Socket.io does not work [duplicate] - node.js

Question

My app.js
const express = require('express'),
morgan = require('morgan'),
bodyParser = require('body-parser'),
path = require('path'),
mongoose = require('mongoose'),
app = express(),
config = require('./config'),
Note = require('./models/note'),
server = require('http').createServer(app),
io = require('socket.io')(server),
socket = io.socket;
mongoose.connect('mongodb://'+config.db.host+'/'+config.db.name);
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
// Serve static assets
app.use(express.static(path.resolve(__dirname, '..', 'build')));
app.use(function(req, res, next) {
const allowedOrigins = [
'http://127.0.0.1:8000',
'http://localhost:8000',
'http://127.0.0.1:3000',
'http://localhost:3000'];
const origin = req.headers.origin;
if(allowedOrigins.indexOf(origin) > -1){
res.setHeader('Access-Control-Allow-Origin', origin);
}
//res.header("Access-Control-Allow-Origin", "127.0.0.1 localhost");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
res.header('Access-Control-Allow-Credentials', true);
next();
});
calling socket.emit() in handlers after above codes.
My index.js
'use strict';
const app = require('./app'),
// server = http.createServer(app),
PORT = process.env.PORT || 8000;
app.listen(PORT, () => {
console.log(`REST API running on ${PORT}!`);
});
Console output:
Any idea? Thanks

Answer 1

If you're going to do this:
server = require('http').createServer(app),
Then, you can't do:
app.listen(PORT, ...);
because app.listen() will create a new and different server and socket.io will not be associated with that one.
Instead, you need to do:
server.listen(PORT, ...)
using the server value from app.js. And, if you want to require() in the server from app.js, you also need to export it from app.js (something else I don't see your code doing).
For reference, the code for app.listen(), does this:
app.listen = function listen() {
var server = http.createServer(this);
return server.listen.apply(server, arguments);
};
You can see how it creates a different server than the one you passed to socket.io. Thus the one you passed to socket.io is never started and thus socket.io does not work.