Use PAIR socket for slam, tidy up python stuff.

SlamController/slam_servicer.py

@@ -3,19 +3,21 @@ import slam_streamer as slam
 from threading import Thread
 
 class SlamServicer(SlamController_pb2_grpc.SlamControlServicer):
+    slam_thread = None
+    
     def __init__(self, lidar_connection):
         print('Servicer initialised')
         self.slam = slam.SlamStreamer(lidar_connection=lidar_connection)
 
     def start_map_streaming(self, request, context):
-        if not hasattr(self, 'slamThread'):
+        if self.slam_thread is None:
             # Don't bother creating and starting slam more than once.
             self.slam.port = request.port
             self.slam.map_pixels = request.map_size_pixels
             self.slam.map_meters = request.map_size_meters
-            slamThread = Thread(target=self.slam.start)
-            slamThread.start()
+            self.slam_thread = Thread(target=self.slam.start)
+            self.slam_thread.start()
 
     def stop_streaming(self, request, context):
-        if hasattr(self, 'slamThread'):
+        if self.slam_thread is not None:
             self.slam.stop_scanning()

SlamController/slam_streamer.py

@@ -31,6 +31,10 @@ class SlamStreamer:
         to calling this method, and changing those values after
         calling this method will have no effect.
         '''
+        
+        # Block until user opens zmq.
+        self._socket.recv()
+
         # Adapted from BreezySLAM rpslam example.
         # Connect to Lidar unit
         lidar = Lidar(self._lidar_connection)
@@ -77,7 +81,7 @@ class SlamStreamer:
         return zmq.Context.instance()
 
     def _create_tcp_pub_socket(self):
-        return self._create_context().socket(zmq.PUB)
+        return self._create_context().socket(zmq.PAIR)
 
     def _start_socket(self, socket, port):
         socket.bind('tcp://*:' + str(self._port))