Thanks very much! This seems to be working for Age of Empires 1 & 2 — at the very least, it resolves the issues with getting into the game lobby, and (in Age of Empires 2) starting a LAN game. Promising-looking packets are flowing. I haven't got a second copy of the game here to test an actual LAN multiplayer game fully at the moment, but this is definitely an improvement.
Indeed, this works better than the [patch here](https://github.com/ValveSoftware/Proton/issues/3189#issuecomment-1823909045) did when I tested it, though that may be due to other wine or game updates since: the lobby no longer disconnects on AOE2.
One minor thought about the implementation: does it need to support other broadcast addresses, not just 255.255.255.255? It's fine as-is for Age of Empires, but maybe something else cares.