Signaling

Before two pages can connect directly, they exchange a few messages through a server: who is on the site, the descriptions of their connections, and the addresses they can be reached at. That is signaling. After that, files go straight from one browser to the other, and the server sees none of them.

PeerPlugin takes any peer-data signaling as its signaling option.

peer-cdn’s server

peer-cdn/server is a signaling server on socket.io 4. Attach it to a Node.js HTTP or HTTPS server:

import { createServer } from 'node:http';
import { attachSignaling } from 'peer-cdn/server';

const server = createServer();
attachSignaling(server, { cors: { origin: 'https://www.example.com' } });
server.listen(8080);

The second argument is socket.io’s server options; allow your site’s origin in cors when the server is on another origin. attachSignaling returns the socket.io Server, to add whatever your site needs, such as authentication or rate limits.

It routes peer-data’s messages by their type, room and ids, and never reads what they carry:

• a page joining or leaving goes to the others in the room;
• offers, answers and ICE candidates go to the one page they are for, and only in the room the sender joined;
• each socket speaks only for the ids it joined with, 16 at most, and when it drops, the others in its rooms hear that it left;
• a page whose connection drops reconnects and asks for its id again, often before the server has noticed its old socket is gone. It gets the id back once the server does, within socket.io’s ping interval and timeout: 45 seconds by default.

Pages reach it with SocketChannel, which peer-cdn takes from peer-data, over a socket.io-client 4 socket:

import { io } from 'socket.io-client';
import { PeerPlugin, SocketChannel } from 'peer-cdn';

new PeerPlugin({ signaling: new SocketChannel(io('https://signaling.example.com')) });

Any peer-data peers can use the same server. While you develop with Vite, the plugin runs it on Vite’s own server.

ICE servers

Pages on different networks need ICE servers to find a way through routers and firewalls. Pass them in configuration:

new PeerPlugin({
  signaling,
  configuration: { iceServers: [{ urls: 'stun:stun.l.google.com:19302' }] },
});

A STUN server lets most visitors connect directly. Those behind stricter networks need a TURN server to relay their traffic; add it to iceServers with its credentials. Visitors who can’t connect still get every file from your server.

Between tabs

BroadcastChannelSignaling reaches the pages of one browser with no server. The live demo uses it; a real site needs a server, since its visitors are in different browsers.

Your own

Signaling is an object with a send and a subscribe, so any transport that routes the messages between pages works: see Your own in peer-data’s guide.