Thanks.
I couldn't find a bug myself but it seems there is one, so in the event that someone else might be interested it is https://bugreports.qt.io/browse/QTBUG-43837.

OK. Solution was so simple. I am on windows and there is file named hosts on the path C:\Windows\System32\drivers\etc. just edit this file and add this line:

127.0.0.1 localhost

Sometimes some application during the installation edits this file and replaces
127.0.0.1 localhost
with 0.0.0.0 localhost

so you need to fix it manually.

Hi and welcome to devnet,

Currently just had a segmentation fault on OS X, will need to take a deeper look

Then just edit the title by hand and prepend [solved]

I have shown only a simplified version of my code.
Actually I have lots of networking happening serially and parallel.
I transferred all of this to a new thread so as to keep my GUI thread free.
Thanks for your advice!

Hi Arthur,
Very interesting link. Actually some of his other projects look quite interesting too, albeit being in german.