I am trying to debug a scenario wherein a program has an http channel/transport that receives an HTTP response; and in some cases (5 out of 10,000) the channel/transport invokes the lost connection callback while the amount of data received is less than the content length.  The connection is used as a producer to write to another connection. I am trying to debug to check whether: (1) the last chunk (20K+) of data sitting in the incoming response is not being propagated up, e.g. due to a prior pauseProducing() call, or (2) the data was not sent from the peer (e.g. connection closed without using so_linger) In general, I "presume" lost connection callback on a producer socket would not be called if there is pending (paused) data that has yet to be written a consumer (socket).  I am also assuming that the assert in internet/abstract.py::resumeProducing() [self.connected and not self.disconnecting] is valid.  I.E: If someone can confirm that scenario (1) above is not possible in twisted (unless a bug). By the time the lost connection callback is called, the transport channel is gone.  I would have to instrument either tcp.py, basic.py, or abstract.py to track this. Any clues/suggestions welcome. Thanks. -Arun