How to start express and websocket server in same port in NodeJS?

How to use the same port to start the web server (express) and web socket server in the same port in NodeJS ?

//app.js
var WebSocketServer = require('ws').Server
    , http = require('http')
    , express = require('express')
    , app = express();
app.use(express.static(__dirname + '/'));
var server = http.createServer(app);
var wss = new WebSocketServer({server:server});
wss.on('connection', function (ws) {
    ws.on('close', function () {
        console.log('close:');
    });
    ws.on('message', function (message) {
        console.log('message:', message);
    });
});
server.listen(3000);