[Twisted-Python] Help: how to run something at shutdown time

I'm running an xmlrpc server using twisted xmlrpc. I use reactor.callWhenRunning() to do some setup when the server is started, but I need to also do some special shutdown steps when the server is stopped. I don't see any callWhenStopped() or something to that effect...so is there a way to call specific methods when shutdown happens? Any help is appreciated, -David -- Presenting: mediocre nebula.