  to deallocate them, this can happen.
+                if (&queue.front () == r || !r)
+                    return false;
+            }
+
+            //  There was at least one value prefetched -
+            //  return it to the caller.
+            *value_ = queue.front ();
+            queue.pop ();
+            return true;
+        }
+
+    protected:
+
+        //  Allocation-efficient queue to store pipe items.
+        //  Front of the queue points to the first prefetched item, back of
+        //  the pipe points to last un-flushed item. Front is used only by
+        //  reader thread, while back is used only by writer thread.
+        yqueue_t <T, N> queue;
+
+        //  Points to the first un-flushed item. This variable is used
+        //  exclusively by writer thread.
+        T *w;
+
+        //  Points to the first un-prefetched item. This variable is used
+        //  exclusively by reader thread.
+        T *r;
+
+        //  The single contention point of contention between writer and
+        //  reader thread. Points past the last flushed item. If it is NULL,
+        //  reader is asleep. This pointer should be always accessed using
+        //  atomic operations.
+        atomic_ptr_t <T> c;
+
+        //  Used only if 'D' template parameter is set to true. If true,
+        //  prefetch was already done since last sleeping and the reader
+        //  should go asleep instead of prefetching once more.
+        bool stop;
+
+        //  Disable copying of ypipe object.
+        ypipe_t (const ypipe_t&);
+        void operator = (const ypipe_t&);
+    };
+
+}
+
+#endif
diff --git a/src/ypollset.cpp b/src/ypollset.cpp
new file mode 100644
index 0000000..0be6791
--- /dev/null
+++ b/src/ypollset.cpp
@@ -0,0 +1,56 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "ypollset.hpp"
+
+zs::ypollset_t::ypollset_t ()
+{
+}
+
+void zs::ypollset_t::signal (int signal_)
+{
+    zs_assert (signal_ >= 0 && signal_ < wait_signal);
+    if (bits.btsr (signal_, wait_signal))
+        sem.post (); 
+}
+
+zs::ypollset_t::signals_t zs::ypollset_t::poll ()
+{
+    signals_t result = 0;
+    while (!result) {
+        result = bits.izte (signals_t (1) << wait_signal, 0);
+        if (!result) {
+            sem.wait ();
+            result = bits.xchg (0);
+        }
+
+        //  If btsr was really atomic, result would never be 0 at this
+        //  point, i.e. no looping would be possible. However, to
+        //  support even CPU architectures without CAS instruction
+        //  we allow btsr to be composed of two independent atomic
+        //  operation (set and reset). In such case looping can occur
+        //  sporadically.
+    }
+    return result;      
+}
+
+zs::ypollset_t::signals_t zs::ypollset_t::check ()
+{
+    return bits.xchg (0);
+}
diff --git a/src/ypollset.hpp b/src/ypollset.hpp
new file mode 100644
index 0000000..7c71152
--- /dev/null
+++ b/src/ypollset.hpp
@@ -0,0 +1,74 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_YPOLLSET_HPP_INCLUDED__
+#define __ZS_YPOLLSET_HPP_INCLUDED__
+
+#include "i_signaler.hpp"
+#include "simple_semaphore.hpp"
+#include "atomic_bitmap.hpp"
+
+namespace zs
+{
+
+    //  ypollset allows for rapid polling for up to constant number of  
+    //  different signals each produced by a different thread. The number of
+    //  possible signals is platform-dependent.
+
+    class ypollset_t : public i_signaler
+    {
+    public:
+
+        typedef atomic_bitmap_t::bitmap_t signals_t;
+
+        //  Create the pollset.
+        ypollset_t ();
+
+        //  Send a signal to the pollset (i_singnaler implementation).
+        void signal (int signal_);
+
+        //  Wait for signal. Returns a set of signals in form of a bitmap.
+        //  Signal with index 0 corresponds to value 1, index 1 to value 2,
+        //  index 2 to value 3 etc.
+        signals_t poll ();
+
+        //  Same as poll, however, if there is no signal available,
+        //  function returns zero immediately instead of waiting for a signal.
+        signals_t check ();
+
+    private:
+
+        //  Wait signal is carried in the most significant bit of integer.
