pipes added

20 files changed, 679 insertions, 49 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 396e3a3..b6a4540 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -19,6 +19,7 @@ libzmq_la_SOURCES = \
     io_object.hpp \
     io_thread.hpp \
     ip.hpp \
+    i_endpoint.hpp \
     i_poller.hpp \
     i_poll_events.hpp \
     i_signaler.hpp \
@@ -66,6 +67,7 @@ libzmq_la_SOURCES = \
     object.cpp \
     options.cpp \
     owned.cpp \
+    pipe.cpp \
     poll.cpp \
     select.cpp \
     session.cpp \
diff --git a/src/app_thread.cpp b/src/app_thread.cpp
index 74ba357..db73ec1 100644
--- a/src/app_thread.cpp
+++ b/src/app_thread.cpp
@@ -77,7 +77,7 @@ bool zmq::app_thread_t::make_current ()
     return true;
 }
 
-void zmq::app_thread_t::process_commands (bool block_)
+void zmq::app_thread_t::process_commands (bool block_, bool throttle_)
 {
     ypollset_t::signals_t signals;
     if (block_)
@@ -91,24 +91,26 @@ void zmq::app_thread_t::process_commands (bool block_)
         //  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).
+        if (throttle_) {
 
-        //  Get timestamp counter.
+            //  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;
+            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 ();
+            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;
+            //  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.
diff --git a/src/app_thread.hpp b/src/app_thread.hpp
index e7bbf70..e45b1b2 100644
--- a/src/app_thread.hpp
+++ b/src/app_thread.hpp
@@ -53,7 +53,9 @@ namespace zmq
 
         //  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_);
+        //  If throttle argument is true, commands are processed at most once
+        //  in a predefined time period.
+        void process_commands (bool block_, bool throttle_);
 
         //  Create a socket of a specified type.
         class socket_base_t *create_socket (int type_);
diff --git a/src/command.hpp b/src/command.hpp
index 41c7d6c..d3bad79 100644
--- a/src/command.hpp
+++ b/src/command.hpp
@@ -39,6 +39,7 @@ namespace zmq
             own,
             attach,
             bind,
+            revive,
             term_req,
             term,
             term_ack
@@ -65,10 +66,18 @@ namespace zmq
                 class zmq_engine_t *engine;
             } attach;
 
-            //  Sent between objects to establish pipe(s) between them.
+            //  Sent from session to socket to establish pipe(s) between them.
             struct {
+                class owned_t *session;
+                class reader_t *in_pipe;
+                class writer_t *out_pipe;
             } bind;
 
+            //  Sent by pipe writer to inform dormant pipe reader that there
+            //  are messages in the pipe.
+            struct {
+            } revive;
+
             //  Sent by I/O object ot the socket to request the shutdown of
             //  the I/O object.
             struct {
diff --git a/src/config.hpp b/src/config.hpp
index 88b93d7..17e67b9 100644
--- a/src/config.hpp
+++ b/src/config.hpp
@@ -38,6 +38,14 @@ namespace zmq
         //  footprint of dispatcher.
         command_pipe_granularity = 4,
 
+        //  Determines how often does socket poll for new commands when it
+        //  still has unprocessed messages to handle. Thus, if it is set to 100,
+        //  socket will process 100 inbound messages before doing the poll.
+        //  If there are no unprocessed messages available, poll is done
+        //  immediately. Decreasing the value trades overall latency for more
+        //  real-time behaviour (less latency peaks).
+        inbound_poll_rate = 100,
+
         //  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
diff --git a/src/i_endpoint.hpp b/src/i_endpoint.hpp
new file mode 100644
index 0000000..bb7409e
--- /dev/null
+++ b/src/i_endpoint.hpp
@@ -0,0 +1,33 @@
+/*
+    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 __ZMQ_I_ENDPOINT_HPP_INCLUDED__
+#define __ZMQ_I_ENDPOINT_HPP_INCLUDED__
+
+namespace zmq
+{
+
+    struct i_endpoint
+    {
+        virtual void revive (class reader_t *pipe_) = 0;
+    };
+
+}
+
+#endif
diff --git a/src/object.cpp b/src/object.cpp
index 0a25750..4d54ebf 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -20,6 +20,7 @@
 #include "object.hpp"
 #include "dispatcher.hpp"
 #include "err.hpp"
+#include "pipe.hpp"
 #include "io_thread.hpp"
 #include "simple_semaphore.hpp"
 #include "owned.hpp"
@@ -57,6 +58,10 @@ void zmq::object_t::process_command (command_t &cmd_)
 {
     switch (cmd_.type) {
 
