Not a game dev but I guess you could go quite far with just an IRC server. Crosshatch your world in chat rooms, with a bot in each one. A player sends a comman

Not a game dev but I guess you could go quite far with just an IRC server. Crosshatch your world in chat rooms, with a bot in each one. A player sends a command to his current chat room; the bot validates the player position and current action. Other players listen to bot responses in all nine chatrooms around them.