NodeJS basic tcp socket client and server without external library

socket.js

// nodejs provided this example already on https://nodejs.org/api/http.html#http_event_upgrade
// I changed some stuffs so I can understand it better.

const http = require('http');

// Create an HTTP server
const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('okay');
});

// upgrade to websocket
server.on('upgrade', (req, socket, head) => {
  socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\r\n' +
               'Upgrade: WebSocket\r\n' +
               'Connection: Upgrade\r\n' +
               '\r\n');
    
  // recieve the buffer that is sent from client and send it back,
  // I don't use socket.pipe so i can get more understanding about it.
  socket.on("data",buffer => {
    console.log(buffer.toString())
    socket.write(buffer.toString())
  })
});

// Now that server is running
server.listen(1337, '127.0.0.1', () => {

  // make a request
  const options = {
    port: 1337,
    host: '127.0.0.1',
    headers: {
      'Connection': 'Upgrade',
      'Upgrade': 'websocket'
    }
  };

  const req = http.request(options);
  req.end();

  req.on('upgrade', (res, socket, upgradeHead) => {
    console.log('got upgraded!');
    
    // send text buffer to server
    socket.write("DATA FROM CLIENT");
    socket.on("data", buffer =>  console.log(buffer.toString()))
  });
});