index-ws.js

const express = require("express");
const server = require("http").createServer();
const app = express();

app.get("/", function (req, res) {
  res.sendFile("index.html", { root: __dirname });
});

server.on("request", app);
server.listen(3000, function () {
  console.log("server listen to port 3000");
});

/**  Begin websocket*/
const WebSocketServer = require("ws").Server;

const wss = new WebSocketServer({ server: server });

wss.on("connection", function connection(ws) {
  const numClients = wss.clients.size;

  console.log("clients connected: ", numClients);

  wss.broadcast(`Current visitors: ${numClients}`);

  if (ws.readyState === ws.OPEN) {
    ws.send("welcome!");
  }

  ws.on("close", function close() {
    wss.broadcast(`Current visitors: ${wss.clients.size}`);
    console.log("A client has disconnected");
  });

  ws.on("error", function error() {
    //
  });
});

/**
 * Broadcast data to all connected clients
 * @param  {Object} data
 * @void
 */
wss.broadcast = function broadcast(data) {
  console.log("Broadcasting: ", data);
  wss.clients.forEach(function each(client) {
    client.send(data);
  });
};
/** End Websocket *****/