[Interest] QWebSocketServer - server randomly stops acceptingconnections

Jakub Narolewski izowiuz at gmail.com
Thu Apr 4 18:59:29 CEST 2019

I just found this old report:


which sounds suspiciously similar to what I am observing. Hmm, I wonder if you hit the jackpot writing earlier to use QTcpServer to initialize connections.
If I could still use SSL with QWebSocketServer::handleConnection(QTcpSocket *socket) then this could be the solution :]

Will test it and report back!

From: Jason H
Sent: 04 April 2019 17:49
To: Narolewski Jakub
Cc: interest at qt-project.org
Subject: Re: [Interest] QWebSocketServer - server randomly stops acceptingconnections

1. Add a slowloris attack to your fuzzer. Really.
2. "rejected" means something specific. The server does not reject your connection. Your client sends the RST packet.
The "long periods" could just be those first few [hundred] connections where everything goes right, but the slow connection breaks it. I've actually seen this before in company proprietaty code. I wrote a local storage service - previously the storage server was remote - and the timing of packets broke the header parsing. This seems really similar in nature. It -no joke- expected that all the header data in the first packet and no additional data. However now that the service was lusing the localhost (loopback) interface it was no longer subject to MTU and nagle's algorythm.

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