I just saw that a QNetworkReply::TimeoutError code exists. Shouldn't this code be set when a timeout occurred ? Is this a bug or did I misunderstand something ?

Thank you Christian! https://bugreports.qt.io/browse/QTBUG-88063 describes exactly what I've been seeing.

@JonB Thank you!

Process still block, when I lost connection.

@mistralegna AFAIK, You can set bool QAbstractSocket::isValid() const on the given address provided. you can also get error signal from the websocket, if it is not valid address. void QAbstractSocket::error(QAbstractSocket::SocketError socketError). check here . But , the isvlaid() is not very efficient like in your case WS:// instead of WSS://. Because to my knowledge isValid() says true to any address , if it is inform of address/standard way of address. In your cases, I prefer to use Regular Expression before connection to socket.

mysql_options called with MYSQL_OPT_CONNECT_TIMEOUT returns 0 (success) both for mysql and mariadb libraries.