PATH_PLANNING: check param server for id prior to using input

ap_lib/src/ap_lib/distributed_algorithms.py

@@ -17,7 +17,7 @@ import rospy
 # ACS imports
 import ap_msgs.msg as apmsg
 import ap_lib.bitmapped_bytes as bytes
-
+import socket
 
 class LossyDataExchange(object):
     ''' Abstract class used in support of reliable information exchange
@@ -55,13 +55,14 @@ class LossyDataExchange(object):
         @param msg_publisher: ROS publisher to the swarm_data_msg topic
         @param lock: reentrant lock that will be used to enforce thread safety
         '''
-        if own_id is None:
+        try:
             if rospy.has_param("aircraft_id"):
                 self._own_id = int(rospy.get_param("aircraft_id"))
-            else:
+        except socket.error:
+            if own_id is not None: 
+                self._own_id = own_id
+            else: 
                 rospy.logerr("cannot retrieve aircraft_id from parameter server")
-        else:
-            self._own_id = own_id
 
         self._short_list_parser = bytes.UShortListParser()
         self._short_list_parser.source_id = self._own_id