+    case command_t::revive:
+        process_revive ();
+        break;
+
     case command_t::stop:
         process_stop ();
         break;
@@ -74,7 +79,8 @@ void zmq::object_t::process_command (command_t &cmd_)
         return;
 
     case command_t::bind:
-        process_bind ();
+        process_bind (cmd_.args.bind.session,
+            cmd_.args.bind.in_pipe, cmd_.args.bind.out_pipe);
         return;
 
     case command_t::term_req:
@@ -140,11 +146,23 @@ void zmq::object_t::send_attach (session_t *destination_, zmq_engine_t *engine_)
     send_command (cmd);
 }
 
-void zmq::object_t::send_bind (object_t *destination_)
+void zmq::object_t::send_bind (object_t *destination_, owned_t *session_,
+    reader_t *in_pipe_, writer_t *out_pipe_)
 {
     command_t cmd;
     cmd.destination = destination_;
     cmd.type = command_t::bind;
+    cmd.args.bind.session = session_;
+    cmd.args.bind.in_pipe = in_pipe_;
+    cmd.args.bind.out_pipe = out_pipe_;
+    send_command (cmd);
+}
+
+void zmq::object_t::send_revive (object_t *destination_)
+{
+    command_t cmd;
+    cmd.destination = destination_;
+    cmd.type = command_t::revive;
     send_command (cmd);
 }
 
@@ -194,7 +212,13 @@ void zmq::object_t::process_attach (zmq_engine_t *engine_)
     zmq_assert (false);
 }
 
-void zmq::object_t::process_bind ()
+void zmq::object_t::process_bind (owned_t *session_,
+    reader_t *in_pipe_, writer_t *out_pipe_)
+{
+    zmq_assert (false);
+}
+
+void zmq::object_t::process_revive ()
 {
     zmq_assert (false);
 }
diff --git a/src/object.hpp b/src/object.hpp
index 31c8c40..0dbac24 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -24,7 +24,6 @@
 
 namespace zmq
 {
-
     //  Base class for all objects that participate in inter-thread
     //  communication.
 
@@ -58,7 +57,9 @@ namespace zmq
             class owned_t *object_);
         void send_attach (class session_t *destination_,
             class zmq_engine_t *engine_);
-        void send_bind (object_t *destination_);
+        void send_bind (object_t *destination_, class owned_t *session_,
+            class reader_t *in_pipe_, class writer_t *out_pipe_);
+        void send_revive (class object_t *destination_);
         void send_term_req (class socket_base_t *destination_,
             class owned_t *object_);
         void send_term (class owned_t *destination_);
@@ -70,7 +71,9 @@ namespace zmq
         virtual void process_plug ();
         virtual void process_own (class owned_t *object_);
         virtual void process_attach (class zmq_engine_t *engine_);
-        virtual void process_bind ();
+        virtual void process_bind (class owned_t *session_,
+            class reader_t *in_pipe_, class writer_t *out_pipe_);
+        virtual void process_revive ();
         virtual void process_term_req (class owned_t *object_);
         virtual void process_term ();
         virtual void process_term_ack ();
diff --git a/src/pipe.cpp b/src/pipe.cpp
new file mode 100644
index 0000000..5016631
--- /dev/null
+++ b/src/pipe.cpp
@@ -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/>.
+*/
+
+#include <pthread.h>
+
+#include "pipe.hpp"
+
+zmq::reader_t::reader_t (object_t *parent_, pipe_t *pipe_,
+      uint64_t hwm_, uint64_t lwm_) :
+    object_t (parent_),
+    pipe (pipe_),
+    peer (&pipe_->writer),
+    hwm (hwm_),
+    lwm (lwm_),
+    index (-1),
+    endpoint (NULL)
+{
+}
+
+zmq::reader_t::~reader_t ()
+{
+}
+
+bool zmq::reader_t::read (zmq_msg_t *msg_)
+{
+    return pipe->read (msg_);
+
+    //  TODO: Adjust the size of the pipe.
+}
+
+void zmq::reader_t::set_endpoint (i_endpoint *endpoint_)
+{
+    endpoint = endpoint_;
+}
+
+void zmq::reader_t::set_index (int index_)
+{
+    index = index_;
+}
+
+int zmq::reader_t::get_index ()
+{
+    return index;
+}
+
+void zmq::reader_t::process_revive ()
+{
+    endpoint->revive (this);
+}
+
+zmq::writer_t::writer_t (object_t *parent_, pipe_t *pipe_,
+      uint64_t hwm_, uint64_t lwm_) :
+    object_t (parent_),
+    pipe (pipe_),
+    peer (&pipe_->reader),
+    hwm (hwm_),
+    lwm (lwm_)
+{
+}
+
+zmq::writer_t::~writer_t ()
+{
+}
+
+bool zmq::writer_t::check_write (uint64_t size_)
+{
+    //  TODO: Check whether hwm is exceeded.
+
+    return true;
+}
+
+bool zmq::writer_t::write (struct zmq_msg_t *msg_)
+{
+    pipe->write (*msg_);
+    return true;
+
+    //  TODO: Adjust size of the pipe.
+}
+
+void zmq::writer_t::flush ()
+{
+    if (!pipe->flush ())
+        send_revive (peer);
+}
+
+zmq::pipe_t::pipe_t (object_t *reader_parent_, object_t *writer_parent_,
+      uint64_t hwm_, uint64_t lwm_) :
+    reader (reader_parent_, this, hwm_, lwm_),
+    writer (writer_parent_, this, hwm_, lwm_)
+{
+}
+
+zmq::pipe_t::~pipe_t ()
+{
+}
+
diff --git a/src/pipe.hpp b/src/pipe.hpp
index 28e4b4d..d48fc47 100644
--- a/src/pipe.hpp
+++ b/src/pipe.hpp
@@ -22,15 +22,117 @@
 
