def service(description, factory, reactor=None):
    """
    Return the service corresponding to a description.

    @param description: The description of the listening port, in the syntax
        described by L{twisted.internet.endpoints.serverFromString}.
    @type description: C{str}

    @param factory: The protocol factory which will build protocols for
        connections to this service.
    @type factory: L{twisted.internet.interfaces.IProtocolFactory}

    @rtype: C{twisted.application.service.IService}
    @return: the service corresponding to a description of a reliable stream
        server.

    @see: L{twisted.internet.endpoints.serverFromString}
    """
    if reactor is None:
        from twisted.internet import reactor

    svc = StreamServerEndpointService(
        endpoints.serverFromString(reactor, description), factory)
    svc._raiseSynchronously = True
    return svc

    Return the service corresponding to a description.

    @param description: The description of the listening port, in the syntax
        described by L{twisted.internet.endpoints.serverFromString}.
    @type description: C{str}

    @param factory: The protocol factory which will build protocols for
        connections to this service.
    @type factory: L{twisted.internet.interfaces.IProtocolFactory}

    @rtype: C{twisted.application.service.IService}
    @return: the service corresponding to a description of a reliable stream
        server.

    @see: L{twisted.internet.endpoints.serverFromString}
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/strports.py