Run ./errortest.py, then run another ./errortest.py while the first one is still running. The second one *should* exit with an error, but instead it gets stuck in the event loop.

errortest.py

#!/usr/bin/env python
import sys

# This is just for me. Comment this out if you want.
sys.path.insert(0, 'Twisted-12.2.0')
sys.path.insert(0, 'zope.interface-4.0.1')

import logging
from twisted.internet import reactor, protocol
from twisted.internet.endpoints import TCP4ServerEndpoint

def errorHandler(failure):
    logger = logging.getLogger('tunnel_server')
    logger.error("CRITICAL ERROR IN SERVER: %s" % failure.getErrorMessage())
    logger.error(failure.getTraceback(0, 'verbose'))
    print '!!!!!!!!!! Stopping server!'
    sys.exit(1)

class Kernel(protocol.Factory):
    pass

if __name__ == "__main__":
    logger = logging.getLogger('tunnel_server')
    hdlr = logging.StreamHandler(sys.stdout)
    formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
    hdlr.setFormatter(formatter)
    logger.addHandler(hdlr) 
    logger.setLevel(logging.DEBUG)

    endpoint = TCP4ServerEndpoint(reactor, 1234)
    listener = endpoint.listen(Kernel())
    listener.addErrback(errorHandler)

    logger.info("All ready, entering reactor main loop")
    reactor.run()

gistfile1.txt

# Running errortest.py while another instance is already running
$ python errortest.py 
2013-02-01 22:47:16,046 ERROR CRITICAL ERROR IN SERVER: Couldn't listen on any:1234: [Errno 48] Address already in use.
2013-02-01 22:47:16,046 ERROR *--- Failure #6 (pickled) ---
errortest.py:31: <module>(...)
Twisted-12.2.0/twisted/internet/endpoints.py:271: listen(...)
 [Capture of Locals and Globals disabled (use captureVars=True)]
--- <exception caught here> ---
Twisted-12.2.0/twisted/internet/defer.py:105: execute(...)
Twisted-12.2.0/twisted/internet/posixbase.py:476: listenTCP(...)
Twisted-12.2.0/twisted/internet/tcp.py:969: startListening(...)
 [Capture of Locals and Globals disabled (use captureVars=True)]
twisted.internet.error.CannotListenError: Couldn't listen on any:1234: [Errno 48] Address already in use.
*--- End of Failure #6 ---

!!!!!!!!!! Stopping server!
2013-02-01 22:47:16,046 INFO All ready, entering reactor main loop
(at this point, the process is stuck here even though it should exit with exit code 1)