lockfree interaction patter for 3 theads implemented

20 files changed, 569 insertions, 268 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index bde9c39..47037a2 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -7,14 +7,15 @@ libzmq_la_SOURCES = \
     atomic_ptr.hpp \
     command.hpp \
     config.hpp \
-    context.hpp \
     decoder.hpp \
     devpoll.hpp \
+    dispatcher.hpp \
     encoder.hpp \
     epoll.hpp \
     err.hpp \
     fd.hpp \
     fd_signaler.hpp \
+    io_object.hpp \
     io_thread.hpp \
     ip.hpp \
     i_api.hpp \
@@ -31,6 +32,7 @@ libzmq_la_SOURCES = \
     poll.hpp \
     select.hpp \
     simple_semaphore.hpp \
+    socket_base.hpp \
     stdint.hpp \
     tcp_connecter.hpp \
     tcp_listener.hpp \
@@ -42,25 +44,29 @@ libzmq_la_SOURCES = \
     ypipe.hpp \
     ypollset.hpp \
     yqueue.hpp \
+    zmq_listener.hpp \
     app_thread.cpp \
-    context.cpp \
-    devpoll.hpp \
+    devpoll.cpp \
+    dispatcher.cpp \
     epoll.cpp \
     err.cpp \
     fd_signaler.cpp \
+    io_object.cpp \
     io_thread.cpp \
     ip.cpp \
     kqueue.cpp \
     object.cpp \
     poll.cpp \
     select.cpp \
+    socket_base.cpp \
     tcp_connecter.cpp \
     tcp_listener.cpp \
     tcp_socket.cpp \
     thread.cpp \
     uuid.cpp \
     ypollset.cpp \
-    zmq.cpp
+    zmq.cpp \
+    zmq_listener.cpp
 
 libzmq_la_LDFLAGS = -version-info 0:0:0
 libzmq_la_CXXFLAGS = -Wall -pedantic -Werror @ZMQ_EXTRA_CXXFLAGS@
diff --git a/src/app_thread.cpp b/src/app_thread.cpp
index 23a055a..3f76970 100644
--- a/src/app_thread.cpp
+++ b/src/app_thread.cpp
@@ -17,6 +17,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <algorithm>
+
 #include "../include/zmq.h"
 
 #if defined ZMQ_HAVE_WINDOWS
@@ -26,10 +28,12 @@
 #endif
 
 #include "app_thread.hpp"
-#include "context.hpp"
+#include "i_api.hpp"
+#include "dispatcher.hpp"
 #include "err.hpp"
 #include "pipe.hpp"
 #include "config.hpp"
+#include "socket_base.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
@@ -39,8 +43,8 @@
 #define ZMQ_DELAY_COMMANDS
 #endif
 
-zmq::app_thread_t::app_thread_t (context_t *context_, int thread_slot_) :
-    object_t (context_, thread_slot_),
+zmq::app_thread_t::app_thread_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    object_t (dispatcher_, thread_slot_),
     tid (0),
     last_processing_time (0)
 {
@@ -48,13 +52,9 @@ zmq::app_thread_t::app_thread_t (context_t *context_, int thread_slot_) :
 
 zmq::app_thread_t::~app_thread_t ()
 {
-    //  Ask all the sockets to start termination, then wait till it is complete.
-    for (sockets_t::iterator it = sockets.begin (); it != sockets.end (); it ++)
-        (*it)->stop ();
+    //  Destroy all the sockets owned by this application thread.
     for (sockets_t::iterator it = sockets.begin (); it != sockets.end (); it ++)
         delete *it;
-
-    delete this;
 }
 
 zmq::i_signaler *zmq::app_thread_t::get_signaler ()
@@ -123,9 +123,28 @@ void zmq::app_thread_t::process_commands (bool block_)
         for (int i = 0; i != thread_slot_count (); i++) {
             if (signals & (ypollset_t::signals_t (1) << i)) {
                 command_t cmd;
-                while (context->read (i, get_thread_slot (), &cmd))
+                while (dispatcher->read (i, get_thread_slot (), &cmd))
                     cmd.destination->process_command (cmd);
             }
         }
     }
 }
+
+zmq::i_api *zmq::app_thread_t::create_socket (int type_)
+{
+    //  TODO: type is ignored for the time being.
+    socket_base_t *s = new socket_base_t (this);
+    zmq_assert (s);
+    sockets.push_back (s);
+    return s;
+}
+
+void zmq::app_thread_t::remove_socket (i_api *socket_)
+{
+    //  TODO: To speed this up we can possibly use the system where each socket
+    //        holds its index (see I/O scheduler implementation).
+    sockets_t::iterator it = std::find (sockets.begin (), sockets.end (),
+        socket_);
+    zmq_assert (it != sockets.end ());
+    sockets.erase (it);
+}
diff --git a/src/app_thread.hpp b/src/app_thread.hpp
index 31679b8..59e4a25 100644
--- a/src/app_thread.hpp
+++ b/src/app_thread.hpp
@@ -22,7 +22,6 @@
 
