For errors such as "host not found" or "connection refused" the QWebSocket::errorString() method returns the string "Unknown Error" event when the error() method returns the correct error code.

I've attached a quick test, that attempts to connect to ws://localhost:4343 and prints the errorString on state change.

The issue seems to be caused by the Ctor for QWebSocketPrivate that sets the value for m_errorString to QWebSocket::tr("Unknown error"), this in turn causes QWebSocketPrivate::errorString() to always fail a check against m_errorString.isEmpty(), and always returning "Unknown Error".

Attached is also a patch that leaves the default value for m_errorString as empty and sets it in errorString() instead.