Sorry I have not been able to find a better title, please see the attached example which may be more descriptive. Here is what it does: * set up an SSH connection * open a TCP forwarding channel through this connection * do something through the tunnel that will trigger an errback (in the example, try to do an XMLRPC call with no one listening on the tunnel's end) This scenario gives me the following traceback (tested with Twisted 8.1.0 and 8.2.0): -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/python/log.py", line 84, in callWithLogger return callWithContext({"system": lp}, func, *args, **kw) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/python/log.py", line 69, in callWithContext return context.call({ILogContext: newCtx}, func, *args, **kw) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/python/context.py", line 59, in callWithContext return self.currentContext().callWithContext(ctx, func, *args, **kw) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/python/context.py", line 37, in callWithContext return func(*args,**kw) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/internet/selectreactor.py", line 156, in _doReadOrWrite self._disconnectSelectable(selectable, why, method=="doRead") File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/internet/posixbase.py", line 193, in _disconnectSelectable selectable.connectionLost(f) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/internet/tcp.py", line 520, in connectionLost protocol.connectionLost(reason) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/conch/ssh/forwarding.py", line 129, in connectionLost self.channel.loseConnection() File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/conch/ssh/channel.py", line 253, in loseConnection self.conn.sendClose(self) File "/usr/lib/python2.5/site-packages/Twisted-8.2.0-py2.5-linux-i686.egg/twisted/conch/ssh/connection.py", line 491, in sendClose self.channelsToRemoteChannel[channel])) exceptions.KeyError: -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- It works well in the other cases, i.e.: * the errback is triggered but the tunnel is not used (comment line 57, uncomment line 59) * the errback is not triggered (start the XMLRPC server by uncommenting line 100), using the tunnel or not You get the error only when the tunnel is used AND the errback is triggered. To run the example execute it with an user name that can login using ssh on your host, e.g. 'python test.py someuser' and enter its password. Cheers, Luper