 #include "../include/zmq.h"
 
+#include "stdint.hpp"
+#include "i_endpoint.hpp"
 #include "ypipe.hpp"
 #include "config.hpp"
+#include "object.hpp"
 
 namespace zmq
 {
 
+    class reader_t : public object_t
+    {
+    public:
+
+        reader_t (class object_t *parent_, class pipe_t *pipe_,
+            uint64_t hwm_, uint64_t lwm_);
+        ~reader_t ();
+
+        //  Reads a message to the underlying pipe.
+        bool read (struct zmq_msg_t *msg_);
+
+        //  Mnaipulation of index of the pipe.
+        void set_endpoint (i_endpoint *endpoint_);
+        void set_index (int index_);
+        int get_index ();
+
+    private:
+
+        //  Command handlers.
+        void process_revive ();
+
+        //  The underlying pipe.
+        class pipe_t *pipe;
+
+        //  Pipe writer associated with the other side of the pipe.
+        class object_t *peer;
+
+        //  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;
+
+        //  Index of the pipe in the socket's list of inbound pipes.
+        int index;
+
+        //  Endpoint (either session or socket) the pipe is attached to.
+        i_endpoint *endpoint;
+
+        reader_t (const reader_t&);
+        void operator = (const reader_t&);
+    };
+
+    class writer_t : public object_t
+    {
+    public:
+
+        writer_t (class object_t *parent_, class pipe_t *pipe_,
+            uint64_t hwm_, uint64_t lwm_);
+        ~writer_t ();
+
+        //  Checks whether message with specified size can be written to the
+        //  pipe. If writing the message would cause high watermark to be
+        //  exceeded, the function returns false.
+        bool check_write (uint64_t size_);
+
+        //  Writes a message to the underlying pipe. Returns false if the
+        //  message cannot be written because high watermark was reached.
+        bool write (struct zmq_msg_t *msg_);
+
+        //  Flush the messages downsteam.
+        void flush ();
+
+    private:
+
+        //  The underlying pipe.
+        class pipe_t *pipe;
+
+        //  Pipe reader associated with the other side of the pipe.
+        class object_t *peer;
+
+        //  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;
+
+        writer_t (const writer_t&);
+        void operator = (const writer_t&);
+    };
+
     //  Message pipe.
     class pipe_t : public ypipe_t <zmq_msg_t, false, message_pipe_granularity>
     {
+    public:
+
+        pipe_t (object_t *reader_parent_, object_t *writer_parent_,
+            uint64_t hwm_, uint64_t lwm_);
+        ~pipe_t ();
+
+        reader_t reader;
+        writer_t writer;
+
+    private:
+
+        pipe_t (const pipe_t&);
+        void operator = (const pipe_t&);
     };
 
