The current process has used all of its system allowance of handles for Window Manager objects.

[koahnig]

Anyone able to give me a clue what might be wrong with my application?

WdCheck: Reinit TCP socket for TcpExtFrameServer 
QEventDispatcherWin32::registerTimer: Failed to create a timer (The current process has used all of its system allowance of handles for Window Manager objects.)
CreateWindow() for QEventDispatcherWin32 internal window failed (The current process has used all of its system allowance of handles for Window Manager objects.)
Qt: INTERNAL ERROR: failed to install GetMessage hook: 1158, The current process has used all of its system allowance of handles for Window Manager objects.

It run on windows 64 bit.
Is there an upper limit for timers?
Or is the eventloop filled with timer events?

[koahnig]

OK, it was a bit premature to ask immediately.

I found this post https://forum.qt.io/topic/54438/solved-qt-5-4-1-qtimer-using-up-all-handles-for-window-manager-objects

Actually with QNetworkAccessManager I was a bit sloppy. Need to check if it helps already.

Edit[koahnig]: It helped. Therefore, pay attention when generating new QNetworkAccessManger objects.