If you do reactor.listenTCP on a factory, startFactory and stopFactory are never called. I therefore suggest that we add methods doStart and doStop to protocol.Factory, like so, and have them called in listenTCP/UDP/SSL, and remove calls to start/stopFactory from app.Appliecation: class Factory: running = 0 def doStart(self): if not self.running: self.running = 1 self.startFactory() def doStop(self): if self.running: self.running = 0 self.stopFactory() This ensures the start/stopFactory methods will only be called once, even if the factory is added to multiple Ports, and makes sure that they get called even if the factory is added to the reactor directly.