Yes! UPnP auto-discovery in xbmc now works! Per XBMCFanboy suggestion, I looked at the XBMS protocol (for auto-discovery) and realized they were using the 255.255.255.255 address to broadcast their search. I tried with Platinum and it worked! When I send a M-SEARCH request on this address & the UPnP port 1900, EVERY UPnP media servers respond to me! That means you can have more than 1 UPnP server on a host or many hosts and they will all be detected. This is very cool.

Now there’s still a pb I have to work on, since the xbox cannot receive multicast packets, it’s not able to receive the notifications when UPnP servers go away. Although it’s pretty rare, it is possible and the device would still be in the list in xbmc. Kind of a cosmetic detail but I am a complete freak when it comes to the last 5% that makes a good product a perfect one.