open wechat verify with node js

wechat-server.js

// run it using ngrok
var url = require('url'),
    crypto = require('crypto'),
    querystring = require('querystring'),

    http = require('http'),
    port = 3000;

var token = '***your token';

http.createServer(function(req, res) {
  if (req.method === 'GET') {
    var queryObj = querystring.parse(url.parse(req.url).query);
    var signature = queryObj.signature,
        timestamp = queryObj.timestamp,
        nonce = queryObj.nonce,
        echostr = queryObj.echostr;

    var sha1 = crypto.createHash('sha1'),
        sha1Str = sha1.update([token, timestamp, nonce].sort().join('')).digest('hex');

    console.log("my signature: " + sha1Str);

    res.writeHead(200, {'Content-Type': 'text/plain'});
    return res.end((sha1Str === signature) ? echostr : '');
  }

  res.end();
}).listen(port);