A realtime multiplayer bullshit bingo game with prefilled or custom bingo cards for things like online meetings or apple keynotes.

Demo link is in the readme if you want to try it.

I always wanted to build something realtime-ish for the web that multiple people can use simultaneously. I was wondering how such systems could work and how hard the realtime part would be.

Here I'm using Postges listen/notify to let my rust service know when tables change without having to query these tables all the time. First I was using one listener for every websocket connection. But a listener keeps a postgres connection hostage, so it would cause problems with too many clients holding a WS connection.

Next thing I tried was to have just one listener and send updates to the websocket handler via a mpmc channel. But the channel receivers remove messages from the channel once they read them. Thats unfortunate since changes in a game of bingo are relevant to all players. Meaning that only one random receiver reading the update for a game would be bad for the other players.

Now I'm using a channel type from the tokio library called "watch". It contains just one value and receivers can await changes and don't remove the value from a channel on reading it. That allows broadcasting changes to all receivers so that all players getting realtime updates about the game.

Next I might look into WebRTC DataChannels to send game updates from client to client without the server in between (mostly).

Is someone else working on a similar problem and has repos to recommend?

Thanks!