 #include <vector>
 
-#include "i_socket.hpp"
 #include "stdint.hpp"
 #include "object.hpp"
 #include "ypollset.hpp"
@@ -34,7 +33,7 @@ namespace zmq
     {
     public:
 
-        app_thread_t (class context_t *context_, int thread_slot_);
+        app_thread_t (class dispatcher_t *dispatcher_, int thread_slot_);
 
         ~app_thread_t ();
 
@@ -42,7 +41,7 @@ namespace zmq
         i_signaler *get_signaler ();
 
         //  Nota bene: Following two functions are accessed from different
-        //  threads. The caller (context) is responsible for synchronisation
+        //  threads. The caller (dispatcher) is responsible for synchronisation
         //  of accesses.
 
         //  Returns true is current thread is associated with the app thread.
@@ -56,10 +55,16 @@ namespace zmq
         //  set to true, returns only after at least one command was processed.
         void process_commands (bool block_);
 
+        //  Create a socket of a specified type.
+        struct i_api *create_socket (int type_);
+
+        //  Unregister the socket from the app_thread (called by socket itself).
+        void remove_socket (struct i_api *socket_);
+
     private:
 
         //  All the sockets created from this application thread.
-        typedef std::vector <i_socket*> sockets_t;
+        typedef std::vector <struct i_api*> sockets_t;
         sockets_t sockets;
 
         //  Thread ID associated with this slot.
diff --git a/src/command.hpp b/src/command.hpp
index 69c4e57..de94ca3 100644
--- a/src/command.hpp
+++ b/src/command.hpp
@@ -35,60 +35,49 @@ namespace zmq
         enum type_t
         {
             stop,
+            plug,
+            own,
             bind,
-            head,
-            tail,
-            reg,
-            reg_and_bind,
-            unreg,
-            engine,
-            terminate,
-            terminate_ack
+            term_req,
+            term,
+            term_ack
+
         } type;
 
         union {
 
+            //  Sent to I/O thread to let it know that it should
+            //  terminate itself.
             struct {
             } stop;
 
+            //  Sent to I/O object to make it register with its I/O thread.
             struct {
-                class pipe_reader_t *reader;
-                class session_t *peer;
-            } bind;
+            } plug;
 
+            //  Sent to socket to let it know about the newly created object.
             struct {
-                uint64_t bytes;
-            } tail;
+                class object_t *object;
+            } own;
 
+            //  Sent between objects to establish pipe(s) between them.
             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;
+            } bind;
 
-            //  TODO: Engine object won't be deallocated on terminal shutdown
-            //  while the command is still on the fly!
+            //  Sent by I/O object ot the socket to request the shutdown of
+            //  the I/O object.
             struct {
-                class i_engine *engine;
-            } engine;
+                class object_t *object;
+            } term_req;
 
+            //  Sent by socket to I/O object to start its shutdown.
             struct {
-            } terminate;
+            } term;
 
+            //  Sent by I/O object to the socket to acknowledge it has
+            //  shut down.
             struct {
-            } terminate_ack;
+            } term_ack;
 
         } args;
     };
diff --git a/src/context.cpp b/src/dispatcher.cpp
index 6b071cf..0b68880 100644
--- a/src/context.cpp
+++ b/src/dispatcher.cpp
@@ -19,7 +19,7 @@
 
 #include "../include/zmq.h"
 
-#include "context.hpp"
+#include "dispatcher.hpp"
 #include "i_api.hpp"
 #include "app_thread.hpp"
 #include "io_thread.hpp"
@@ -31,7 +31,7 @@
 #include "windows.h"
 #endif
 
-zmq::context_t::context_t (int app_threads_, int io_threads_)
+zmq::dispatcher_t::dispatcher_t (int app_threads_, int io_threads_)
 {
 #ifdef ZMQ_HAVE_WINDOWS
     //  Intialise Windows sockets. Note that WSAStartup can be called multiple
@@ -69,7 +69,7 @@ zmq::context_t::context_t (int app_threads_, int io_threads_)
         io_threads [i]->start ();
 }
 
