wsserver.js

const WebSocket = require('ws');  // npm install -g ws
const server = new WebSocket.Server({port: 8000}, function() {
  console.log('WS server started');
});
server.on('connection', function connection(ws, req) {
  let i = 0;
  ws.on('message', function incoming(message) {
    console.log('received', message);
  });
  console.log('connected', req.connection.remoteAddress);
  let t = setInterval(() => {
    const msg = 'hi' + i++;
    ws.send(msg);
    console.log('sent', msg);
  }, 1000);
  ws.on('close', () => {
    console.log('close');
    clearInterval(t);
  })
});