Where does the error "QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread" come from if I don't have sockets?

Question

Qt

The application writes QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread.
All mentions of this error in Google and SO are connected with work with sockets. But I don't have sockets in my application (or I can't find them).
Where might this message come from?
Is it possible somehow under debugging, catching this message, to go to the source of the message?
I work with QSerialPort, there are streams, QML

Answer 1

Some part of the application that uses libraries that use sockets internally runs on a separate thread.