fix OSError: [Errno 107] Transport endpoint is not connected

cfr. #739
cfr. https://linux.die.net/man/2/shutdown

Author: brubbel

opcua/client/ua_client.py

@@ -137,15 +137,21 @@ def connect_socket(self, host, port):
         """
         self.logger.info("opening connection")
         sock = socket.create_connection((host, port))
-        # nodelay ncessary to avoid packing in one frame, some servers do not like it
+        # nodelay necessary to avoid packing in one frame, some servers do not like it
         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
         self._socket = ua.utils.SocketWrapper(sock)
         self.start()
 
     def disconnect_socket(self):
         self.logger.info("Request to close socket received")
         self._do_stop = True
-        self._socket.socket.shutdown(socket.SHUT_RDWR)
+        try:
+            self._socket.socket.shutdown(socket.SHUT_RDWR)
+        except OSError as exc:
+            if exc.errno == errno.ENOTCONN:
+                pass # Socket is not connected, so can't send FIN packet.
+            else:
+                raise
         self._socket.socket.close()
         self.logger.info("Socket closed, waiting for receiver thread to terminate...")
         if self._thread and self._thread.is_alive():