+        enum {wait_signal = sizeof (signals_t) * 8 - 1};
+
+        //  The bits of the pollset.
+        atomic_bitmap_t bits;
+
+        //  Used by thread waiting for signals to sleep if there are no
+        //  signals available.
+        simple_semaphore_t sem;
+
+        //  Disable copying of ypollset object.
+        ypollset_t (const ypollset_t&);
+        void operator = (const ypollset_t&);
+    };
+
+}
+
+#endif
diff --git a/src/yqueue.hpp b/src/yqueue.hpp
new file mode 100644
index 0000000..78be17c
--- /dev/null
+++ b/src/yqueue.hpp
@@ -0,0 +1,138 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_YQUEUE_HPP_INCLUDED__
+#define __ZS_YQUEUE_HPP_INCLUDED__
+
+#include <stddef.h>
+
+#include "err.hpp"
+
+namespace zs
+{
+
+    //  yqueue is an efficient queue implementation. The main goal is
+    //  to minimise number of allocations/deallocations needed. Thus yqueue
+    //  allocates/deallocates elements in batches of N.
+    //
+    //  yqueue allows one thread to use push/back function and another one 
+    //  to use pop/front functions. However, user must ensure that there's no
+    //  pop on the empty queue and that both threads don't access the same
+    //  element in unsynchronised manner.
+    //
+    //  T is the type of the object in the queue
+    //  N is granularity of the queue (how many pushes have to be done till
+    //  actual memory allocation is required)
+
+    template <typename T, int N> class yqueue_t
+    {
+    public:
+
+        //  Create the queue.
+        inline yqueue_t ()
+        {
+             begin_chunk = new chunk_t;
+             zs_assert (begin_chunk);
+             begin_pos = 0;
+             back_chunk = NULL;
+             back_pos = 0;
+             end_chunk = begin_chunk;
+             end_pos = 0;
+        }
+
+        //  Destroy the queue.
+        inline ~yqueue_t ()
+        {
+            while (true) {
+                chunk_t *o = begin_chunk;
+                begin_chunk = begin_chunk->next;
+                delete o;
+                if (o == end_chunk)
+                    break;
+            }
+        }
+
+        //  Returns reference to the front element of the queue.
+        //  If the queue is empty, behaviour is undefined.
+        inline T &front ()
+        {
+             return begin_chunk->values [begin_pos];
+        }
+
+        //  Returns reference to the back element of the queue.
+        //  If the queue is empty, behaviour is undefined.
+        inline T &back ()
+        {
+            return back_chunk->values [back_pos];
+        }
+
+        //  Adds an element to the back end of the queue.
+        inline void push ()
+        {
+            back_chunk = end_chunk;
+            back_pos = end_pos;
+
+            if (++ end_pos != N)
+                return;
+
+            end_chunk->next = new chunk_t;
+            zs_assert (end_chunk->next);
+            end_chunk = end_chunk->next;
+            end_pos = 0;
+        }
+
+        //  Removes an element from the front end of the queue.
+        inline void pop ()
+        {
+            if (++ begin_pos == N) {
+                chunk_t *o = begin_chunk;
+                begin_chunk = begin_chunk->next;
+                begin_pos = 0;
+                delete o;
+            }
+        }
+
+    private:
+
+        //  Individual memory chunk to hold N elements.
+        struct chunk_t
+        {
+             T values [N];
+             chunk_t *next;
+        };
+
+        //  Back position may point to invalid memory if the queue is empty,
+        //  while begin & end positions are always valid. Begin position is
+        //  accessed exclusively be queue reader (front/pop), while back and
+        //  end positions are accessed exclusively by queue writer (back/push).
+        chunk_t *begin_chunk;
+        int begin_pos;
+        chunk_t *back_chunk;
+        int back_pos;
+        chunk_t *end_chunk;
+        int end_pos;
+
+        //  Disable copying of yqueue.
