The method in

void QtServiceSysPrivate::incomingConnection(int socketDescriptor);

is an reimplemented method from QTcpServer. But in Qt5 the actual signature changed to

void QTcpServer::incomingConnection(qintptr socketDescriptor);

This is incompatible for the compiler and so the reimplemented version is never called! The
communication between instances over sendCMD() does not work.

Can you fix this please to use qintptr instead of int? I tried it. After that everything works like under Qt4. Maybe you need a pre-processor switch for Qt4 and Qt5 argument types.

Thanks
Andreas