This is a bug not present in 5.2.1, discovered upon updating to 5.3.2.

We have a QUdpSocket on the QCoreApplication main thread, that we optionally move to a separate QThread before that thread is started. Once that separate QThread is started, all signals and slots in that thread seem to work except that the QUdpSocket that was moved to it stops emitting readyRead. If I manually call my slot that pulls datagrams from the socket it does have pending datagrams and I am able to read them.

When the QUdpSocket is returned to the main thread it emits readyRead again.

Our temporary fix for this is to close the socket and then immediately bind it again. This is done after the QThread is started.