Running a function periodically in twisted protocol

Question

I am looking for a way to periodically send some data over all clients connected to a TCP port. I am looking at twisted python and I am aware of reactor.callLater. But how do I use it to send some data to all connected clients periodically ? The data sending logic is in Protocol class and it is instantiated by the reactor as needed. I don't know how to tie it from reactor to all protocol instances...

Answer 1

I'd imagine the easiest way to do that is to manage a list of clients in the protocol with connectionMade and connectionLost in the client and then use a LoopingCall to ask each client to send data.

That feels a little invasive, but I don't think you'd want to do it without the protocol having some control over the transmission/reception. Of course, I'd have to see your code to really know how it'd fit in well. Got a github link? :)

Answer 2

You would probably want to do this in the Factory for the connections. The Factory is not automatically notified of every time a connection is made and lost, so you can notify it from the Protocol.

Here is a complete example of how to use twisted.internet.task.LoopingCall in conjunction with a customised basic Factory and Protocol to announce that '10 seconds has passed' to every connection every 10 seconds.

from twisted.internet import reactor, protocol, task

class MyProtocol(protocol.Protocol):
    def connectionMade(self):
        self.factory.clientConnectionMade(self)
    def connectionLost(self, reason):
        self.factory.clientConnectionLost(self)

class MyFactory(protocol.Factory):
    protocol = MyProtocol
    def __init__(self):
        self.clients = []
        self.lc = task.LoopingCall(self.announce)
        self.lc.start(10)

    def announce(self):
        for client in self.clients:
            client.transport.write("10 seconds has passed\n")

    def clientConnectionMade(self, client):
        self.clients.append(client)

    def clientConnectionLost(self, client):
        self.clients.remove(client)

myfactory = MyFactory()
reactor.listenTCP(9000, myfactory)
reactor.run()