def whenConnected(self, failAfterFailures=None):
        """
        Retrieve the currently-connected L{Protocol}, or the next one to
        connect.

        @param failAfterFailures: number of connection failures after which
            the Deferred will deliver a Failure (None means the Deferred will
            only fail if/when the service is stopped).  Set this to 1 to make
            the very first connection failure signal an error.  Use 2 to
            allow one failure but signal an error if the subsequent retry
            then fails.
        @type failAfterFailures: L{int} or None

        @return: a Deferred that fires with a protocol produced by the
            factory passed to C{__init__}
        @rtype: L{Deferred} that may:

            - fire with L{IProtocol}

            - fail with L{CancelledError} when the service is stopped

            - fail with e.g.
              L{DNSLookupError<twisted.internet.error.DNSLookupError>} or
              L{ConnectionRefusedError<twisted.internet.error.ConnectionRefusedError>}
              when the number of consecutive failed connection attempts
              equals the value of "failAfterFailures"
        """

        Retrieve the currently-connected L{Protocol}, or the next one to
        connect.

        @param failAfterFailures: number of connection failures after which
            the Deferred will deliver a Failure (None means the Deferred will
            only fail if/when the service is stopped).  Set this to 1 to make
            the very first connection failure signal an error.  Use 2 to
            allow one failure but signal an error if the subsequent retry
            then fails.
        @type failAfterFailures: L{int} or None

        @return: a Deferred that fires with a protocol produced by the
            factory passed to C{__init__}
        @rtype: L{Deferred} that may:

            - fire with L{IProtocol}

            - fail with L{CancelledError} when the service is stopped

            - fail with e.g.
              L{DNSLookupError<twisted.internet.error.DNSLookupError>} or
              L{ConnectionRefusedError<twisted.internet.error.ConnectionRefusedError>}
              when the number of consecutive failed connection attempts
              equals the value of "failAfterFailures"
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/internet.py