Socket events not firing in browser with docker containers, docker-compose

Question

Without dockerizing the application, everything works properly.

When migrating the application to Docker, I am unable to to receive socket events in the browser.

I am able to receive socket events in the server, from the browser and console.

docker-compose.yml

database:
    image: mongo:latest
    container_name: minipool_database
    ports:
        - "27017:27017"

seed:
    build: seed
    container_name: mp_seed
    links:
        - database

application: (Node v.7.9.0 / socket-io: 1.4.8 / Angular 1.4.9 / angular-socket-io: 0.7.0)
    build: application
    container_name: mp_application
    links:
        - database
    ports:
        - "8080:8080"

Express server

'use strict';

process.env.NODE_ENV = process.env.NODE_ENV || 'development';

var connection = '';

if(process.env.NODE_ENV === 'development') connection = '127.0.0.1:27017/minipool';
if(process.env.NODE_ENV === 'production') connection = 'database:27017/minipool';

var express = require('express'),
    app = express(),
    server = require('http').Server(app),
    io = require('socket.io')(server);

app.use(function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*")
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
    next()
});

app.use(express.static('./'));

app.use(function(req,res,next){
    req.io = io;
    next();
});

server.listen(8080,  function() {});

io.on('connection', function(socket){
    var User = require('./api/model/api.model.user');
    var user_id = '';

    // Update socket id on connection
    socket.on('join', function(data){
        user_id = data._id;
        // Save socket.id on load
    });
});

index.html

script(src='/socket.io/socket.io.js')

angular-socket-io

var socket = options.ioSocket || io.connect();

Answer 1

I knew the way I was passing the socket reference was off, a good example of how something can minimally work.

Passing the socket reference in the request here:

app.use(function(req,res,next){
    req.io = io;
    next();
});

Can be done properly in Express 4:

app.set('socketio', io);

Referenced in a route:

exports.index = function(req, res) {
    var io = req.app.get('socketio');

    io.to(user.sockets[j]).emit("game-update", {
            game: game
        });
});

Sockets are working in Docker containers now.