I never tried to start a thread with event loop in a program without main event loop (QApplication). My guess: it will work inside your thread, but you will not be able to communicate with the thread from main thread using signals/slots.
Ok guy thank you for that much replies :P! I solved the issue by myself anyway. In case sombebody has a similar problem here comes the solution:
What I did wrong was that I connected a time consuming function to the UpdateClient::tcpReady() slot. In this function I did some stuff which also lead to the emission of UpdateClient::tcpReady(). This broke the QEventQueue. So to what I had to chance was to skip the direct signal slot connection an do this in the UpdateClient::tcpReady():
Thank you for you help.
Probably the thing is, QSerialPort has a problem to work in a new thread.
I can handle the other QObject in a new thread very well, and the exception only happens when the Object contains QSerialPort.
Also, in my last post, I actually never user QList, although Qt tells me something wrong with QList.
I have given up on working serialThread. QSerialPort does work good in the main thread.