QWebSocketPrivate::QWebSocketPrivate(const QString &origin, QWebSocketProtocol::Version version, QWebSocket *pWebSocket) does not initialize the m_handshakeState field.

This causes the first call to QWebSocket::processHandshake to skip the state switch, and in the final method check to emit the error signal while resetting m_handshakeState to AllDoneState. From there on, things work.