Express / Socket.IO Session Sync

session.js

var cookie = require('cookie');
var cookieParser = require('cookie-parser');

var _sessionStore;
var _sessionSecret;

function plugin(data) {

	// store the Express session cookie name, session store, and session secret for use later
	_sessionCookie = data.name || 'connect.sid';
	_sessionStore = data.store;
	_sessionSecret = data.secret;

	function middleware(socket, next) {

		// create a refreshSession function on the socket
		// this function should be run each time a session needs to be refreshed on the socket
		socket.refreshSession = function(callback) {

			// cookie not found
			if (!socket.handshake.headers.cookie) {
				callback(true, null);
				return;
			}

			var handshakeCookies;
			var handshakeCookie;
			var sessionId;

			try {

				// get the session ID if it exists
				handshakeCookies = cookie.parse(socket.handshake.headers.cookie);
				handshakeCookie = handshakeCookies[_sessionCookie];
				sessionId = cookieParser.signedCookie(handshakeCookies[_sessionCookie], _sessionSecret);

			} catch (e) {
				callback(true, null);
				return;
			}

			// cookie invalid
			// this can happen when the cookie parser can't parse the signed cookie
			if (handshakeCookie === sessionId) {
				callback(true, null);
				return;
			}

			// cookie is signed correctly

			// pull the session information from the session store using the sessionId
			_sessionStore.load(sessionId, function(err, session) {

				if (err || !session) {
					callback(err, session);
					return;
				}

				// add the session data to the socket
				socket.session = session;

				callback(err, session);
				return;

			});

		};

		// run refreshSession on the socket to create the inital session data
		socket.refreshSession(function(err, result) {

			if (err || !result) {
				next();
				return;
			}

			next();
			return;

		});

	}

	return middleware;

}

module.exports = plugin;