def _ebServiceUnknown(self, failure):
        """
        Connect to the default port when the service name is unknown.

        If no SRV records were found, the service name will be passed as the
        port. If resolving the name fails with
        L{error.ServiceNameUnknownError}, a final attempt is done using the
        default port.
        """
        failure.trap(error.ServiceNameUnknownError)
        self.servers = [dns.Record_SRV(0, 0, self._defaultPort, self.domain)]
        self.orderedServers = []
        self.connect()

        Connect to the default port when the service name is unknown.

        If no SRV records were found, the service name will be passed as the
        port. If resolving the name fails with
        L{error.ServiceNameUnknownError}, a final attempt is done using the
        default port.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/srvconnect.py