+        yqueue_t (const yqueue_t&);
+        void operator = (const yqueue_t&);
+    };
+
+}
+
+#endif
diff --git a/src/zmq_decoder.cpp b/src/zmq_decoder.cpp
new file mode 100644
index 0000000..46e4752
--- /dev/null
+++ b/src/zmq_decoder.cpp
@@ -0,0 +1,78 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "zmq_decoder.hpp"
+#include "i_session.hpp"
+#include "wire.hpp"
+
+zs::zmq_decoder_t::zmq_decoder_t () :
+    destination (NULL)
+{
+    zs_msg_init (&in_progress);
+
+    //  At the beginning, read one byte and go to one_byte_size_ready state.
+    next_step (tmpbuf, 1, &zmq_decoder_t::one_byte_size_ready);
+}
+
+zs::zmq_decoder_t::~zmq_decoder_t ()
+{
+    zs_msg_close (&in_progress);
+}
+
+void zs::zmq_decoder_t::set_session (i_session *destination_)
+{
+    destination = destination_;
+}
+
+bool zs::zmq_decoder_t::one_byte_size_ready ()
+{
+    //  First byte of size is read. If it is 0xff read 8-byte size.
+    //  Otherwise allocate the buffer for message data and read the
+    //  message data into it.
+    if (*tmpbuf == 0xff)
+        next_step (tmpbuf, 8, &zmq_decoder_t::eight_byte_size_ready);
+    else {
+        zs_msg_init_size (&in_progress, *tmpbuf);
+        next_step (zs_msg_data (&in_progress), *tmpbuf,
+            &zmq_decoder_t::message_ready);
+    }
+    return true;
+}
+
+bool zs::zmq_decoder_t::eight_byte_size_ready ()
+{
+    //  8-byte size is read. Allocate the buffer for message body and
+    //  read the message data into it.
+    size_t size = (size_t) get_uint64 (tmpbuf);
+    zs_msg_init_size (&in_progress, size);
+    next_step (zs_msg_data (&in_progress), size, &zmq_decoder_t::message_ready);
+    return true;
+}
+
+bool zs::zmq_decoder_t::message_ready ()
+{
+    //  Message is completely read. Push it further and start reading
+    //  new message.
+    if (!destination->write (&in_progress))
+        return false;
+
+    next_step (tmpbuf, 1, &zmq_decoder_t::one_byte_size_ready);
+    return true;
+}
+
diff --git a/src/zmq_decoder.hpp b/src/zmq_decoder.hpp
new file mode 100644
index 0000000..3ab8d6b
--- /dev/null
+++ b/src/zmq_decoder.hpp
@@ -0,0 +1,57 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef __ZS_ZMQ_DECODER_HPP_INCLUDED__
+#define __ZS_ZMQ_DECODER_HPP_INCLUDED__
+
+#include "../include/zs.h"
+
+#include "decoder.hpp"
+
+namespace zs
+{
+    //  Decoder for 0MQ backend protocol. Converts data batches into messages.
+
+    class zmq_decoder_t : public decoder_t <zmq_decoder_t>
+    {
+    public:
+
+        zmq_decoder_t ();
+        ~zmq_decoder_t ();
+
+        void set_session (struct i_session *destination_);
+
+    private:
+
+        bool one_byte_size_ready ();
+        bool eight_byte_size_ready ();
+        bool message_ready ();
+
+        struct i_session *destination;
+        unsigned char tmpbuf [8];
+        ::zs_msg in_progress;
+
+        zmq_decoder_t (const zmq_decoder_t&);
+        void operator = (const zmq_decoder_t&);
+    };
+
+}
+
+#endif
diff --git a/src/zmq_encoder.cpp b/src/zmq_encoder.cpp
new file mode 100644
index 0000000..9624b69
--- /dev/null
+++ b/src/zmq_encoder.cpp
@@ -0,0 +1,75 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "zmq_encoder.hpp"
+#include "i_session.hpp"
+#include "wire.hpp"
+
+zs::zmq_encoder_t::zmq_encoder_t () :
+    source (NULL)
+{
+    zs_msg_init (&in_progress);
+
+    //  Write 0 bytes to the batch and go to message_ready state.