-zmq::context_t::~context_t ()
+zmq::dispatcher_t::~dispatcher_t ()
 {
     //  Close all application theads, sockets, io_objects etc.
     for (app_threads_t::size_type i = 0; i != app_threads.size (); i++)
@@ -93,12 +93,12 @@ zmq::context_t::~context_t ()
 #endif
 }
 
-int zmq::context_t::thread_slot_count ()
+int zmq::dispatcher_t::thread_slot_count ()
 {
     return signalers.size ();
 }
 
-zmq::i_api *zmq::context_t::create_socket (int type_)
+zmq::i_api *zmq::dispatcher_t::create_socket (int type_)
 {
     threads_sync.lock ();
     app_thread_t *thread = choose_app_thread ();
@@ -106,16 +106,12 @@ zmq::i_api *zmq::context_t::create_socket (int type_)
         threads_sync.unlock ();
         return NULL;
     }
-
-    zmq_assert (false);
-    i_api *s = NULL;
-    //i_api *s = thread->create_socket (type_);
-
     threads_sync.unlock ();
-    return s;
+
+    return thread->create_socket (type_);
 }
 
-zmq::app_thread_t *zmq::context_t::choose_app_thread ()
+zmq::app_thread_t *zmq::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++)
@@ -132,7 +128,7 @@ zmq::app_thread_t *zmq::context_t::choose_app_thread ()
     return NULL;
 }
 
-zmq::io_thread_t *zmq::context_t::choose_io_thread (uint64_t taskset_)
+zmq::io_thread_t *zmq::dispatcher_t::choose_io_thread (uint64_t taskset_)
 {
     zmq_assert (io_threads.size () > 0);
 
diff --git a/src/context.hpp b/src/dispatcher.hpp
index f2eab1c..08ffab1 100644
--- a/src/context.hpp
+++ b/src/dispatcher.hpp
@@ -17,8 +17,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef __ZMQ_CONTEXT_HPP_INCLUDED__
-#define __ZMQ_CONTEXT_HPP_INCLUDED__
+#ifndef __ZMQ_DISPATCHER_HPP_INCLUDED__
+#define __ZMQ_DISPATCHER_HPP_INCLUDED__
 
 #include <vector>
 #include <map>
@@ -37,27 +37,27 @@ namespace zmq
     //  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 context is inefficient for passing messages
+    //  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 context_t
+    class dispatcher_t
     {
     public:
 
-        //  Create the context object. Matrix of pipes to communicate between
+        //  Create the dispatcher object. Matrix of pipes to communicate between
         //  each socket and each I/O thread is created along with appropriate
         //  signalers.
-        context_t (int app_threads_, int io_threads_);
+        dispatcher_t (int app_threads_, int io_threads_);
 
         //  To be called to terminate the whole infrastructure (zmq_term).
-        ~context_t ();
+        ~dispatcher_t ();
 
         //  Create a socket.
         struct i_api *create_socket (int type_);
 
-        //  Returns number of thread slots in the context. To be used by
+        //  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 ();
@@ -112,8 +112,8 @@ namespace zmq
         //  Synchronisation of accesses to shared thread data.
         mutex_t threads_sync;
 
-        context_t (const context_t&);
-        void operator = (const context_t&);
+        dispatcher_t (const dispatcher_t&);
+        void operator = (const dispatcher_t&);
     };
     
 }
diff --git a/src/err.hpp b/src/err.hpp
index fdfce01..3854d8a 100644
--- a/src/err.hpp
+++ b/src/err.hpp
@@ -80,6 +80,12 @@ namespace zmq
     abort ();\
 }} while (false)
 
