Is it possible to set a timeout on a socket in Twisted?

Question

I realize I'm probably just dumb and missing something big and important, but I can't figure out how to specify a timeout in twisted using reactor.listenUDP. My goal is to be able to specify a timeout, and after said amount of time, if DatagramProtocol.datagramReceived has not been executed, have it execute a callback or something that I can use to call reactor.stop(). Any help or advice is appreciated. Thanks

Answer 1

Since Twisted is event driven, you don't need a timeout per se. You simply need to set a state variable (like datagramRecieved) when you receive a datagram and register a looping call that checks the state variable, stops the reactor if appropriate then clears state variable:

from twisted.internet import task
from twisted.internet import reactor

datagramRecieved = False
timeout = 1.0 # One second

# UDP code here

def testTimeout():
    global datagramRecieved
    if not datagramRecieved:
        reactor.stop()
    datagramRecieved = False


l = task.LoopingCall(testTimeout)
l.start(timeout) # call every second

# l.stop() will stop the looping calls
reactor.run()

Answer 2

I think reactor.callLater would work better than LoopingCall. Something like this:

class Protocol(DatagramProtocol):
    def __init__(self, timeout):
        self.timeout = timeout

    def datagramReceived(self, datagram):
        self.timeout.cancel()
        # ...

timeout = reactor.callLater(5, timedOut)
reactor.listenUDP(Protocol(timeout))

Answer 3

with reactor we must use callLater. Start timeout countdown when connectionMade. Reset timeout countdown when lineReceived.

Here's the

# -*- coding: utf-8 -*-

from twisted.internet.protocol import Factory
from twisted.protocols.basic import LineReceiver
from twisted.internet import reactor, defer

_timeout = 27


class ServiceProtocol(LineReceiver):

    def __init__(self, users):
        self.users = users


    def connectionLost(self, reason):
        if self.users.has_key(self.name):
            del self.users[self.name]

    def timeOut(self):
        if self.users.has_key(self.name):
            del self.users[self.name]
        self.sendLine("\nOUT: 9 - Disconnected, reason: %s" % 'Connection Timed out')
        print "%s - Client disconnected: %s. Reason: %s" % (datetime.now(), self.client_ip, 'Connection Timed out' )
        self.transport.loseConnection()

    def connectionMade(self):
        self.timeout = reactor.callLater(_timeout, self.timeOut)

        self.sendLine("\nOUT: 7 - Welcome to CAED")

    def lineReceived(self, line):
        # a simple timeout procrastination
        self.timeout.reset(_timeout)

class ServFactory(Factory):

    def __init__(self):
        self.users = {} # maps user names to Chat instances

    def buildProtocol(self, addr):
        return ServiceProtocol(self.users)

port = 8123
reactor.listenTCP(port, ServFactory())
print "Started service at port %d\n" % port
reactor.run()

Answer 4

A better way to do this is with twisted.protocols.policies.TimeoutMixin. It's essentially doing a callLater but abstracted into a Mixin.