+    next_step (NULL, 0, &zmq_encoder_t::message_ready, true);
+}
+
+zs::zmq_encoder_t::~zmq_encoder_t ()
+{
+    zs_msg_close (&in_progress);
+}
+
+void zs::zmq_encoder_t::set_session (i_session *source_)
+{
+    source = source_;
+}
+
+bool zs::zmq_encoder_t::size_ready ()
+{
+    //  Write message body into the buffer.
+    next_step (zs_msg_data (&in_progress), zs_msg_size (&in_progress),
+        &zmq_encoder_t::message_ready, false);
+    return true;
+}
+
+bool zs::zmq_encoder_t::message_ready ()
+{
+    //  Read new message from the dispatcher. If there is none, return false.
+    //  Note that new state is set only if write is successful. That way
+    //  unsuccessful write will cause retry on the next state machine
+    //  invocation.
+    if (!source->read (&in_progress)) {
+        return false;
+    }
+    size_t size = zs_msg_size (&in_progress);
+
+    //  For messages less than 255 bytes long, write one byte of message size.
+    //  For longer messages write 0xff escape character followed by 8-byte
+    //  message size.
+    if (size < 255) {
+        tmpbuf [0] = (unsigned char) size;
+        next_step (tmpbuf, 1, &zmq_encoder_t::size_ready, true);
+    }
+    else {
+        tmpbuf [0] = 0xff;
+        put_uint64 (tmpbuf + 1, size);
+        next_step (tmpbuf, 9, &zmq_encoder_t::size_ready, true);
+    }
+    return true;
+}
diff --git a/src/zmq_encoder.hpp b/src/zmq_encoder.hpp
new file mode 100644
index 0000000..37c4aee
--- /dev/null
+++ b/src/zmq_encoder.hpp
@@ -0,0 +1,54 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ZMQ_ENCODER_HPP_INCLUDED__
+#define __ZS_ZMQ_ENCODER_HPP_INCLUDED__
+
+#include "../include/zs.h"
+
+#include "encoder.hpp"
+
+namespace zs
+{
+    //  Encoder for 0MQ backend protocol. Converts messages into data batches.
+
+    class zmq_encoder_t : public encoder_t <zmq_encoder_t>
+    {
+    public:
+
+        zmq_encoder_t ();
+        ~zmq_encoder_t ();
+
+        void set_session (struct i_session *source_);
+
+    private:
+
+        bool size_ready ();
+        bool message_ready ();
+
+        struct i_session *source;
+        ::zs_msg in_progress;
+        unsigned char tmpbuf [9];
+
+        zmq_encoder_t (const zmq_encoder_t&);
+        void operator = (const zmq_encoder_t&);
+    };
+}
+
+#endif
diff --git a/src/zmq_tcp_engine.cpp b/src/zmq_tcp_engine.cpp
new file mode 100644
index 0000000..0f55808
--- /dev/null
+++ b/src/zmq_tcp_engine.cpp
@@ -0,0 +1,185 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "zmq_tcp_engine.hpp"
+#include "config.hpp"
+#include "i_session.hpp"
+#include "err.hpp"
+
+zs::zmq_tcp_engine_t::zmq_tcp_engine_t (fd_t fd_) :
+    poller (NULL),
+    session (NULL),
+    terminating (false),
+    insize (0),
+    inpos (0),
+    outsize (0),
+    outpos (0)
+{
+    //  Allocate read & write buffer.
+    inbuf = new unsigned char [in_batch_size];
+    zs_assert (inbuf);
+    outbuf = new unsigned char [out_batch_size];
+    zs_assert (outbuf);
+
+    //  Attach the socket.
+    int rc = socket.open (fd_);
+    zs_assert (rc == 0);
+}
+
+void zs::zmq_tcp_engine_t::attach (i_poller *poller_, i_session *session_)
+{
+    zs_assert (!poller);
+    poller = poller_;
+    zs_assert (!session);
+    session = session_;
+    encoder.set_session (session);
+    decoder.set_session (session);
+
+    //  Let session know we are here.
+    session->set_engine (this);
+
+    //  Register the engine with the polling thread.
+    handle = poller->add_fd (socket.get_fd (), this);
+    poller->set_pollin (handle);
+    poller->set_pollout (handle);
+
+    //  Flush any pending inbound messages.
