Backend for .io Games

How the API maps to .io play

• Instant accounts — one register call creates a player with a nickname; the credential persists in localStorage, so "just play" still means persistent stats on return.
• Drop-in lobbies — matchmaking endpoints list open lobbies and put players into them; 1v1 duels through 50-player arenas are the same code path with different max_players.
• Realtime sync — the WebSocket lane relays room traffic peer-to-peer through the server; no game server process to run, scale or patch.
• Built-in leaderboards — scores live in player data; ranked queries return the top list that keeps .io players coming back.
• Moderation included — nickname and chat screening is server-side and free; an .io game with unmoderated names won't survive its first front-page day.

The 15-line core loop

import { MultiplayerClient } from 'michitai-multiplayer';
const mp = new MultiplayerClient(API_TOKEN);

const token = localStorage.mp_token ??= (await mp.players
  .register(nickname)).private_key;

const lobbies = await mp.matchmaking.list();
const { matchmaking_id } = lobbies.matchmaking[0];
await mp.matchmaking.join(token, matchmaking_id);

const rt = mp.createRealtime({ onReceive: applyState });
await rt.connect((await mp.realtime.get(token)).token);
setInterval(() => rt.send('all', 'pos', myPosition), 50);

Honest limits

Browser .io games send on the WebSocket lane only — no browser UDP. For high-rate twitch arenas, host authoritative game logic server-side (your Node.js server can use the same SDK with the UDP lane) and use rooms/matchmaking here for the lobby shell. Slower arenas, .io-style card/party variants and 1v1 duels run entirely on the WS lane — see WebGL & browser games for the transport detail.