 }
diff --git a/src/session.cpp b/src/session.cpp
index fc1f858..115fb85 100644
--- a/src/session.cpp
+++ b/src/session.cpp
@@ -20,12 +20,17 @@
 #include "session.hpp"
 #include "zmq_engine.hpp"
 #include "err.hpp"
+#include "pipe.hpp"
 
 zmq::session_t::session_t (object_t *parent_, socket_base_t *owner_,
-      const char *name_) :
+      const char *name_, const options_t &options_) :
     owned_t (parent_, owner_),
+    in_pipe (NULL),
+    active (false),
+    out_pipe (NULL),
     engine (NULL),
-    name (name_)
+    name (name_),
+    options (options_)
 {
 }
 
@@ -33,18 +38,48 @@ zmq::session_t::~session_t ()
 {
 }
 
+void zmq::session_t::set_inbound_pipe (reader_t *pipe_)
+{
+    zmq_assert (!in_pipe);
+    in_pipe = pipe_;
+    active = true;
+    in_pipe->set_endpoint (this);
+}
+void zmq::session_t::set_outbound_pipe (writer_t *pipe_)
+{
+    zmq_assert (!out_pipe);
+    out_pipe = pipe_;
+}
+
+
 bool zmq::session_t::read (::zmq_msg_t *msg_)
 {
-    return false;
+    if (!active)
+        return false;
+
+    bool fetched = in_pipe->read (msg_);
+    if (!fetched)
+        active = false;
+
+    return fetched;
 }
 
 bool zmq::session_t::write (::zmq_msg_t *msg_)
 {
-    return false;
+    return out_pipe->write (msg_);
 }
 
 void zmq::session_t::flush ()
 {
+    out_pipe->flush ();
+}
+
+void zmq::session_t::revive (reader_t *pipe_)
+{
+    zmq_assert (in_pipe == pipe_);
+    active = true;
+    if (engine)
+        engine->revive ();
 }
 
 void zmq::session_t::process_plug ()
@@ -56,6 +91,19 @@ void zmq::session_t::process_plug ()
     //  We should syslog it and drop the session. TODO
     zmq_assert (ok);
 
+    //  If session is created by 'connect' function, it has the pipes set
+    //  already. Otherwise, it's being created by the listener and the pipes
+    //  are yet to be created.
+    if (!in_pipe && !out_pipe) {
+        pipe_t *inbound = new pipe_t (this, owner, options.hwm, options.lwm);
+        zmq_assert (inbound);
+        in_pipe = &inbound->reader;
+        pipe_t *outbound = new pipe_t (owner, this, options.hwm, options.lwm);
+        zmq_assert (outbound);
+        out_pipe = &outbound->writer;
+        send_bind (owner, this, &outbound->reader, &inbound->writer);
+    }
+
     owned_t::process_plug ();
 }
 
diff --git a/src/session.hpp b/src/session.hpp
index 6d6bcf7..b79fb4b 100644
--- a/src/session.hpp
+++ b/src/session.hpp
@@ -23,17 +23,22 @@
 #include <string>
 
 #include "i_inout.hpp"
+#include "i_endpoint.hpp"
 #include "owned.hpp"
 #include "options.hpp"
 
 namespace zmq
 {
 
-    class session_t : public owned_t, public i_inout
+    class session_t : public owned_t, public i_inout, public i_endpoint
     {
     public:
 
-        session_t (object_t *parent_, socket_base_t *owner_, const char *name_);
+        session_t (object_t *parent_, socket_base_t *owner_, const char *name_,
+            const options_t &options_);
+
+        void set_inbound_pipe (class reader_t *pipe_);
+        void set_outbound_pipe (class writer_t *pipe_);
 
     private:
 
@@ -44,17 +49,32 @@ namespace zmq
         bool write (::zmq_msg_t *msg_);
         void flush ();
 
+        //  i_endpoint interface implementation.
+        void revive (class reader_t *pipe_);
+
         //  Handlers for incoming commands.
         void process_plug ();
         void process_unplug ();
         void process_attach (class zmq_engine_t *engine_);
 
+        //  Inbound pipe, i.e. one the session is getting messages from.
+        class reader_t *in_pipe;
+
+        //  If true, in_pipe is active. Otherwise there are no messages to get.
+        bool active;
+
+        //  Outbound pipe, i.e. one the socket is sending messages to.
+        class writer_t *out_pipe;
+
         class zmq_engine_t *engine;
 
