@ character meaning in multicast addresses

[jhr]

I trouble-shooted an old signage installation, where they replaced rack-mount media server (apparently some kind of hotel-TV server or similar) with new one. The old server provided unicast http-streams but the new one has multicast udp-streaming. I thought that would be just simple URL change but no, it didn't work. After some google searches I noticed that all examples had multi-cast addresses starting with mysterious @ character and after adding that the stream started to work.

I suppose this is specific to VLC since no other multicast documentation mention anything about @? What does it mean, is it just some legacy thing from history or does it have an actual purpose?

[Rémi Denis-Courmont]

@ separates the source and destination/group addresses.