Comment 37 for bug 1689087

uTorrent is using UPNP (automatic port forwardings), which is not enabled in all routers. So it is not enough when we want something that always works.
The pointer with the data protection act is a good one. When we start collecting statistics we should look into legal issues before we implement something. But I guess (not know!) that for the relay server as such it doesn't matters.

From looking at their sources, it seems that Wesnoth is using a single metaserver/relay instance for all games. So they have one process with only one open port for it.
I can't say whether a single relay server is possible for Widelands, too. Until we have it and try it out, I don't think we can say much about how busy the relay is with one game and how many games it might be able to manage. But it should be possible to design the protocol and the relay in a way that it can easily be upgraded to support multiple games at once, if we want to try this path. Of course, that would mean that a crash of the (single) relay process breaks all currently running games.