         //  The name of the session. One that is used to register it with
         //  socket-level repository of sessions.
         std::string name;
 
+        //  Inherited socket options.
+        options_t options;
+
         session_t (const session_t&);
         void operator = (const session_t&);
     };
diff --git a/src/socket_base.cpp b/src/socket_base.cpp
index fb7bdcf..68fc82b 100644
--- a/src/socket_base.cpp
+++ b/src/socket_base.cpp
@@ -27,18 +27,23 @@
 #include "err.hpp"
 #include "zmq_listener.hpp"
 #include "zmq_connecter.hpp"
+#include "msg_content.hpp"
 #include "io_thread.hpp"
 #include "session.hpp"
 #include "config.hpp"
 #include "owned.hpp"
 #include "uuid.hpp"
+#include "pipe.hpp"
 
 zmq::socket_base_t::socket_base_t (app_thread_t *parent_) :
     object_t (parent_),
+    current (0),
+    active (0),
     pending_term_acks (0),
+    ticks (0),
     app_thread (parent_),
     shutting_down (false)
-{    
+{
 }
 
 zmq::socket_base_t::~socket_base_t ()
@@ -65,7 +70,7 @@ zmq::socket_base_t::~socket_base_t ()
 
         //  Process commands till we get all the termination acknowledgements.
         while (pending_term_acks)
-            app_thread->process_commands (true);
+            app_thread->process_commands (true, false);
     }
 
     //  Check whether there are no session leaks.
@@ -150,8 +155,28 @@ int zmq::socket_base_t::connect (const char *addr_)
 
     //  Create the session.
     io_thread_t *io_thread = choose_io_thread (options.affinity);
-    session_t *session = new session_t (io_thread, this, session_name.c_str ());
+    session_t *session = new session_t (io_thread, this, session_name.c_str (),
+        options);
     zmq_assert (session);
+
+    //  Create inbound pipe.
+    pipe_t *in_pipe = new pipe_t (this, session, options.hwm, options.lwm);
+    zmq_assert (in_pipe);
+    in_pipe->reader.set_endpoint (this);
+    session->set_outbound_pipe (&in_pipe->writer);
+    in_pipes.push_back (std::make_pair (&in_pipe->reader, session));
+    in_pipes.back ().first->set_index (active);
+    in_pipes [active].first->set_index (in_pipes.size () - 1);
+    std::swap (in_pipes.back (), in_pipes [active]);
+    active++;
+
+    //  Create outbound pipe.
+    pipe_t *out_pipe = new pipe_t (session, this, options.hwm, options.lwm);
+    zmq_assert (out_pipe);
+    session->set_inbound_pipe (&out_pipe->reader);
+    out_pipes.push_back (std::make_pair (&out_pipe->writer, session));
+
+    //  Activate the session.
     send_plug (session);
     send_own (this, session);
 
@@ -173,17 +198,79 @@ int zmq::socket_base_t::connect (const char *addr_)
 
 int zmq::socket_base_t::send (::zmq_msg_t *msg_, int flags_)
 {
-    zmq_assert (false);
+    //  Process pending commands, if any.
+    app_thread->process_commands (false, true);
+
+    //  Try to send the message.
+    bool sent = distribute (msg_, !(flags_ & ZMQ_NOFLUSH));
+
+    if (!(flags_ & ZMQ_NOBLOCK)) {
+
+        //  Oops, we couldn't send the message. Wait for the next
+        //  command, process it and try to send the message again.
+        while (!sent) {
+            app_thread->process_commands (true, false);
+            sent = distribute (msg_, !(flags_ & ZMQ_NOFLUSH));
+        }
+    }
+    else if (!sent) {
+        errno = EAGAIN;
+        return -1;
+    }
+
+    return 0;
 }
 
 int zmq::socket_base_t::flush ()
 {
-    zmq_assert (false);
+    for (out_pipes_t::iterator it = out_pipes.begin (); it != out_pipes.end ();
+          it++)
+        it->first->flush ();
+
+    return 0;
 }
 
