New connect_request message type added.

IPython/zmq/entry_point.py

@@ -97,7 +97,8 b' def make_kernel(namespace, kernel_factory,'
 
     hb = Heartbeat(context, (namespace.ip, namespace.hb))
     hb.start()
-    io.raw_print("Heartbeat REP Channel on port", hb.port)
+    hb_port = hb.port
+    io.raw_print("Heartbeat REP Channel on port", hb_port)
 
     # Redirect input streams and set a display hook.
     if out_stream_factory:
@@ -107,8 +108,11 b' def make_kernel(namespace, kernel_factory,'
         sys.displayhook = display_hook_factory(session, pub_socket)
 
     # Create the kernel.
-    return kernel_factory(session=session, reply_socket=reply_socket, 
-                          pub_socket=pub_socket, req_socket=req_socket)
+    kernel = kernel_factory(session=session, reply_socket=reply_socket, 
+                            pub_socket=pub_socket, req_socket=req_socket)
+    kernel.record_ports(xrep_port=xrep_port, pub_port=pub_port,
+                        req_port=req_port, hb_port=hb_port)
+    return kernel
 
 
 def start_kernel(namespace, kernel):

IPython/zmq/ipkernel.py

@@ -75,6 +75,10 b' class Kernel(Configurable):'
     # the end of our shutdown process (which happens after the underlying
     # IPython shell's own shutdown).
     _shutdown_message = None
+
+    # This is a dict of port number that the kernel is listening on. It is set
+    # by record_ports and used by connect_request.
+    _recorded_ports = None
     
     def __init__(self, **kwargs):
         super(Kernel, self).__init__(**kwargs)
@@ -143,7 +147,20 b' class Kernel(Configurable):'
         while True:
             time.sleep(self._poll_interval)
             self.do_one_iteration()
-        
+
+    def record_ports(self, xrep_port, pub_port, req_port, hb_port):
+        """Record the ports that this kernel is using.
+
+        The creator of the Kernel instance must call this methods if they
+        want the :meth:`connect_request` method to return the port numbers.
+        """
+        self._recorded_ports = {
+            'xrep_port' : xreq_port,
+            'pub_port' : pub_port,
+            'req_port' : req_port,
+            'hb_port' : hb_port
+        }
+
     #---------------------------------------------------------------------------
     # Kernel request handlers
     #---------------------------------------------------------------------------
@@ -287,12 +304,21 b' class Kernel(Configurable):'
         msg = self.session.send(self.reply_socket, 'history_reply',
                                 content, parent, ident)
         io.raw_print(msg)
-        
+
+    def connect_request(self, ident, parent):
+        if self._recorded_ports is not None:
+            content = self._recorded_ports.copy()
+        else:
+            content = {}
+        msg = self.session.send(self.reply_socket, 'connect_reply',
+                                content, parent, ident)
+        io.raw_print(msg)
+
     def shutdown_request(self, ident, parent):
         self.shell.exit_now = True
         self._shutdown_message = self.session.msg(u'shutdown_reply', {}, parent)
         sys.exit(0)
-        
+
     #---------------------------------------------------------------------------
     # Protected interface
     #---------------------------------------------------------------------------

docs/source/development/messaging.txt

@@ -536,6 +536,30 b' Message type: ``history_reply``::'
     }
 
 
+Connect
+-------
+
+When a client connects to the request/reply socket of the kernel, it can issue
+a connect request to get basic information about the kernel, such as the ports
+the other ZeroMQ sockets are listening on. This allows clients to only have
+to know about a single port (the XREQ/XREP channel) to connect to a kernel.
+
+Message type: ``connect_request``::
+
+    content = {
+    }
+
+Message type: ``connect_reply``::
+
+    content = {
+        'xrep_port' : int  # The port the XREP socket is listening on.
+        'pub_port' : int   # The port the PUB socket is listening on.
+        'req_port' : int   # The port the REQ socket is listening on.
+        'hb_port' : int    # The port the heartbeat socket is listening on.
+    }
+
+
+
 Kernel shutdown
 ---------------