+    in_event ();
+}
+
+void zs::zmq_tcp_engine_t::detach ()
+{
+    zs_assert (poller);
+    poller->rm_fd (handle);
+    poller = NULL;
+    zs_assert (session);
+    session->set_engine (NULL);
+    session = NULL;
+    encoder.set_session (NULL);
+    decoder.set_session (NULL);
+}
+
+void zs::zmq_tcp_engine_t::revive ()
+{
+    zs_assert (poller);
+    poller->set_pollout (handle);
+}
+
+void zs::zmq_tcp_engine_t::schedule_terminate ()
+{
+    terminating = true;
+}
+
+void zs::zmq_tcp_engine_t::terminate ()
+{
+    delete this;
+}
+
+void zs::zmq_tcp_engine_t::shutdown ()
+{
+    delete this;
+}
+
+zs::zmq_tcp_engine_t::~zmq_tcp_engine_t ()
+{
+    detach ();
+    delete [] outbuf;
+    delete [] inbuf;
+}
+
+void zs::zmq_tcp_engine_t::in_event ()
+{
+    //  If there's no data to process in the buffer, read new data.
+    if (inpos == insize) {
+
+        //  Read as much data as possible to the read buffer.
+        insize = socket.read (inbuf, in_batch_size);
+        inpos = 0;
+
+        //  Check whether the peer has closed the connection.
+        if (insize == -1) {
+            insize = 0;
+            error ();
+            return;
+        }
+    }
+
+    //  Following code should be executed even if there's not a single byte in
+    //  the buffer. There still can be a decoded messages stored in the decoder.
+
+    //  Push the data to the decoder.
+    int nbytes = decoder.write (inbuf + inpos, insize - inpos);
+
+    //  Adjust read position. Stop polling for input if we got stuck.
+    inpos += nbytes;
+    if (inpos < insize)
+        poller->reset_pollin (handle);
+
+    //  If at least one byte was processed, flush all messages the decoder
+    //  may have produced. If engine is disconnected from session, no need
+    //  to flush the messages. It's important that flush is called at the
+    //  very end of in_event as it may invoke in_event itself.
+    if (nbytes > 0 && session)
+        session->flush ();
+}
+
+void zs::zmq_tcp_engine_t::out_event ()
+{
+    //  If write buffer is empty, try to read new data from the encoder.
+    if (outpos == outsize) {
+
+        outsize = encoder.read (outbuf, out_batch_size);
+        outpos = 0;
+
+        //  If there are no more pipes, engine can be deallocated.
+        if (terminating) {
+            terminate ();
+            return;
+        }
+
+        //  If there is no data to send, stop polling for output.
+        if (outsize == 0)
+            poller->reset_pollout (handle);
+    }
+
+    //  If there are any data to write in write buffer, write as much as
+    //  possible to the socket.
+    if (outpos < outsize) {
+        int nbytes = socket.write (outbuf + outpos, outsize - outpos);
+
+        //  Handle problems with the connection.
+        if (nbytes == -1) {
+            error ();
+            return;
+        }
+
+        outpos += nbytes;
+    }
+}
+
+void zs::zmq_tcp_engine_t::timer_event ()
+{
+    zs_assert (false);
+}
+
+void zs::zmq_tcp_engine_t::error ()
+{
+    zs_assert (false);
+}
+
diff --git a/src/zmq_tcp_engine.hpp b/src/zmq_tcp_engine.hpp
new file mode 100644
index 0000000..fb1413c
--- /dev/null
+++ b/src/zmq_tcp_engine.hpp
@@ -0,0 +1,92 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZS_ZMQ_TCP_ENGINE_HPP_INCLUDED__
+#define __ZS_ZMQ_TCP_ENGINE_HPP_INCLUDED__
+
+#include "i_engine.hpp"
+#include "i_poller.hpp"
+#include "i_poll_events.hpp"
+#include "fd.hpp"
+#include "tcp_socket.hpp"
+#include "zmq_encoder.hpp"
+#include "zmq_decoder.hpp"
+
+namespace zs
+{
+
+    class zmq_tcp_engine_t : public i_engine, public i_poll_events
+    {
+    public:
+
+        zmq_tcp_engine_t (fd_t fd_);
+
+        //  i_engine implementation.