 int zmq::socket_base_t::recv (::zmq_msg_t *msg_, int flags_)
 {
-    zmq_assert (false);
+    //  If the message cannot be fetched immediately, there are two scenarios.
+    //  For non-blocking recv, commands are processed in case there's a message
+    //  already waiting we don't know about. If it's not, return EAGAIN.
+    //  In blocking scenario, commands are processed over and over again until
+    //  we are able to fetch a message.
+    bool fetched = fetch (msg_);
+    if (!fetched) {
+        if (flags_ & ZMQ_NOBLOCK) {
+            app_thread->process_commands (false, false);
+            fetched = fetch (msg_);
+        }
+        else  {
+            while (!fetched) {
+                app_thread->process_commands (true, false);
+                ticks = 0;
+                fetched = fetch (msg_);
+            }
+        }
+    }
+
+    //  Once every inbound_poll_rate messages check for signals and process
+    //  incoming commands. This happens only if we are not polling altogether
+    //  because there are messages available all the time. If poll occurs,
+    //  ticks is set to zero and thus we avoid this code.
+    //
+    //  Note that 'recv' uses different command throttling algorithm (the one
+    //  described above) from the one used by 'send'. This is because counting
+    //  ticks is more efficient than doing rdtsc all the time.
+    if (++ticks == inbound_poll_rate) {
+        app_thread->process_commands (false, false);
+        ticks = 0;
+    }
+
+    if (!fetched) {
+        errno = EAGAIN;
+        return -1;
+    }
+
+    return 0;
 }
 
 int zmq::socket_base_t::close ()
@@ -229,11 +316,35 @@ zmq::session_t *zmq::socket_base_t::find_session (const char *name_)
     return it->second;    
 }
 
+void zmq::socket_base_t::revive (reader_t *pipe_)
+{
+    //  Move the pipe to the list of active pipes.
+    in_pipes_t::size_type index = (in_pipes_t::size_type) pipe_->get_index ();
+    in_pipes [index].first->set_index (active);
+    in_pipes [active].first->set_index (index);    
+    std::swap (in_pipes [index], in_pipes [active]);
+    active++;
+}
+
 void zmq::socket_base_t::process_own (owned_t *object_)
 {
     io_objects.insert (object_);
 }
 
+void zmq::socket_base_t::process_bind (owned_t *session_,
+    reader_t *in_pipe_, writer_t *out_pipe_)
+{
+    zmq_assert (in_pipe_);
+    in_pipe_->set_endpoint (this);
+    in_pipes.push_back (std::make_pair (in_pipe_, session_));
+    in_pipes.back ().first->set_index (active);
+    in_pipes [active].first->set_index (in_pipes.size () - 1);
+    std::swap (in_pipes.back (), in_pipes [active]);
+    active++;
+    zmq_assert (out_pipe_);
+    out_pipes.push_back (std::make_pair (out_pipe_, session_));
+}
+
 void zmq::socket_base_t::process_term_req (owned_t *object_)
 {
     //  When shutting down we can ignore termination requests from owned
@@ -260,3 +371,107 @@ void zmq::socket_base_t::process_term_ack ()
     zmq_assert (pending_term_acks);
     pending_term_acks--;
 }
+
+bool zmq::socket_base_t::distribute (zmq_msg_t *msg_, bool flush_)
+{
+    int pipes_count = out_pipes.size ();
+
+    //  If there are no pipes available, simply drop the message.
+    if (pipes_count == 0) {
+        int rc = zmq_msg_close (msg_);
+        zmq_assert (rc == 0);
+        rc = zmq_msg_init (msg_);
+        zmq_assert (rc == 0);
+        return true;
+    }
+
+    //  First check whether all pipes are available for writing.
+    for (out_pipes_t::iterator it = out_pipes.begin (); it != out_pipes.end ();
+          it++)
+        if (!it->first->check_write (zmq_msg_size (msg_)))
+            return false;
+
+    msg_content_t *content = (msg_content_t*) msg_->content;
+
+    //  For VSMs the copying is straighforward.
+    if (content == (msg_content_t*) ZMQ_VSM) {
+        for (out_pipes_t::iterator it = out_pipes.begin ();
+              it != out_pipes.end (); it++) {
+            it->first->write (msg_);
+            if (flush_)
+                it->first->flush ();
+        }
+        int rc = zmq_msg_init (msg_);
+        zmq_assert (rc == 0);
+        return true;
+    }
+
+    //  Optimisation for the case when there's only a single pipe
+    //  to send the message to - no refcount adjustment i.e. no atomic
+    //  operations are needed.
+    if (pipes_count == 1) {
+        out_pipes.begin ()->first->write (msg_);
+        if (flush_)
+            out_pipes.begin ()->first->flush ();
+        int rc = zmq_msg_init (msg_);
+        zmq_assert (rc == 0);
+        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 -1).
+    if (msg_->shared)
+        content->refcnt.add (pipes_count - 1);
+    else {
+        content->refcnt.set (pipes_count);
+        msg_->shared = true;
+    }
+
+    //  Push the message to all destinations.
+    for (out_pipes_t::iterator it = out_pipes.begin (); it != out_pipes.end ();
+          it++) {
+        it->first->write (msg_);
+        if (flush_)
+            it->first->flush ();
+    }
+
+    //  Detach the original message from the data buffer.
+    int rc = zmq_msg_init (msg_);
+    zmq_assert (rc == 0);
+
+    return true;
+}
+
+bool zmq::socket_base_t::fetch (zmq_msg_t *msg_)
+{
+    //  Deallocate old content of the message.
+    zmq_msg_close (msg_);
+
+    //  Round-robin over the pipes to get next message.
+    for (int count = active; count != 0; count--) {
+
+        bool fetched = in_pipes [current].first->read (msg_);
+
+        //  If there's no message in the pipe, move it to the list of
+        //  non-active pipes.
+        if (!fetched) {
+            in_pipes [current].first->set_index (active - 1);
+            in_pipes [active - 1].first->set_index (current);
+            std::swap (in_pipes [current], in_pipes [active - 1]);
+            active--;
+        }
+
+        current ++;
+        if (current >= active)
+            current = 0;
+
+        if (fetched)
+            return true;
+    }
+
+    //  No message is available. Initialise the output parameter
+    //  to be a 0-byte message.
+    zmq_msg_init (msg_);
+    return false;
+}
diff --git a/src/socket_base.hpp b/src/socket_base.hpp
index 20ac4e2..1f04bda 100644
--- a/src/socket_base.hpp
+++ b/src/socket_base.hpp
@@ -22,8 +22,11 @@
 
