node code to verify & listen facebook real time subscription events

gistfile1.js

var qs = require('querystring');

var verifyToken = 'tekken';

var processRequest = function(req, callback) {
    var body = '';
    req.on('data', function (data) {
        body += data;
    });
    req.on('end', function () {
        callback(qs.parse(body));
    });
}

var http = require('http');
http.createServer(function (req, res) {
    console.log("got a request")
    processRequest(req, function(data) {
        console.log("data:" + JSON.stringify(data));
        console.log("req method is:" + req.method);

        if (req.method === 'GET') {
            var queryString = req.url.split('?')[1];
            var params = qs.parse(queryString);
            console.log(params);
            if (params["hub.mode"] === 'subscribe' && params["hub.verify_token"] === verifyToken) {
                res.end(params["hub.challenge"]);
            } else {
                res.end("invalid GET request")
            }
        } else {
            res.end(JSON.stringify(data));
        }
    });
}).listen(1337, "127.0.0.1");
console.log('Server running at http://127.0.0.1:1337/');