echoServer.js

const net = require('net')
const port = 7070
const host = '127.0.0.1'

const server = net.createServer()
server.listen(port, host, () => {
  console.log('TCP Server is running on port ' + port + '.')
})

let sockets = []

server.on('connection', function(sock){
  console.log('CONNECTED: ' + sock.remoteAddress + ':' + sock.remotePort)
  sockets.push(sock)

  sock.on('data', function(data){
    console.log('DATA ' + sock.remoteAddress + ' : ' + data)
    // Write the data back to all the connected, the client will receive it as data from the server
    sockets.forEach(function (sock, index, array) {
      sock.write(sock.remoteAddress + ':' + sock.remotePort + "said" + data + '\n')
    })
  })

  // Add a 'close' event handler to this instance of socket
  sock.on('close', function(data){
    let index = sockets.findIndex(function(o){
      return o.remoteAddress === sock.remoteAddress && o.remotePort ===sock.remotePort
    })
    if(index !== -1) sockets.splice(index, 1)
    console.log('CLOSED:' + sock.remoteAddress + ' ' + sock.remotePort)
  })
})