+        void attach (struct i_poller *poller_, struct i_session *session_);
+        void detach ();
+        void revive ();
+        void schedule_terminate ();
+        void terminate ();
+        void shutdown ();
+
+        //  i_poll_events implementation.
+        void in_event ();
+        void out_event ();
+        void timer_event ();
+
+    private:
+
+        void error ();
+
+        //  Clean-up.
+        ~zmq_tcp_engine_t ();
+
+        //  The underlying TCP socket.
+        tcp_socket_t socket;
+
+        //  Handle associated with the socket.
+        handle_t handle;
+
+        //  I/O thread that the engine runs in.
+        i_poller *poller;
+
+        //  Reference to the associated session object.
+        i_session *session;
+
+        //  If true, engine should terminate itself as soon as possible.
+        bool terminating;
+
+        unsigned char *inbuf;
+        int insize;
+        int inpos;
+
+        unsigned char *outbuf;
+        int outsize;
+        int outpos;
+
+        zmq_encoder_t encoder;
+        zmq_decoder_t decoder;
+
+        zmq_tcp_engine_t (const zmq_tcp_engine_t&);
+        void operator = (const zmq_tcp_engine_t&);
+    };
+
+}
+
+#endif
diff --git a/src/zs.cpp b/src/zs.cpp
new file mode 100644
index 0000000..ca05db3
--- /dev/null
+++ b/src/zs.cpp
@@ -0,0 +1,222 @@
+/*
+    Copyright (c) 2007-2009 FastMQ Inc.
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "../include/zs.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <new>
+
+#include "i_api.hpp"
+#include "err.hpp"
+#include "dispatcher.hpp"
+#include "msg.hpp"
+
+int zs_msg_init (zs_msg *msg_)
+{
+    msg_->content = (zs_msg_content*) ZS_VSM;
+    msg_->vsm_size = 0;
+    return 0;
+}
+
+int zs_msg_init_size (zs_msg *msg_, size_t size_)
+{
+    if (size_ <= ZS_MAX_VSM_SIZE) {
+        msg_->content = (zs_msg_content*) ZS_VSM;
+        msg_->vsm_size = (uint16_t) size_;
+    }
+    else {
+        msg_->content = (zs_msg_content*) malloc (sizeof (zs_msg_content) +
+            size_);
+        if (!msg_->content) {
+            errno = ENOMEM;
+            return -1;
+        }
+        msg_->shared = 0;
+            
+        msg_->content->data = (void*) (msg_->content + 1);
+        msg_->content->size = size_;
+        msg_->content->ffn = NULL;
+        new (&msg_->content->refcnt) zs::atomic_counter_t ();
+    }
+    return 0;
+}
+
+int zs_msg_init_data (zs_msg *msg_, void *data_, size_t size_, zs_free_fn *ffn_)
+{
+    msg_->shared = 0;
+    msg_->content = (zs_msg_content*) malloc (sizeof (zs_msg_content));
+    zs_assert (msg_->content);
+    msg_->content->data = data_;
+    msg_->content->size = size_;
+    msg_->content->ffn = ffn_;
+    new (&msg_->content->refcnt) zs::atomic_counter_t ();
+    return 0;
+}
+
+int zs_msg_close (zs_msg *msg_)
+{
+    //  For VSMs and delimiters there are no resources to free
+    if (msg_->content == (zs_msg_content*) ZS_DELIMITER ||
+          msg_->content == (zs_msg_content*) ZS_VSM ||
+          msg_->content == (zs_msg_content*) ZS_GAP)
+        return 0;
+
+    //  If the content is not shared, or if it is shared and the reference
+    //  count has dropped to zero, deallocate it.
+    if (!msg_->shared || !msg_->content->refcnt.sub (1)) {
+
+        //  We used "placement new" operator to initialize the reference
+        //  counter so we call its destructor now.
