server.js

'use strict';
const express = require('express');
const app = express();
const http = require('http');
const cors = require('cors');
const session = require('express-session');
const bodyParser = require('body-parser');
const cookieParser = require('cookie-parser');
const expressSwagger = require('express-swagger-generator')(app);
const srvConfig = require('./config');
const mongoose = require('mongoose');
const {CONNECTION_TYPE, DB_HOST, DB_USERNAME, DB_PASSWORD, DB_PORT, DB_NAME, DB_QUERY_PARAMS} = srvConfig;
const dbAuthString = (DB_USERNAME && DB_PASSWORD) ? `${srvConfig.DB_USERNAME}:${srvConfig.DB_PASSWORD}@` : '';
let httpServer;

/**
 * Configure middleware
 */
app.use(
    cors({
        // origin: `http://localhost:${srvConfig.SERVER_PORT}`,
        origin: function (origin, callback) {
            return callback(null, true)
        },
        optionsSuccessStatus: 200,
        credentials: true
    }),
    session({
        saveUninitialized: true,
        secret: srvConfig.SESSION_SECRET,
        resave: true
    }),
    cookieParser(),
    bodyParser.json()
);

/**
 * Include all API Routes
 */
app.use('/api', require('./routes/api'));

/**
 * Swagger UI documentation
 */
if (srvConfig.SWAGGER_SETTINGS.enableSwaggerUI)
    expressSwagger(srvConfig.SWAGGER_SETTINGS);

/**
 * Configure http(s)Server
 */
if (srvConfig.HTTPS_ENABLED) {
    const privateKey = fs.readFileSync(srvConfig.PRIVATE_KEY_PATH, 'utf8');
    const certificate = fs.readFileSync(srvConfig.CERTIFICATE_PATH, 'utf8');
    const ca = fs.readFileSync(srvConfig.CA_PATH, 'utf8');

    // Create a HTTPS server
    httpServer = https.createServer({key: privateKey, cert: certificate, ca: ca}, app);
} else {
    // Create a HTTP server
    httpServer = http.createServer({}, app);
}

/**
 * Start http server & connect to MongoDB
 */
httpServer.listen(srvConfig.SERVER_PORT, () => {
    mongoose.connect(`${CONNECTION_TYPE}://${dbAuthString}${DB_HOST}:${DB_PORT}/${DB_NAME}${DB_QUERY_PARAMS}`, {
        useNewUrlParser: true,
        useUnifiedTopology: true
    }, () => {
        console.log(`Server started on port ${srvConfig.SERVER_PORT}`);
    });
});

/**
 * Socket.io section
 */
const io = require('socket.io')(httpServer);
io.on('connection', function (socket) {
    console.log(`New connection: ${socket.id}`);

    socket.on('disconnect', () => console.log(`Connection left (${socket.id})`));
});