I'm going to merge #5063 next time I have a few minutes when I'm more awake, which will mean my yak stack[1] is empty and I can go back to working on abortConnection(). As explained in http://twistedmatrix.com/trac/ticket/78, abortConnection() is like loseConnection(), except it doesn't wait until buffers are written out, it closes the connection immediately. The question is, how immediately? My current implementation, a bit like one of the half-close code paths, ends up calling connectionLost directly. That means you can have a call stack that looks like this: MyProtocol.dataReceived TCPConnection.abortConnection ... MyProtocol.connectionLost This can lead to re-entrancy bugs. I am tempted to suggest a policy of No Reactor Reentrancy, but that is currently violated by one of the TCP half-close code paths, and producers if I'm not mistaken. Some options: (a) Leave abortConnection() reentrant. (b) Make abortConnection() non-reentrant, don't change any current APIs. (c) Make all reactor APIs non-reentrant. (Since there's a ticket for documenting the reentrancy policy, you will notice I've added another yak to my stack. I'll finish #78 someday!) Thoughts? References: [1] https://secure.wikimedia.org/wiktionary/en/wiki/yak_shaving