python - asyncore.loop doesn't terminate when there are no more connections

Question

I am following some example code to use asyncore here, only having set a timeout value for asyncore.loop as in the following full example:

import smtpd
import asyncore

class CustomSMTPServer(smtpd.SMTPServer):

    def process_message(self, peer, mailfrom, rcpttos, data):
        print 'Receiving message from:', peer
        print 'Message addressed from:', mailfrom
        print 'Message addressed to  :', rcpttos
        print 'Message length        :', len(data)
        return

server = CustomSMTPServer(('127.0.0.1', 1025), None)

asyncore.loop(timeout = 1)

I have expected that a timeout occurs after 1 second, but this is not the case. The code runs much longer for than one second. What am I missing here?

Answer 1

The timeout argument to asyncore.loop() is the amount of time the select.select call will wait for data. If there is no data before the timeout runs out it will loop and call select.select again.

Same for the channels idea. This does not mean open sockets but means active asyncore.dispatcher or asynchat.async_chat instances. If you want to stop the loop you will have to call the close() method on ALL instances registered.

In your case server.close() will close the instance/channel and remove it from the asyncore loop. If no more channels are active this loop will then terminate itself.