Socket (module socket.io)

const io = require('socket.io')(http);
io.on('connection',onConnection);

function onConnection(socket) {   
  socket.emit('message',"hello from server");
  socket.on('message',function(message){onMessage(message,socket)});
}
function onMessage(message,socket) {
  console.log('Server received message from client '+message);
}

const socket = io.connect('http://localhost:8000');
socket.on('message',receiveMessageEvent);
socket.emit('message',"Hello from client");
function receiveMessageEvent(message) {
  console.log('Client received message from server: '+message);
}