server.js

// Inspired by https://gist.github.com/icebob/0dda386fceb8e14b91d84d057fac676f
"use strict";

// Create express app
const express = require("express");
const app = express();
var http = require('http').Server(app);
var path = require('path');

// Generate webpack config with CLI service
if (process.env.NODE_ENV !== 'production') {
  const webpackConfig = require("@vue/cli-service/webpack.config.js");

  // Configure webpack as middleware
  const webpack = require("webpack");

  webpackConfig.entry.app.unshift('webpack-hot-middleware/client');
  webpackConfig.plugins.push(new webpack.HotModuleReplacementPlugin())
  //console.log(webpackConfig);
  const compiler = webpack(webpackConfig);
  const devMiddleware = require('webpack-dev-middleware'); // eslint-disable-line
  app.use(devMiddleware(compiler, {
      publicPath: webpackConfig.output.publicPath,
      headers: { "Access-Control-Allow-Origin": "*" },
      stats: {colors: true}
  }));

  const hotMiddleware = require('webpack-hot-middleware'); // eslint-disable-line
  app.use(hotMiddleware(compiler, {
      log: console.log
  }));
}
else {
  app.use(express.static(path.join(__dirname, 'dist/')));
  app.get('/', function (req, res) {
    res.sendFile(path.join(__dirname, 'dist/index.html'));
  });
}


const io = require('socket.io')(http, {cookie: false});

// Store data in an object to keep the global namespace clean and 
// prepare for multiple instances of data if necessary
function Data() {
  this.orders = {};
}

/*
  Adds an order to to the queue
*/
Data.prototype.addOrder = function (order) {
  //Store the order in an "associative array" with orderId as key
  this.orders[order.orderId] = order;
};

Data.prototype.getAllOrders = function () {
  return this.orders;
};

let data = new Data();

io.on('connection', function (socket) {

  // Send list of orders when a client connects
  socket.emit('currentQueue', { orders: data.getAllOrders() });

  // When a connected client emits an "addOrder" message
  socket.on('addOrder', function (order) {
    data.addOrder(order);
    // send updated info to all connected clients, note the use of io instead of socket
    io.emit('currentQueue', { orders: data.getAllOrders() });
  });

  // When a connected client emits an "clearQueue" message
  socket.on('clearQueue', function () {
    data = new Data();
    // send updated info to all connected clients, note the use of io instead of socket
    io.emit('currentQueue', { orders: data.getAllOrders() });
  });

});

const PORT = process.env.PORT || 8080;
http.listen(PORT, function() {
    console.log("Developer server running on http://localhost:" + PORT);
});