handle XPUB socket type in kernel protocol

Author: minrk

ipyparallel/engine/app.py

@@ -6,6 +6,7 @@
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 import asyncio
+import inspect
 import json
 import os
 import signal
@@ -17,6 +18,7 @@
 
 import ipykernel
 import zmq
+from ipykernel.iostream import IOPubThread
 from ipykernel.kernelapp import IPKernelApp
 from ipykernel.zmqshell import ZMQInteractiveShell
 from IPython.core.profiledir import ProfileDir
@@ -667,17 +669,18 @@ def urls(key):
 
             # create iopub stream:
             iopub_addr = url('iopub')
-            iopub_socket = self.iopub_socket = ctx.socket(zmq.PUB)
+            thread_params = {}
+            if 'session' in inspect.signature(IOPubThread).parameters:
+                iopub_socket_type = zmq.XPUB
+                thread_params["session"] = self.session
+            else:
+                iopub_socket_type = zmq.PUB
+            iopub_socket = self.iopub_socket = ctx.socket(iopub_socket_type)
             iopub_socket.SNDHWM = 0
             iopub_socket.setsockopt(zmq.IDENTITY, identity)
             connect(iopub_socket, iopub_addr)
-            try:
-                from ipykernel.iostream import IOPubThread
-            except ImportError:
-                pass
-            else:
-                iopub_socket = IOPubThread(iopub_socket)
-                iopub_socket.start()
+            iopub_socket = IOPubThread(iopub_socket, **thread_params)
+            iopub_socket.start()
 
             # disable history:
             self.config.HistoryManager.hist_file = ':memory:'