Perform hostname resolution in caller thread

This change should decrease the latency with which a subscriber socket
connects to its publisher, hopefully making the system more stable.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

daliuge-runtime/dlg/manager/node_manager.py

@@ -369,7 +369,7 @@ def publish_event(self, evt):
     def subscribe(self, host, port):
         timeout = 5
         finished_evt = threading.Event()
-        endpoint = "tcp://%s:%d" % (host, port)
+        endpoint = "tcp://%s:%d" % (utils.zmq_safe(host), port)
         self._subscriptions.put(ZMQPubSubMixIn.subscription(endpoint, finished_evt))
         if not finished_evt.wait(timeout):
             raise DaliugeException("ZMQ subscription not achieved within %d seconds" % (timeout,))