signalling-server.js

/**
 * A simple signalling server implementation using socket.io.
 * This socket connection is used a signalling server as WebRTC does not support discovery of other peers.
 * User's audio, video or chat messages does not use this socket.
 */

const channels = {};
const sockets = {};
const peers = {};

const signallingServer = (socket) => {
	const clientAddress = socket.handshake.address;

	socket.channels = {};
	sockets[socket.id] = socket;

	console.log("[" + socket.id + "] connection accepted");
	socket.on("disconnect", () => {
		for (const channel in socket.channels) {
			part(channel);
		}
		console.log("[" + socket.id + "] disconnected");
		delete sockets[socket.id];
	});

	socket.on("join", (config) => {
		console.log("[" + socket.id + "] joined. Channel: ", config.channel);
		const channel = config.channel;

		// Already Joined
		if (channel in socket.channels) return;

		if (!(channel in channels)) channels[channel] = {};

		if (!(channel in peers)) peers[channel] = {};

		peers[channel][socket.id] = { userData: config.userData };

		for (const id in channels[channel]) {
			channels[channel][id].emit("addPeer", {
				peer_id: socket.id,
				should_create_offer: false,
				channel: peers[channel],
			});
			socket.emit("addPeer", { peer_id: id, should_create_offer: true, channel: peers[channel] });
		}

		channels[channel][socket.id] = socket;
		socket.channels[channel] = channel;
	});

	socket.on("updateUserData", async (config) => {
		const channel = clientAddress + config.channel;
		const key = config.key;
		const value = config.value;
		for (let id in peers[channel]) {
			if (id == socket.id) {
				peers[channel][id]["userData"][key] = value;
			}
		}
	});

	const part = (channel) => {
		// Socket not in channel
		if (!(channel in socket.channels)) return;

		delete socket.channels[channel];
		delete channels[channel][socket.id];

		delete peers[channel][socket.id];
		if (Object.keys(peers[channel]).length == 0) {
			// last peer disconnected from the channel
			delete peers[channel];
		}

		for (const id in channels[channel]) {
			channels[channel][id].emit("removePeer", { peer_id: socket.id });
			socket.emit("removePeer", { peer_id: id });
		}
	};

	socket.on("relayICECandidate", (config) => {
		let peer_id = config.peer_id;
		let ice_candidate = config.ice_candidate;

		if (peer_id in sockets) {
			sockets[peer_id].emit("iceCandidate", { peer_id: socket.id, ice_candidate: ice_candidate });
		}
	});

	socket.on("relaySessionDescription", (config) => {
		let peer_id = config.peer_id;
		let session_description = config.session_description;

		if (peer_id in sockets) {
			sockets[peer_id].emit("sessionDescription", {
				peer_id: socket.id,
				session_description: session_description,
			});
		}
	});
};

module.exports = signallingServer;