Use change listener rather than direct message factory for lidar.

tracking/lidar_servicer.py

@@ -4,12 +4,16 @@ from tracking.lidar_cache import LidarCache
 from multiprocessing import Process
 import messaging.message_factory as mf
 from rplidar import RPLidar
+from Messaging import messages
+
 
 class LidarServicer(PersonTrackingServicer):
 
     def __init__(self):
-        #TODO: Put the rplidar creation in a factory or something, to make it possible to test this servicer.
+        # TODO: Put the rplidar creation in a factory or something, to make it possible to test this servicer.
         self.cache = LidarCache(RPLidar('/dev/ttyUSB0'), measurements=100)
+        self._mFactory = None
+        self._port = None
 
     def set_tracking_group(self, request, context):
         pass
@@ -19,4 +23,11 @@ class LidarServicer(PersonTrackingServicer):
 
     def start_tracking(self, request, context):
         """Starts the lidar cache, streaming on the provided port."""
-        self.cache.start_cache(mf.getZmqPubSubStreamer(request.value))
+        self._port = request.value
+        self.cache.start_cache(self)
+
+    def onGroupsChanged(self, message):
+        if self._mFactory is None:
+            # Create the zmq socket in the thread that it will be used, just to be safe.
+            self._mFactory = mf.getZmqPubSubStreamer(self._port)
+        self._mFactory.send_message_topic("lidar_map", messages.ProtoMessage(message=message.SerializeToString()))