+// Provides convenient way to check for POSIX errors.
+#define posix_assert(x) do {\
+fprintf (stderr, "%s (%s:%d)\n", strerror (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);\
diff --git a/src/i_api.hpp b/src/i_api.hpp
index a87e41d..36afcea 100644
--- a/src/i_api.hpp
+++ b/src/i_api.hpp
@@ -1,20 +1,20 @@
 /*
-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/>.
+    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_API_HPP_INCLUDED__
@@ -25,6 +25,8 @@ namespace zmq
  
     struct i_api
     {
+        virtual ~i_api () {}
+
         virtual int bind (const char *addr_, struct zmq_opts *opts_) = 0;
         virtual int connect (const char *addr_, struct zmq_opts *opts_) = 0;
         virtual int subscribe (const char *criteria_) = 0;
diff --git a/src/io_object.cpp b/src/io_object.cpp
new file mode 100644
index 0000000..41e4717
--- /dev/null
+++ b/src/io_object.cpp
@@ -0,0 +1,41 @@
+/*
+    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"
+
+zmq::io_object_t::io_object_t (object_t *parent_, object_t *owner_) :
+    object_t (parent_),
+    owner (owner_)
+{
+}
+
+zmq::io_object_t::~io_object_t ()
+{
+}
+
+void zmq::io_object_t::term ()
+{
+    send_term_req (owner, this);
+}
+
+void zmq::io_object_t::process_term ()
+{
+    send_term_ack (owner);
+    delete this;
+}
diff --git a/src/io_object.hpp b/src/io_object.hpp
new file mode 100644
index 0000000..5ed1830
--- /dev/null
+++ b/src/io_object.hpp
@@ -0,0 +1,62 @@
+/*
+    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_IO_OBJECT_HPP_INCLUDED__
+#define __ZMQ_IO_OBJECT_HPP_INCLUDED__
+
+#include "object.hpp"
+
+namespace zmq
+{
+
+    class io_object_t : public object_t
+    {
+    public:
+
+        //  I/O object will live in the thread inherited from the parent.
+        //  However, it's lifetime is managed by the owner.
+        io_object_t (object_t *parent_, object_t *owner_);
+
+    protected:
+
+        //  Ask owner socket to terminate this I/O object. This may not happen
+        void term ();
+
+        //  I/O object destroys itself. No point in allowing others to invoke
+        //  the destructor. At the same time, it has to be virtual so that
+        //  generic io_object deallocation mechanism destroys specific type
+        //  of I/O object correctly.
+        virtual ~io_object_t ();
+
+    private:
+
+        //  Handlers for incoming commands.
+        void process_term ();
+
+        //  Socket owning this I/O object. It is responsible for destroying
+        //  it when it's being closed.
+        object_t *owner;
+
+        io_object_t (const io_object_t&);
+        void operator = (const io_object_t&);
+    };
+
+}
+
+#endif
diff --git a/src/io_thread.cpp b/src/io_thread.cpp
index f5261a6..1d85292 100644
--- a/src/io_thread.cpp
+++ b/src/io_thread.cpp
@@ -29,11 +29,11 @@
 #include "select.hpp"
 #include "devpoll.hpp"
 #include "kqueue.hpp"
-#include "context.hpp"
+#include "dispatcher.hpp"
 #include "simple_semaphore.hpp"
 
-zmq::io_thread_t::io_thread_t (context_t *context_, int thread_slot_) :
-    object_t (context_, thread_slot_)
+zmq::io_thread_t::io_thread_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    object_t (dispatcher_, thread_slot_)
 {
 #if defined ZMQ_FORCE_SELECT
     poller = new select_t;
@@ -115,7 +115,7 @@ void zmq::io_thread_t::in_event ()
 
             //  Read all the commands from particular thread.
             command_t cmd;
-            while (context->read (source_thread_slot, thread_slot, &cmd))
+            while (dispatcher->read (source_thread_slot, thread_slot, &cmd))
                 cmd.destination->process_command (cmd);
         }
     }
diff --git a/src/io_thread.hpp b/src/io_thread.hpp
index 43ee19e..6f25627 100644
--- a/src/io_thread.hpp
+++ b/src/io_thread.hpp
@@ -37,7 +37,7 @@ namespace zmq
     {
     public:
 
-        io_thread_t (class context_t *context_, int thread_slot_);
+        io_thread_t (class dispatcher_t *dispatcher_, int thread_slot_);
 