 #include <set>
 #include <map>
+#include <vector>
 #include <string>
+#include <utility>
 
+#include "i_endpoint.hpp"
 #include "object.hpp"
 #include "mutex.hpp"
 #include "options.hpp"
@@ -32,7 +35,7 @@
 namespace zmq
 {
 
-    class socket_base_t : public object_t
+    class socket_base_t : public object_t, public i_endpoint
     {
     public:
 
@@ -57,22 +60,59 @@ namespace zmq
         bool unregister_session (const char *name_);
         class session_t *find_session (const char *name_);
 
+        //  i_endpoint interface implementation.
+        void revive (class reader_t *pipe_);
+
     private:
 
         //  Handlers for incoming commands.
         void process_own (class owned_t *object_);
+        void process_bind (class owned_t *session_,
+            class reader_t *in_pipe_, class writer_t *out_pipe_);
         void process_term_req (class owned_t *object_);
         void process_term_ack ();
 
+        //  Attempts to distribute the message to all the outbound pipes.
+        //  Returns false if not possible because of pipe overflow.
+        bool distribute (struct zmq_msg_t *msg_, bool flush_);
+
+        //  Gets a message from one of the inbound pipes. Implementation of
+        //  fair queueing.
+        bool fetch (struct zmq_msg_t *msg_);
+
         //  List of all I/O objects owned by this socket. The socket is
         //  responsible for deallocating them before it quits.
         typedef std::set <class owned_t*> io_objects_t;
         io_objects_t io_objects;
 
+        //  Inbound pipes, i.e. those the socket is getting messages from.
+        //  The second member in the pair indicates the object on the other
+        //  side of the pipe.
+        typedef std::vector <std::pair <class reader_t*, owned_t*> >
+            in_pipes_t;
+        in_pipes_t in_pipes;
+
+        //  Index of the next inbound pipe to read messages from.
+        in_pipes_t::size_type current;
+
+        //  Number of active inbound pipes. Active pipes are stored in the
+        //  initial section of the in_pipes array.
+        in_pipes_t::size_type active;
+
+        //  Outbound pipes, i.e. those the socket is sending messages to.
+        //  The second member in the pair indicates the object on the other
+        //  side of the pipe.
+        typedef std::vector <std::pair <class writer_t*, owned_t*> >
+            out_pipes_t;
+        out_pipes_t out_pipes;
+
         //  Number of I/O objects that were already asked to terminate
         //  but haven't acknowledged it yet.
         int pending_term_acks;
 
