Simplest example of sending data from client to server in localhost network

client (website)

<script src="socket.io.min.js"></script>
<script>
  var ipOfLaptop = '192.168.2.107';
  var definedPort = 8123;
  var host = 'http://' + ipOfLaptop + ':' + definedPort;

  var socket = io(host);
  socket.emit('msg', 'test');
</script>

server (nodeJS)

var definedPort = 8123;
var ioIn = require('socket.io').listen(definedPort);
ioIn.on('connection', function(socketIn) {
  socketIn.on('msg', function(msg) {
    console.log('msg', msg);
  });
});