         //  Clean-up. If the thread was started, it's neccessary to call 'stop'
         //  before invoking destructor. Otherwise the destructor would hang up.
diff --git a/src/mutex.hpp b/src/mutex.hpp
index 9b51955..e233c9e 100644
--- a/src/mutex.hpp
+++ b/src/mutex.hpp
@@ -72,43 +72,47 @@ namespace zmq
 
 namespace zmq
 {
-
+ 
     class mutex_t
     {
     public:
         inline mutex_t ()
         {
             int rc = pthread_mutex_init (&mutex, NULL);
-            errno_assert (rc == 0);
+            if (rc)
+                posix_assert (rc);
         }
-
+ 
         inline ~mutex_t ()
         {
             int rc = pthread_mutex_destroy (&mutex);
-            errno_assert (rc == 0);
+            if (rc)
+                posix_assert (rc);
         }
-
+ 
         inline void lock ()
         {
             int rc = pthread_mutex_lock (&mutex);
-            errno_assert (rc == 0);
+            if (rc)
+                posix_assert (rc);
         }
-
+ 
         inline void unlock ()
         {
             int rc = pthread_mutex_unlock (&mutex);
-            errno_assert (rc == 0);
+            if (rc)
+                posix_assert (rc);
         }
-
+ 
     private:
-
+ 
         pthread_mutex_t mutex;
-
-        //  Disable copy construction and assignment.
+ 
+        // Disable copy construction and assignment.
         mutex_t (const mutex_t&);
         void operator = (const mutex_t&);
     };
-
+ 
 }
 
 #endif
diff --git a/src/object.cpp b/src/object.cpp
index 36f3937..e2267d6 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -18,19 +18,19 @@
 */
 
 #include "object.hpp"
-#include "context.hpp"
+#include "dispatcher.hpp"
 #include "err.hpp"
 #include "io_thread.hpp"
 #include "simple_semaphore.hpp"
 
-zmq::object_t::object_t (context_t *context_, int thread_slot_) :
-    context (context_),
+zmq::object_t::object_t (dispatcher_t *dispatcher_, int thread_slot_) :
+    dispatcher (dispatcher_),
     thread_slot (thread_slot_)
 {
 }
 
 zmq::object_t::object_t (object_t *parent_) :
-    context (parent_->context),
+    dispatcher (parent_->dispatcher),
     thread_slot (parent_->thread_slot)
 {
 }
@@ -41,7 +41,7 @@ zmq::object_t::~object_t ()
 
 int zmq::object_t::thread_slot_count ()
 {
-    return context->thread_slot_count ();
+    return dispatcher->thread_slot_count ();
 }
 
 int zmq::object_t::get_thread_slot ()
@@ -53,45 +53,32 @@ void zmq::object_t::process_command (command_t &cmd_)
 {
     switch (cmd_.type) {
 
-    case command_t::head:
-        process_head (cmd_.args.head.bytes);
+    case command_t::stop:
+        process_stop ();
         break;
 
-    case command_t::tail:
-        process_tail (cmd_.args.tail.bytes);
-        break;
+    case command_t::plug:
+        process_plug ();
+        return;
 
-    case command_t::engine:
-        process_engine (cmd_.args.engine.engine);
-        break;
+    case command_t::own:
+        process_own (cmd_.args.own.object);
+        return;
 
     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;
+        process_bind ();
+        return;
 
-    case command_t::terminate_ack:
-        process_terminate_ack ();
-        break;
+    case command_t::term_req:
+        process_term_req (cmd_.args.term_req.object);
+        return;
+    
+    case command_t::term:
+        process_term ();
+        return;
 
-    case command_t::stop:
-        process_stop ();
+    case command_t::term_ack:
+        process_term_ack ();
         return;
 
     default:
@@ -101,7 +88,7 @@ void zmq::object_t::process_command (command_t &cmd_)
 
 zmq::io_thread_t *zmq::object_t::choose_io_thread (uint64_t taskset_)
 {
-    return context->choose_io_thread (taskset_);
+    return dispatcher->choose_io_thread (taskset_);
 }
 
 void zmq::object_t::send_stop ()
@@ -111,91 +98,56 @@ void zmq::object_t::send_stop ()
     command_t cmd;
     cmd.destination = this;
     cmd.type = command_t::stop;
-    context->write (thread_slot, thread_slot, cmd);
+    dispatcher->write (thread_slot, thread_slot, cmd);
 }
 
-void zmq::object_t::send_bind (object_t *destination_, pipe_reader_t *reader_,
-    session_t *peer_)
+void zmq::object_t::send_plug (object_t *destination_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::bind;
-    cmd.args.bind.reader = reader_;
-    cmd.args.bind.peer = peer_;
+    cmd.type = command_t::plug;
     send_command (cmd);
 }
 
-void zmq::object_t::send_head (object_t *destination_, uint64_t bytes_)
+void zmq::object_t::send_own (object_t *destination_, object_t *object_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::head;
-    cmd.args.head.bytes = bytes_;
+    cmd.type = command_t::own;
+    cmd.args.own.object = object_;
     send_command (cmd);
 }
 
