twisted_udp_forwarder.py

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor


forwardMap = { 
    5500  : [ "192.168.110.32:5500", "10.0.1.1:5500" ],
    5499  : [ "192.168.110.32:5499" ],
    15501 : [ "localhost:5501" ]
    }


class Forward(DatagramProtocol):
    def __init__(self, targetTuples):
        self._targetTuples = targetTuples
        
    def datagramReceived(self, data, hostAndPort):
        for targetHost, targetPort in self._targetTuples:
            #print "forwarding %r from %s:%d to %s:%d" % (data, host, port, targetHost, targetPort)
            self.transport.write(data, (targetHost, targetPort))
            
def bindListeners(resolvedMap):
    for port, targetPairs in resolvedMap.items():
        reactor.listenUDP(port, Forward(targetPairs))

def resolved(ip, lport, host, dport, rmap={}):
    rmap.setdefault(lport, []).append((ip, dport))
    cons = lambda a, b: a + b
    if (len(reduce(cons, forwardMap.values())) == len(reduce(cons, rmap.values()))):
        bindListeners(rmap)
            
for port, destinations in forwardMap.items():
    strPairs = [d.split(':') for d in destinations]
    map(lambda hostAndPort: (reactor.resolve(hostAndPort[0]).addCallback(resolved, port, hostAndPort[0], int(hostAndPort[1]))), strPairs)

reactor.run()

Useful, indeed!