These are three questions:

1.) can you use POSIX functions inside Qt? Anser is yes, its C/C++ and you can do anything that C/C++ allows.

2.) Can you use possix threads? Theoretically yes. But, and that is the important thing, you can’t use signal/slot across threads without using QtThreads and Qt message loops.

3.) What do you want to do with POSIX message queues? Inter process communication? Then see answer 1 :-)

2.) Can you use possix threads? Theoretically yes. But, and that is the important thing, you can’t use signal/slot across threads without using QtThreads and Qt message loops.

This is slightly incorrect — you can mix QThread and native threads, and even use signals from native threads.

You can emit Signals from natic threads, but can’t use slots inside them :-)
But I think,. on Linux, QThread objects just encapsulate POSIX threads, don’t they?

But for cross thread signal/slot you need QThreads (at least for the receiving thread) and there a QMessageLoop.

Take a look at the QtService solution [qt.gitorious.org]. I have used this successfully in the past.

I would just use QThread for conveniemce since it just wraps POSIX threads.

Just a note: Local sockets would be more portable than POSIX message queues. Also it scales better if you intend to distribute among more machines later. (see: http://doc.qt.nokia.com/4.7-snapshot/qlocalsocket.html

[EDIT: fixed link, Volker]