udp_client.py

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

class EchoClientDatagramProtocol(DatagramProtocol):

    def startProtocol(self):
        self.transport.connect('127.0.0.1', 8000)
        self.sendDatagram()
    
    def sendDatagram(self):
        self.transport.write('hello')

    def datagramReceived(self, datagram, host):
        print 'Datagram received: ', repr(datagram)
        self.sendDatagram()

def main():
    protocol = EchoClientDatagramProtocol()
    t = reactor.listenUDP(0, protocol)
    reactor.run()

if __name__ == '__main__':
    main()