-void zmq::object_t::send_tail (object_t *destination_, uint64_t bytes_)
+void zmq::object_t::send_bind (object_t *destination_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::tail;
-    cmd.args.tail.bytes = bytes_;
-    send_command (cmd);
-}
-
-void zmq::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 zmq::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 zmq::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_;
+    cmd.type = command_t::bind;
     send_command (cmd);
 }
 
-void zmq::object_t::send_engine (object_t *destination_, i_engine *engine_)
+void zmq::object_t::send_term_req (object_t *destination_, object_t *object_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::engine;
-    cmd.args.engine.engine = engine_;
+    cmd.type = command_t::term_req;
+    cmd.args.term_req.object = object_;
     send_command (cmd);
 }
 
-void zmq::object_t::send_terminate (object_t *destination_)
+void zmq::object_t::send_term (object_t *destination_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::terminate;
+    cmd.type = command_t::term;
     send_command (cmd);
 }
 
-void zmq::object_t::send_terminate_ack (object_t *destination_)
+void zmq::object_t::send_term_ack (object_t *destination_)
 {
     command_t cmd;
     cmd.destination = destination_;
-    cmd.type = command_t::terminate_ack;
+    cmd.type = command_t::term_ack;
     send_command (cmd);
 }
 
@@ -204,48 +156,32 @@ void zmq::object_t::process_stop ()
     zmq_assert (false);
 }
 
-void zmq::object_t::process_bind (pipe_reader_t *reader_, session_t *peer_)
-{
-    zmq_assert (false);
-}
-
-void zmq::object_t::process_head (uint64_t bytes_)
-{
-    zmq_assert (false);
-}
-
-void zmq::object_t::process_tail (uint64_t bytes_)
-{
-    zmq_assert (false);
-}
-
-void zmq::object_t::process_reg (simple_semaphore_t *smph_)
+void zmq::object_t::process_plug ()
 {
     zmq_assert (false);
 }
 
-void zmq::object_t::process_reg_and_bind (session_t *session_,
-    bool flow_in_, bool flow_out_)
+void zmq::object_t::process_own (object_t *object_)
 {
     zmq_assert (false);
 }
 
-void zmq::object_t::process_unreg (simple_semaphore_t *smph_)
+void zmq::object_t::process_bind ()
 {
     zmq_assert (false);
 }
 
-void zmq::object_t::process_engine (i_engine *engine_)
+void zmq::object_t::process_term_req (object_t *object_)
 {
     zmq_assert (false);
 }
 
-void zmq::object_t::process_terminate ()
+void zmq::object_t::process_term ()
 {
     zmq_assert (false);
 }
 
-void zmq::object_t::process_terminate_ack ()
+void zmq::object_t::process_term_ack ()
 {
     zmq_assert (false);
 }
@@ -256,6 +192,6 @@ void zmq::object_t::send_command (command_t &cmd_)
     if (destination_thread_slot == thread_slot)
         cmd_.destination->process_command (cmd_);
     else 
-        context->write (thread_slot, destination_thread_slot, cmd_);
+        dispatcher->write (thread_slot, destination_thread_slot, cmd_);
 }
 
diff --git a/src/object.hpp b/src/object.hpp
index 5851c68..7357549 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -32,7 +32,7 @@ namespace zmq
     {
     public:
 
-        object_t (class context_t *context_, int thread_slot_);
+        object_t (class dispatcher_t *dispatcher_, int thread_slot_);
         object_t (object_t *parent_);
         ~object_t ();
 
@@ -42,44 +42,32 @@ namespace zmq
     protected:
 
         //  Derived object can use following functions to interact with
-        //  global repositories. See context.hpp for function details.
+        //  global repositories. See dispatcher.hpp for function details.
         int thread_slot_count ();
         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_);
+        void send_plug (object_t *destination_);
+        void send_own (object_t *destination_, object_t *object_);
+        void send_bind (object_t *destination_);
+        void send_term_req (object_t *destination_, object_t *object_);
+        void send_term (object_t *destination_);
+        void send_term_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 ();
+        virtual void process_plug ();
+        virtual void process_own (object_t *object_);
+        virtual void process_bind ();
+        virtual void process_term_req (object_t *object_);
+        virtual void process_term ();
+        virtual void process_term_ack ();
 
         //  Pointer to the root of the infrastructure.
-        class context_t *context;
+        class dispatcher_t *dispatcher;
 
