Thanks for your explanation. It helps me a lot. I've still one more question  : what if Service3 want to compute the mean between Service1 and Service2. It means that the Client will not care if it uses Service 1,2 or 3 but that Service 3 itself want to specifically ask Service1 and 2, even if they have lower priority ! (and of course, it doesn't want to ask himself). Is it possible with the FLAG ? Thanks a lot for your help. Lionel <div class="gmail_quote">On Tue, Dec 2, 2008 at 3:34 PM, Kalle Vahlman <<a href="mailto:kalle.vahlman@gmail.com">kalle.vahlman@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">2008/12/2 Lionel Dricot <<a href="mailto:zeploum@gmail.com">zeploum@gmail.com</a>>: <div class="Ih2E3d">> Hello, > > I want to use D-Bus to allow one "client" to get some information from a > "service" object. But this service object could be implemented multiple > times. I want to be able to just launch a new implementation of "service" in > the pool without having to change the "client" implementation at all. Client > should automatically use the the service with the highest priority. </div>[snip] <div class="Ih2E3d">> So, how would you do that ? </div>When D-Bus services register bus names they can determine with flags how they react when someone else owns the name or tries to register the same name. Also you get signals (NameOwnerChanged and NameLost) from the Bus when such activity occurs. So in your example, the local service (high priority) should request the service name with the flag (names from the low-level lib) DBUS_NAME_FLAG_REPLACE_EXISTING so it replaces any other service using the name. The website service then requests the same bus name with DBUS_NAME_FLAG_ALLOW_REPLACEMENT so that the higher priority service can always snatch it when it comes around again. If you need more featureful priority handling than high/low, you'll need to implement some sort of negotiation between the service instances, but the client side still doesn't need to know about it. More details about requesting names: <a href="http://dbus.freedesktop.org/doc/dbus/api/html/group__DBusBus.html#g4b4903adad0199119c9e49ad18e0cb25" target="_blank">http://dbus.freedesktop.org/doc/dbus/api/html/group__DBusBus.html#g4b4903adad0199119c9e49ad18e0cb25</a> -- Kalle Vahlman, <a href="mailto:zuh@iki.fi">zuh@iki.fi</a> Powered by <a href="http://movial.fi" target="_blank">http://movial.fi</a> Interesting stuff at <a href="http://sandbox.movial.com" target="_blank">http://sandbox.movial.com</a> See also <a href="http://syslog.movial.fi" target="_blank">http://syslog.movial.fi</a> </blockquote></div>