I am new to this list, and could not find a way to search the archives, so please forgive me and/or point me to a past thread if I am re-hashing old news. I've set up calendar server (employing advice from Tony Rush's blog) and things worked great for a few months. Then at the end of April, it stopped.  I haven't dealt with this because our first child joined us in early April, and some priorities have shifted... The only thing that may have changed is, perhaps, an update to Leopard from Apple.  After the recent update to 10.5.3, there was no sudden re-enabling of the Calendar Server, for which I had illogically hoped. It appears that twisted is looking to listen to an address that is already in use. Any advice is much appreciated. Here's what I have from my error log produced upon the failure to start: Removing stale pidfile /Library/CalendarServer/logs/caldavd.pid 2008-06-02 04:57:04-0500 [-] Log opened. 2008-06-02 04:57:04-0500 [-] twistd 2.5.0+rUnknown (/System/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python 2.5.1) starting up 2008-06-02 04:57:04-0500 [-] reactor class: <class 'twisted.internet.selectreactor.SelectReactor'> 2008-06-02 04:57:04-0500 [-] 1 processors found, configuring 1 processes. 2008-06-02 04:57:04-0500 [-] twistedcaldav.logging.AMPLoggingFactory starting on "'logs/caldavd.sock'" 2008-06-02 04:57:04-0500 [-] Traceback (most recent call last): 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/bin/twistd", line 21, in <module> 2008-06-02 04:57:04-0500 [-]     run() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/scripts/twistd.py", line 27, in run 2008-06-02 04:57:04-0500 [-]     app.run(runApp, ServerOptions) 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/app.py", line 379, in run 2008-06-02 04:57:04-0500 [-]     runApp(config) 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/scripts/twistd.py", line 23, in runApp 2008-06-02 04:57:04-0500 [-]     _SomeApplicationRunner(config).run() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/app.py", line 158, in run 2008-06-02 04:57:04-0500 [-]     self.postApplication() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/scripts/_twistd_unix.py", line 213, in postApplication 2008-06-02 04:57:04-0500 [-]     startApplication(self.config, self.application) 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/scripts/_twistd_unix.py", line 174, in startApplication 2008-06-02 04:57:04-0500 [-]     service.IService(application).privilegedStartService() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/service.py", line 228, in privilegedStartService 2008-06-02 04:57:04-0500 [-]     service.privilegedStartService() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/service.py", line 228, in privilegedStartService 2008-06-02 04:57:04-0500 [-]     service.privilegedStartService() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/internet.py", line 68, in privilegedStartService 2008-06-02 04:57:04-0500 [-]     self._port = self._getPort() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/application/internet.py", line 86, in _getPort 2008-06-02 04:57:04-0500 [-]     return getattr(reactor, 'listen'+self.method)(*self.args, **self.kwargs) 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/internet/posixbase.py", line 432, in listenUNIX 2008-06-02 04:57:04-0500 [-]     p.startListening() 2008-06-02 04:57:04-0500 [-]   File "/Library/Twisted/twisted/internet/unix.py", line 89, in startListening 2008-06-02 04:57:04-0500 [-]     raise CannotListenError, (None, self.port, le) 2008-06-02 04:57:04-0500 [-] twisted.internet.error.CannotListenError: Couldn't listen on any:logs/caldavd.sock: (48, 'Address already in use'). -- Conrad Wasmer