server.js

require('dotenv').config({ path: '.env/.env' });
var express      = require('express'),
  fileUpload     = require('express-fileupload');
  app            = express(),
  appPort        = process.env.APP_RESTPORT || 3000,
  bodyParser     = require('body-parser'),
  cors           = require('cors'),
  os             = require("os"),
  fs             = require('fs'),
  socketioJwt   = require('socketio-jwt');

const { Server } = require("socket.io");
const { setupSocketController } = require('./api/controllers/socketController');
var httpOptions  = {}

if(process.env.APP_SSL_ENABLED == 1){
  var http    = require('https');
  httpOptions = {
    key: fs.readFileSync('init_scripts/ssl-certs/output/private/server.key'),
    cert: fs.readFileSync('init_scripts/ssl-certs/output/certs/server.crt')
  };
}else{
  var http = require('http');
}

const server = http.createServer(httpOptions, app).listen(appPort, function (req, res) { 
  console.log(`Server started at port ${appPort}`); 
});

// Create & Init Socket App
const io = new Server(server, {
  transports: ['websocket'], //required nginx proxy
  cors: {
    origin: '*',
  },
  allowEIO3: true
});

// Setup socket controller
setupSocketController(io);

api/controllers/socketController.js

// socketController.js
var socketioJwt = require('socketio-jwt');

const privateKey    = fs.readFileSync(process.env.APP_PRIVATE_KEY, "utf8");
// const publicKey     = fs.readFileSync(process.env.APP_PUBLIC_KEY, "utf8");

module.exports.setupSocketController = (io) => {
  io.use(socketioJwt.authorize({
    secret: privateKey,
    handshake: true
  }));

  io.on('connection', (socket) => {
      // const clientSourceIp  = socket.request.headers['x-forwarded-for'] || socket.request.socket.remoteAddress || null;
      // console.log(`${socket.id} => ${clientSourceIp} is connected`);
      let __createdtime__ = Date.now(); // Current timestamp

      // Add a user to a room
      socket.on('ping', (data) => {
        socket.emit('pong', {
          __createdtime__
        });
      });

      socket.on('disconnect', (data) => {
      // console.log(`${socket.id} => ${clientSourceIp} is disconnected`);
      let __createdtime__  = Date.now(); // Current timestamp
      const { room }       = data; // Data sent from client when join_room event emitted
      // Send message to all users currently in the room, apart from the user that just joined
        socket.to(room).emit('general_messages', {
          message: `${socket.id} disconnected`,
          __createdtime__,
        });
      });
  });

  // Emit broadcast from outside the connection block
  const broadcastMessage = (event, message) => {
    io.emit(event, message);
  };

  // Export the function if needed elsewhere
  module.exports.broadcastMessage = broadcastMessage;
};

api/controllers/anothercontroller.js

const { broadcastMessage } = require('../controllers/socketController');

exports.retrieveAll = async function(req, res) {
  broadcastMessage('pong', {"pong-test": "test-pong-controller"});
}

The goal is when ever a controller completes a transaction it will send broadcast message to connected socket clients.

This works with local machine but in remote server no longer works..

Uses Nginx as web server.

# For more information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

# Load dynamic modules. See /usr/share/doc/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;

events {
    worker_connections 1024;
}

http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 4096;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;

    upstream backends {
        ip_hash;
        server 127.0.0.1:3000;
    }

    server {
        listen       443 ssl http2;
        listen       [::]:443 ssl http2;
        server_name  example.com;
        client_max_body_size 1G;
        
        ssl_certificate "/etc/letsencrypt/live/example.com/fullchain.pem";
        ssl_certificate_key "/etc/letsencrypt/live/example.com/privkey.pem";
        include /etc/letsencrypt/options-ssl-nginx.conf;
        ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;

        location /socket.io/ {
            proxy_pass https://backends;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header Host $host;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_cache_bypass $http_upgrade;
            proxy_read_timeout 60s;

            proxy_ssl_verify off;
            proxy_ssl_server_name on;
        }

        location / {
            proxy_pass https://backends;
            # Ensure HTTP/2 is properly handled
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header Host $host;
            proxy_cache_bypass $http_upgrade;

            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            proxy_ssl_verify off;
            proxy_ssl_server_name on;

            proxy_set_header X-Client-Proto $scheme;
            proxy_set_header X-Client-Proto-Ver $server_protocol;
            proxy_set_header X-Real-IP $remote_addr;

            proxy_pass_request_headers on;
            proxy_set_header Cookie $http_cookie;

            # Change Set-Cookie headers if necessary
            proxy_cookie_domain example.com .example.com;

            # Handle path rewriting for cookies
            # proxy_cookie_path /backend/ /;
        }
    }
}