在python中，如何让UDPServer自行关闭？

import threading
import time
import SimpleHTTPServer
import SocketServer

PORT = 8000
Handler = SimpleHTTPServer.SimpleHTTPRequestHandler
httpd = SocketServer.TCPServer(("", PORT), Handler)

def worker():

    # minimal web server.  serves files relative to the
    print "serving at port", PORT
    httpd.serve_forever()

def my_service():
    time.sleep(3)
    print "I am going down"
    httpd.shutdown()

h = threading.Thread(name='httpd', target=worker)
t = threading.Thread(name='timer', target=my_service)

h.start()
t.start()

#!/usr/bin/env python

# Copyright (c) 2001-2009 Twisted Matrix Laboratories.
# See LICENSE for details.

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

# Here's a UDP version of the simplest possible protocol
class EchoUDP(DatagramProtocol):
    def datagramReceived(self, datagram, address):
        self.transport.write(datagram, address)

def main():
    reactor.listenUDP(8000, EchoUDP())
    reactor.run()

if __name__ == '__main__':
    main()

self.server

handle

self.server.shutdown()