@boardgame.io/p2p

Experimental peer-to-peer multiplayer transport for boardgame.io

This package provides an experimental multiplayer transport implementation, which establishes a peer-to-peer connection between clients. Instead of using a Node.js server to maintain authoritative match state and communicate between clients, a host client maintains the authoritative state in their browser and manages connections between all the connected peers.

Installation

npm install @boardgame.io/p2p

Usage

import { Client } from 'boardgame.io/client';
import { P2P } from '@boardgame.io/p2p';
import { MyGame } from './game';

const matchID = 'random-id-string';

// Host clients maintain the authoritative game state and manage
// communication between all other peers.
const hostClient = Client({
  game: MyGame,
  matchID,
  playerID: '0',
  multiplayer: P2P({ isHost: true }),
});

// Peer clients look up a host using the `matchID` and communicate
// with the host much like they would with a server.
const peerClient = Client({
  game: MyGame,
  matchID,
  playerID: '1',
  multiplayer: P2P(),
});

API

P2P(options?)

You can configure the peer-to-peer transport by passing an optional object. It can contain the following fields.

• isHost

  • type: boolean
  • default: false

  Controls whether or not this instance is a host and controls the authoritative game state. Only one client should have isHost: true.

• onError

  • type: (error: Error) => void
  • default: undefined

  Callback to subscribe to PeerJS’s 'error' event.

• peerOptions

  • type: PeerJSOption
  • default: undefined

  Passed to PeerJS when creating a new Peer connection. See PeerJS docs for full list of options →

Authenticating players

By default, any client can connect with any playerID and successfully submit moves as that player. If you want to avoid this, you must set credentials on your boardgame.io clients. The first client to connect with a given playerID will authenticate and all future connections for that playerID must also provide the same credentials to successfully connect.

The transport uses public-key encryption, deterministically generating keys from the value of credentials. For optimal security, use the included helper method to generate credentials:

import { Client } from 'boardgame.io/client';
import { P2P, generateCredentials } from '@boardgame.io/p2p';

const credentials = generateCredentials();

const peerClient = Client({
  multiplayer: P2P(),
  credentials,
  // ...
});

Notes

What does experimental mean?

This package currently works but is liable to change as what is required for peer-to-peer scenarios is better understood. Please try it out and send us feedback, bug reports and feature requests, but be aware that it may change in breaking ways until a more stable API is established.

Why would I want to use this?

Deploying a Node server to enable multiplayer play can be a serious logistical hurdle and is often more expensive than serving a static website. This transport enables multiplayer play without a game server. If you’re looking for a casual way to play with friends that can be pretty attractive.

What are the drawbacks?

No lobby or matchmaking. You have to have a matchID to find and connect to the other players. One pattern might be for a host to generate a random matchID on your site. Then they could share the matchID with friends via their preferred instant messaging service for example.

Additionally, currently if the host goes offline, the match will stop and potentially all match state will be lost. In the future it may be possible to decentralise this and allow other players to step in as hosts in this case.

How does this work?

Under the hood this transport uses PeerJS, a library that helps simplify creating peer-to-peer connections. When a host starts running, it registers with a so-called “handshake” server using a matchID to identify itself. Then when other clients connect, they can use the same matchID to request a connection to the host from the handshake server. Once that peer-to-peer connection is established between clients, all future communication will take place directly between clients and no longer pass via a server.

Unless configured otherwise, this transport will use PeerJS’s default handshake server to negotiate the initial connection between peers. Consider running your own handshake server or donating to PeerJS to help support theirs.

Contributing

Bug reports, suggestions, and pull requests are very welcome! If you run into any problems or have questions, please open an issue.

Please also note the code of conduct and be kind to each other.

License

The code in this repository is provided under the MIT License.