Deliver notification info

Created by: stefanoborini

Notification system to communicate to the UI and other entities interested in notification.

force_bdss/core_plugins/dummy/ui_notification/ui_notification.py

+import errno
+import logging
 from traits.api import Any, List
 
 from force_bdss.api import BaseNotificationListener
@@ -5,17 +7,30 @@ import zmq
 
 
 class UINotification(BaseNotificationListener):
+    #: The ZMQ context.
     _context = Any()
+
+    #: The pubsub socket.
     _pub_socket = Any()
+
+    #: The synchronization socket to recover already sent information at a
+    #: later stage
     _rep_socket = Any()
+
+    #: The cache of messages as they are sent out.
     _msg_cache = List()
 
     def deliver(self, model, message):
         try:
             data = self._rep_socket.recv(flags=zmq.NOBLOCK)
-        except zmq.ZMQError:
-            pass
-        else:
+        except zmq.ZMQError as e:
+            if e.errno == errno.EAGAIN:
+                data = None
+            else:
+                logging.error("Error while receiving data from "
+                              "reply socket: {}".format(str(e)))
+
+        if data and data[0:4] == "SYNC".encode("utf-8"):
             self._rep_socket.send_multipart(self._msg_cache)
 
         msg = "ACTION {}".format(message).encode("utf-8")