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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have been trying to track down a random websocket disconnection issue that we are facing.<o:p></o:p></p>
<p class="MsoNormal">In our application, after some random number of hours of a good websocket connection that is
<o:p></o:p></p>
<p class="MsoNormal">transferring data back and forth, the connection suddenly breaks. We are using noPoll only<o:p></o:p></p>
<p class="MsoNormal">for the client side of a WebSocket connection. The server side is Apache frontend with
<o:p></o:p></p>
<p class="MsoNormal">node app backend.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">After eliminating all other probable causes, I enabled noPoll debug logs and was finally able
<o:p></o:p></p>
<p class="MsoNormal">to catch the error which causes a disconnect: <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">nopoll_conn.c:2797 Failed to get next 2 bytes to read header from the wire, failed to received content, shutting down id=2 the connection
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Reproducing this is difficult since it takes anything from a couple of hours to a couple of days<o:p></o:p></p>
<p class="MsoNormal">but eventually it happens. My debugging efforts at narrowing this down is thus taking quite a while.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We are using secure web sockets (wss://). <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Looking at the code, it seems that in the noPoll library, we expect the next two bytes of
<o:p></o:p></p>
<p class="MsoNormal">the websocket header to be always available if we read the first two bytes.
<o:p></o:p></p>
<p class="MsoNormal">I think that over TCP (and possibly even more so over TLS)<o:p></o:p></p>
<p class="MsoNormal">this may not always be guaranteed. The socket is non-blocking and it may occasionally<o:p></o:p></p>
<p class="MsoNormal">have a pattern that 4 bytes are split over two (or more) TCP segments.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For reading first two bytes noPoll library seems to be buffering if data is not available.<o:p></o:p></p>
<p class="MsoNormal">For correctness, should not this be done for subsequent parts of the header too?<o:p></o:p></p>
<p class="MsoNormal">Of course, I am not an expert here so could you analyze and let me know what is could<o:p></o:p></p>
<p class="MsoNormal">be the root cause? What should be my next steps?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have already verified that this is not due to http(s) server error. I did a TCP dump<o:p></o:p></p>
<p class="MsoNormal">and confirmed that when this happens, the first FIN is sent by the client (noPoll) to the http server.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rahul<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rahul Kale<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">IP Video Systems<o:p></o:p></p>
<p class="MsoNormal">Barco, Inc<o:p></o:p></p>
<p class="MsoNormal">1287 Anvilwood Ave<o:p></o:p></p>
<p class="MsoNormal">Sunnyvale, CA 94089<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tel +1 408 400 4238<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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