def _transport_factory(self): "create and return the transport factory" try: factory = WampWebSocketClientFactory( self._component, url=self.wmp_url, serializers=self.wmp_serializers, loop=self._loop) except Exception as exc: raise Exception("could not build transport factory: %s" % exc) else: factory._session_joined = asyncio.Future(loop=self._loop) self._logger.info("WAMP connecting to %s, realm '%s'" % (self.wmp_url, self.wmp_realm)) return factory