+        //  Number of messages received since last command processing.
+        int ticks;
+
         //  Application thread the socket lives in.
         class app_thread_t *app_thread;
 
diff --git a/src/ypipe.hpp b/src/ypipe.hpp
index 01b4137..6c51b63 100644
--- a/src/ypipe.hpp
+++ b/src/ypipe.hpp
@@ -43,9 +43,9 @@ namespace zmq
     {
     public:
 
-        //  Initialises the pipe. If 'dead' is set to true, the pipe is
-        //  created in dead state.
-        inline ypipe_t (bool dead_ = true) :
+        //  Initialises the pipe. In D scenario it is created in dead state.
+        //  Otherwise it's alive.
+        inline ypipe_t () :
             stop (false)
         {
             //  Insert terminator element into the queue.
@@ -54,7 +54,7 @@ namespace zmq
             //  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 ());
+            c.set (D ? NULL : &queue.back ());
         }
 
         //  Following function (write) deliberately copies uninitialised data
@@ -110,7 +110,7 @@ namespace zmq
         //  available.
         inline bool read (T *value_)
         {
-            //  Was the value was prefetched already? If so, return it.
+            //  Was the value prefetched already? If so, return it.
             if (&queue.front () != r) {
                  *value_ = queue.front ();
                  queue.pop ();
@@ -159,14 +159,14 @@ namespace zmq
 
                 //  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.
+                //  it can happen during pipe shutdown when messages
+                //  are being deallocated.
                 if (&queue.front () == r || !r)
                     return false;
             }
 
-            //  There was at least one value prefetched -
-            //  return it to the caller.
+            //  There was at least one value prefetched.
+            //  Return it to the caller.
             *value_ = queue.front ();
             queue.pop ();
             return true;
@@ -188,8 +188,8 @@ namespace zmq
         //  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,
+        //  The single 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;
diff --git a/src/yqueue.hpp b/src/yqueue.hpp
index 0686f07..f20ac4c 100644
--- a/src/yqueue.hpp
+++ b/src/yqueue.hpp
@@ -88,7 +88,7 @@ namespace zmq
             back_chunk = end_chunk;
             back_pos = end_pos;
 
-            if (++ end_pos != N)
+            if (++end_pos != N)
                 return;
 
             end_chunk->next = new chunk_t;
diff --git a/src/zmq_encoder.cpp b/src/zmq_encoder.cpp
index 124d77b..39b7192 100644
--- a/src/zmq_encoder.cpp
+++ b/src/zmq_encoder.cpp
@@ -54,9 +54,9 @@ bool zmq::zmq_encoder_t::message_ready ()
     //  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)) {
+    if (!source->read (&in_progress))
         return false;
-    }
+
     size_t size = zmq_msg_size (&in_progress);
 
     //  For messages less than 255 bytes long, write one byte of message size.
diff --git a/src/zmq_engine.cpp b/src/zmq_engine.cpp
index d8b8cfc..cd7ad7e 100644
--- a/src/zmq_engine.cpp
+++ b/src/zmq_engine.cpp
@@ -129,7 +129,12 @@ void zmq::zmq_engine_t::out_event ()
     }
 }
 
+void zmq::zmq_engine_t::revive ()
+{
+    set_pollout (handle);
+}
+
 void zmq::zmq_engine_t::error ()
 {
-//    zmq_assert (false);
+    zmq_assert (false);
 }
diff --git a/src/zmq_engine.hpp b/src/zmq_engine.hpp
index 38a390d..ba25ded 100644
--- a/src/zmq_engine.hpp
+++ b/src/zmq_engine.hpp
@@ -42,6 +42,10 @@ namespace zmq
         void in_event ();
         void out_event ();
 
+        //  This method is called by the session to signalise that there
+        //  are messages to send available.
+        void revive ();
+
     private:
 
         //  Function to handle network disconnections.
diff --git a/src/zmq_listener_init.cpp b/src/zmq_listener_init.cpp
index bfd79b4..7e2f311 100644
--- a/src/zmq_listener_init.cpp
+++ b/src/zmq_listener_init.cpp
@@ -59,7 +59,8 @@ bool zmq::zmq_listener_init_t::write (::zmq_msg_t *msg_)
     session_t *session = owner->find_session (session_name.c_str ());
     if (!session) {
         io_thread_t *io_thread = choose_io_thread (options.affinity);
-        session = new session_t (io_thread, owner, session_name.c_str ());
+        session = new session_t (io_thread, owner, session_name.c_str (),
+            options);
         zmq_assert (session);
         send_plug (session);
         send_own (owner, session);