QWebSocket uses QueuedConnection to handle readyRead() signals (see qwebsocket_p.cpp in makeConnections()) from the backing QTcp/SslSocket, but it uses direct connection from the socket to notify of disconnection.

https://code.qt.io/cgit/qt/qtwebsockets.git/tree/src/websockets/qwebsocket_p.cpp#n624

That can lead to situation where disconnected() signal is fired first and then the message is reported after that, which complicates the application logic a bit because this would have to be taken into account.