Authenticate WordPress by Node.js (Socket.IO) ref: http://qiita.com/ryo88c/items/bf255343d6e54259cd2a

auth.js

// For database connection.
var DSN = '';
// WordPress database name.
var WPDB = '';
// Salt constants in wp-config.php.
var LOGGED_IN_KEY = '';
var LOGGED_IN_SALT = '';
// siteurl option in wp_options table.
var SITEURL = 'http://example.com/';

var crypto = require('crypto');
var md5 = crypto.createHash('md5');
var mysql = require('mysql2');
var dbh = mysql.createConnection(DSN);
dbh.connect();
dbh.query('USE ' + WPDB);

io.on('connection', function (socket) {
    var cookies = {};
    socket.request.headers.cookie.split(';').forEach(function(cookie) {
        var parts = cookie.split('=');
        cookies[parts[0].trim()] = (parts[1] || '').trim();
    });
    md5.update(SITEURL, 'utf8');
    var authInfo = unescape(cookies['wordpress_logged_in_' + md5.digest('hex')]).split('|');
    dbh.execute('SELECT * FROM `wp_users` WHERE `user_login` = ?', [authInfo[0]], function(err, res) {
        // Generate hash-key
        var hmac = crypto.createHmac('md5', LOGGED_IN_KEY + LOGGED_IN_SALT);
        hmac.update(res[0].user_login + res[0].user_pass.substr(8, 4) + '|' + authInfo[1]);
        var hashKey = hmac.digest('hex');

        // Generate hmac-hash
        var hmac = crypto.createHmac('md5', hashKey);
        hmac.update(res[0].user_login + '|' + authInfo[1]);
        var hash = hmac.digest('hex');

        if (authInfo[2] === hash) {
            // Authenticated.
            socket.emit('chat message', 'Logged in. Hello ' + res[0].display_name + ' san.');
        }
    });
});