echo.py

from twisted.internet import endpoints, defer, protocol, task


class Echo(protocol.Protocol):
    def dataReceived(self, data):
        self.transport.write(data)


@task.react
def main(reactor):
    listening = endpoints.TCP4ServerEndpoint(
        reactor, 9999).listen(protocol.Factory.forProtocol(Echo))

    @listening.addCallback
    def forever(_):
        return defer.Deferred()
    return listening

from twisted.internet import endpoints, defer, protocol, task


class Echo(protocol.Protocol):
    def dataReceived(self, data):
        self.transport.write(data)


@task.react
def main(reactor):
    listening = endpoints.TCP4ServerEndpoint(
        reactor, 9999).listen(protocol.Factory.forProtocol(Echo))

    listen = [False]

    def cycleListening(port):
        if listen[0]:
            print("startListening")
            port.startListening()
            listen[0] = False
        else:
            print("stopListening")
            port.stopListening()
            listen[0] = True

    @listening.addCallback
    def forever(port):
        task.LoopingCall(cycleListening, port).start(30)
        return defer.Deferred()
    return listening