def connectedServerAndClient(ServerClass, ClientClass,
                             clientTransportFactory=makeFakeClient,
                             serverTransportFactory=makeFakeServer,
                             debug=False, greet=True):
    """
    Connect a given server and client class to each other.

    @param ServerClass: a callable that produces the server-side protocol.
    @type ServerClass: 0-argument callable returning L{IProtocol} provider.

    @param ClientClass: like C{ServerClass} but for the other side of the
        connection.
    @type ClientClass: 0-argument callable returning L{IProtocol} provider.

    @param clientTransportFactory: a callable that produces the transport which
        will be attached to the protocol returned from C{ClientClass}.
    @type clientTransportFactory: callable taking (L{IProtocol}) and returning
        L{FakeTransport}

    @param serverTransportFactory: a callable that produces the transport which
        will be attached to the protocol returned from C{ServerClass}.
    @type serverTransportFactory: callable taking (L{IProtocol}) and returning
        L{FakeTransport}

    @param debug: Should this dump an escaped version of all traffic on this
        connection to stdout for inspection?
    @type debug: L{bool}

    @param greet: Should the L{IOPump} be L{flushed <IOPump.flush>} once before
        returning to put the protocols into their post-handshake or
        post-server-greeting state?
    @type greet: L{bool}

    @return: the client protocol, the server protocol, and an L{IOPump} which,
        when its C{pump} and C{flush} methods are called, will move data
        between the created client and server protocol instances.
    @rtype: 3-L{tuple} of L{IProtocol}, L{IProtocol}, L{IOPump}
    """
    c = ClientClass()
    s = ServerClass()
    cio = clientTransportFactory(c)
    sio = serverTransportFactory(s)
    return c, s, connect(s, sio, c, cio, debug, greet)

    Connect a given server and client class to each other.

    @param ServerClass: a callable that produces the server-side protocol.
    @type ServerClass: 0-argument callable returning L{IProtocol} provider.

    @param ClientClass: like C{ServerClass} but for the other side of the
        connection.
    @type ClientClass: 0-argument callable returning L{IProtocol} provider.

    @param clientTransportFactory: a callable that produces the transport which
        will be attached to the protocol returned from C{ClientClass}.
    @type clientTransportFactory: callable taking (L{IProtocol}) and returning
        L{FakeTransport}

    @param serverTransportFactory: a callable that produces the transport which
        will be attached to the protocol returned from C{ServerClass}.
    @type serverTransportFactory: callable taking (L{IProtocol}) and returning
        L{FakeTransport}

    @param debug: Should this dump an escaped version of all traffic on this
        connection to stdout for inspection?
    @type debug: L{bool}

    @param greet: Should the L{IOPump} be L{flushed <IOPump.flush>} once before
        returning to put the protocols into their post-handshake or
        post-server-greeting state?
    @type greet: L{bool}

    @return: the client protocol, the server protocol, and an L{IOPump} which,
        when its C{pump} and C{flush} methods are called, will move data
        between the created client and server protocol instances.
    @rtype: 3-L{tuple} of L{IProtocol}, L{IProtocol}, L{IOPump}
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/iosim.py