         //  Slot ID of the thread the object belongs to.
         int thread_slot;
diff --git a/src/socket_base.cpp b/src/socket_base.cpp
new file mode 100644
index 0000000..3737410
--- /dev/null
+++ b/src/socket_base.cpp
@@ -0,0 +1,129 @@
+/*
+    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 <algorithm>
+
+#include "../include/zmq.h"
+
+#include "socket_base.hpp"
+#include "app_thread.hpp"
+#include "err.hpp"
+#include "zmq_listener.hpp"
+#include "io_thread.hpp"
+
+zmq::socket_base_t::socket_base_t (app_thread_t *parent_) :
+    object_t (parent_),
+    pending_term_acks (0),
+    app_thread (parent_)
+{
+}
+
+zmq::socket_base_t::~socket_base_t ()
+{
+    while (true) {
+
+        //  On third pass of the loop there should be no more I/O objects
+        //  because all connecters and listerners were destroyed during
+        //  the first pass and all engines delivered by delayed 'own' commands
+        //  are destroyed during the second pass.
+        if (io_objects.empty () && !pending_term_acks)
+            break;
+
+        //  Send termination request to all associated I/O objects.
+        for (io_objects_t::size_type i = 0; i != io_objects.size (); i++)
+            send_term (io_objects [i]);
+
+        //  Move the objects to the list of pending term acks.
+        pending_term_acks += io_objects.size ();
+        io_objects.clear ();
+
+        //  Process commands till we get all the termination acknowledgements.
+        while (pending_term_acks)
+            app_thread->process_commands (true);
+    }
+}
+
+int zmq::socket_base_t::bind (const char *addr_, struct zmq_opts *opts_)
+{
+    uint64_t taskset = opts_ ? opts_->taskset : 0;
+    object_t *listener = new zmq_listener_t (choose_io_thread (taskset), this);
+    send_plug (listener);
+    send_own (this, listener);
+    return 0;
+}
+
+int zmq::socket_base_t::connect (const char *addr_, struct zmq_opts *opts_)
+{
+    zmq_assert (false);
+}
+
+int zmq::socket_base_t::subscribe (const char *criteria_)
+{
+    zmq_assert (false);
+}
+
+int zmq::socket_base_t::send (struct zmq_msg *msg_, int flags_)
+{
+    zmq_assert (false);
+}
+
+int zmq::socket_base_t::flush ()
+{
+    zmq_assert (false);
+}
+
+int zmq::socket_base_t::recv (struct zmq_msg *msg_, int flags_)
+{
+    zmq_assert (false);
+}
+
+int zmq::socket_base_t::close ()
+{
+    app_thread->remove_socket (this);
+    delete this;
+    return 0;
+}
+
+void zmq::socket_base_t::process_own (object_t *object_)
+{
+    io_objects.push_back (object_);
+}
+
+void zmq::socket_base_t::process_term_req (object_t *object_)
+{
+    //  If I/O object is well and alive ask it to terminate.
+    //  TODO: Following find may produce an unacceptable jitter in
+    //        C10K-style applications. If so, use set instead of vector.
+    io_objects_t::iterator it = std::find (io_objects.begin (),
+        io_objects.end (), object_);
+    if (it != io_objects.end ()) {
+        pending_term_acks++;
+        io_objects.erase (it);
+        send_term (object_);
+    }
+
+    //  If not found, we assume that termination request was already sent to
+    //  the object so we can sagely ignore the request.
+}
+
+void zmq::socket_base_t::process_term_ack ()
+{
+    zmq_assert (pending_term_acks);
+    pending_term_acks--;
+}
diff --git a/src/socket_base.hpp b/src/socket_base.hpp
new file mode 100644
index 0000000..633f003
--- /dev/null
+++ b/src/socket_base.hpp
@@ -0,0 +1,72 @@
+/*
+    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_SOCKET_BASE_HPP_INCLUDED__
+#define __ZMQ_SOCKET_BASE_HPP_INCLUDED__
+
+#include <vector>
+
+#include "i_api.hpp"
+#include "object.hpp"
+
+namespace zmq
+{
+
+    class socket_base_t : public object_t, public i_api
+    {
+    public:
+
+        socket_base_t (class app_thread_t *parent_);
+        ~socket_base_t ();
+
+        //  i_api interface implementation.
+        int bind (const char *addr_, struct zmq_opts *opts_);
+        int connect (const char *addr_, struct zmq_opts *opts_);
+        int subscribe (const char *criteria_);
+        int send (struct zmq_msg *msg_, int flags_);
+        int flush ();
+        int recv (struct zmq_msg *msg_, int flags_);
+        int close ();
+
+    private:
+
+        //  Handlers for incoming commands.
+        void process_own (object_t *object_);
+        void process_term_req (object_t *object_);
+        void process_term_ack ();
+
+        //  List of all I/O objects owned by this socket. The socket is
+        //  responsible for deallocating them before it quits.
+        typedef std::vector <object_t*> io_objects_t;
+        io_objects_t io_objects;
+
+        //  Number of I/O objects that were already asked to terminate
+        //  but haven't acknowledged it yet.
+        int pending_term_acks;
+
+        //  Application thread the socket lives in.
+        class app_thread_t *app_thread;
+
+        socket_base_t (const socket_base_t&);
+        void operator = (const socket_base_t&);
+    };
+
+}
+
+#endif
diff --git a/src/zmq.cpp b/src/zmq.cpp
index d19b229..149a7e2 100644
--- a/src/zmq.cpp
+++ b/src/zmq.cpp
@@ -25,7 +25,7 @@
 