+        msg_->content->refcnt.~atomic_counter_t ();
+
+        if (msg_->content->ffn)
+            msg_->content->ffn (msg_->content->data);
+        free (msg_->content);
+    }
+
+    return 0;
+}
+
+int zs_msg_move (zs_msg *dest_, zs_msg *src_)
+{
+    zs_msg_close (dest_);
+    *dest_ = *src_;
+    zs_msg_init (src_);
+    return 0;
+}
+
+int zs_msg_copy (zs_msg *dest_, zs_msg *src_)
+{
+    zs_msg_close (dest_);
+
+    //  VSMs and delimiters require no special handling.
+    if (src_->content !=
+          (zs_msg_content*) ZS_DELIMITER &&
+          src_->content != (zs_msg_content*) ZS_VSM &&
+          src_->content != (zs_msg_content*) ZS_GAP) {
+
+        //  One reference is added to shared messages. Non-shared messages
+        //  are turned into shared messages and reference count is set to 2.
+        if (src_->shared)
+            src_->content->refcnt.add (1);
+        else {
+            src_->shared = true;
+            src_->content->refcnt.set (2);
+        }
+    }
+
+    *dest_ = *src_;
+    return 0;
+}
+
+void *zs_msg_data (zs_msg *msg_)
+{
+    if (msg_->content == (zs_msg_content*) ZS_VSM)
+        return msg_->vsm_data;
+    if (msg_->content ==
+          (zs_msg_content*) ZS_DELIMITER ||
+          msg_->content == (zs_msg_content*) ZS_GAP)
+        return NULL;
+    return msg_->content->data;
+}
+
+size_t zs_msg_size (zs_msg *msg_)
+{
+    if (msg_->content == (zs_msg_content*) ZS_VSM)
+        return msg_->vsm_size;
+    if (msg_->content ==
+          (zs_msg_content*) ZS_DELIMITER ||
+          msg_->content == (zs_msg_content*) ZS_GAP)
+        return 0;
+    return msg_->content->size;
+}
+
+int zs_msg_type (zs_msg *msg_)
+{
+    //  If it's a genuine message, return 0.
+    if (msg_->content >= (zs_msg_content*) ZS_VSM)
+            return 0;
+
+    //   Trick the compiler to believe that content is an integer.
+    unsigned char *offset = 0;
+    return (((const unsigned char*) msg_->content) - offset);
+}
+
+void *zs_init (int app_threads_, int io_threads_)
+{
+    //  There should be at least a single thread managed by the dispatcher.
+    if (app_threads_ < 0 || io_threads_ < 0 ||
+          app_threads_ + io_threads_ == 0) {
+        errno = EINVAL;
+        return NULL;
+    }
+
+    zs::dispatcher_t *dispatcher =
+        new zs::dispatcher_t (app_threads_, io_threads_);
+    zs_assert (dispatcher);
+    return (void*) dispatcher;
+}
+
+int zs_term (void *context_)
+{
+    ((zs::dispatcher_t*) context_)->shutdown ();
+    return 0;
+}
+
+void *zs_socket (void *context_, int type_)
+{
+    return (void*) (((zs::dispatcher_t*) context_)->create_socket (type_));
+}
+
+int zs_close (void *s_)
+{
+    ((zs::i_api*) s_)->close ();
+    return 0;
+}
+
+int zs_bind (void *s_, const char *addr_, zs_opts *opts_)
+{
+    return (((zs::i_api*) s_)->bind (addr_, opts_));
+}
+
+int zs_connect (void *s_, const char *addr_, zs_opts *opts_)
+{
+    return (((zs::i_api*) s_)->connect (addr_, opts_));
+}
+
+int zs_subscribe (void *s_, const char *criteria_)
+{
+    return (((zs::i_api*) s_)->subscribe (criteria_));
+}
+
+int zs_send (void *s_, zs_msg *msg_, int flags_)
+{
+    return (((zs::i_api*) s_)->send (msg_, flags_));
+}
+
+int zs_flush (void *s_)
+{
+    return (((zs::i_api*) s_)->flush ());
+}
+
+int zs_recv (void *s_, zs_msg *msg_, int flags_)
+{
+    return (((zs::i_api*) s_)->recv (msg_, flags_));
+}