need help setting up socket.io into my node server

so I'm tried to put socket.io into my node server in order to make a messaging function for my app but having problem getting to function despite doing test app correct. Not sure where the problem is exactly?

server.js

var path = require('path');
var qs = require('querystring');

var async = require('async');
var bcrypt = require('bcryptjs');
var bodyParser = require('body-parser');
var colors = require('colors');
var cors = require('cors')
var fs = require('fs');
var express = require('express');
var http = require('http');
var https = require('https');
var logger = require('morgan');
var jwt = require('jwt-simple');
var moment = require('moment');
var mongoose = require('mongoose');
var multer = require('multer');
var request = require('request');
var upload = multer({ dest: 'uploads/' });

var config = require('./config');

..
a bunch of code for mongoose


 var app = express();


var server = require('http').createServer(app);
var io = require('socket.io')(server);


io.on('connection', function(socket){
    console.log('a user connected');
});

..
ssl setup 

// Create an HTTP service.
http.createServer(app).listen(8000); // opens the port
// Create an HTTPS service identical to the HTTP service.
https.createServer(options, app).listen(4433); // for the ssl

index.html

..bunch of code like bootstrap and angular.js

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.1/socket.io.js"></script>
<script>
    var socket = io.connect('http://localhost:8000');
    socket.on('connect', function(data) {
        socket.emit('join', 'Hello World from client');
    });
</script>

so when I tried to run the site on localhost:8000. In the console, it send back GET /socket.io/?EIO=3&transport=polling&t=LnM0Fd3 404. I'm not sure what went wrong with the set up process of socket.io

via Jason Tran