 #include "i_api.hpp"
 #include "err.hpp"
-#include "context.hpp"
+#include "dispatcher.hpp"
 #include "msg.hpp"
 
 int zmq_msg_init (zmq_msg *msg_)
@@ -162,27 +162,28 @@ int zmq_msg_type (zmq_msg *msg_)
 
 void *zmq_init (int app_threads_, int io_threads_)
 {
-    //  There should be at least a single thread managed by the context.
+    //  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;
     }
 
-    zmq::context_t *context = new zmq::context_t (app_threads_, io_threads_);
-    zmq_assert (context);
-    return (void*) context;
+    zmq::dispatcher_t *dispatcher = new zmq::dispatcher_t (app_threads_,
+        io_threads_);
+    zmq_assert (dispatcher);
+    return (void*) dispatcher;
 }
 
-int zmq_term (void *context_)
+int zmq_term (void *dispatcher_)
 {
-    delete (zmq::context_t*) context_;
+    delete (zmq::dispatcher_t*) dispatcher_;
     return 0;
 }
 
-void *zmq_socket (void *context_, int type_)
+void *zmq_socket (void *dispatcher_, int type_)
 {
-    return (void*) (((zmq::context_t*) context_)->create_socket (type_));
+    return (void*) (((zmq::dispatcher_t*) dispatcher_)->create_socket (type_));
 }
 
 int zmq_close (void *s_)
diff --git a/src/i_socket.hpp b/src/zmq_listener.cpp
index 99ade8a..1f1e012 100644
--- a/src/i_socket.hpp
+++ b/src/zmq_listener.cpp
@@ -17,20 +17,19 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef __ZMQ_I_SOCKET_HPP_INCLUDED__
-#define __ZMQ_I_SOCKET_HPP_INCLUDED__
+#include "zmq_listener.hpp"
+#include "err.hpp"
 
-namespace zmq
+zmq::zmq_listener_t::zmq_listener_t (object_t *parent_, object_t *owner_) :
+    io_object_t (parent_, owner_)
 {
+}
 
-    struct i_socket
-    {
-        virtual ~i_socket () {};
-
-        //  Start shutting down the socket.
-        virtual void stop () = 0;
-    };
-
+zmq::zmq_listener_t::~zmq_listener_t ()
+{
 }
 
-#endif
+void zmq::zmq_listener_t::process_plug ()
+{
+    //  TODO:  Register with the I/O thread here.
+}
diff --git a/src/zmq_listener.hpp b/src/zmq_listener.hpp
new file mode 100644
index 0000000..12192b2
--- /dev/null
+++ b/src/zmq_listener.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 __ZMQ_ZMQ_LISTENER_HPP_INCLUDED__
+#define __ZMQ_ZMQ_LISTENER_HPP_INCLUDED__
+
+#include "io_object.hpp"
+
+namespace zmq
+{
+
+    class zmq_listener_t : public io_object_t
+    {
+    public:
+
+        zmq_listener_t (object_t *parent_, object_t *owner_);
+        ~zmq_listener_t ();
+
+    private:
+
+        //  Handlers for incoming commands.
+        void process_plug ();
+
+        zmq_listener_t (const zmq_listener_t&);
+        void operator = (const zmq_listener_t&);
+    };
+
+}
+
+#endif