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List:       kde-core-devel
Subject:    Re: Deamons with Qt?
From:       Matthias Ettrich <ettrich () trolltech ! com>
Date:       2001-02-25 12:47:41
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On Sunday 25 February 2001 13:23, Mirko Boehm wrote:
> Richard Moore wrote:
> > Mirko Boehm wrote:
> >> Hi guys,
> >>
> >> does anyone know if there are any reference projects using Qt inside of
> >> deamon programs? I would like to communicate with QSockets and
> >> QDataStreams between a regular KDE program and a process running on a
> >> server without GUI.
> >>
> >> Any ideas?
> >
> > Look at kded etc. IIRC basically you use the GUIenabled argument
> > to QApplication and avoid anything that relies on an event loop
> > existing eg. I'd say QSocket probably won't work as there is
> > no event loop to trigger the QSocketNotifiers, but you should
> > be ok with using QDataStreams and your own select() call.
>
> That is exactly the problem I had, I have already checked out kded and
> dcopserver.
> You either need to have a X Server running to have an event loop, or you
> may have a QApplication, but only that parts of Qt work that do not rely
> on the event loop.
> This limits Qt's fitness for deamons, since it would be a great deal to
> be able to use the sam eIO device classes (for example) your client
> programs use.
>


A deamon needs an event loop anway. Instead of calling select() manually, you 
can just as well use QSocketNotifier and QApplication::exec(). 

Code-wise and performance-wise this makes not difference at all.

The Qt event loop works fine without an X Server, it will then do timers and 
socket notification. In other words: I cannot see the limitation you mention 
at all.

Mathias

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