Node.js udp server example http://wp.me/p2fInN-tA

MyUDPServer.js

// port to listen to
var PORT = xxxxx; // Change to your port number

// x's should be replaced with your EC2 private ip
var HOST = 'ip-xxx-xx-xx-xxx.your-region.compute.internal';

// Load datagram module
var dgram = require('dgram');

// Create a new instance of dgram socket
var server = dgram.createSocket('udp4');

/**
Once the server is created and binded, some events are automatically created.
We just bind our custom functions to those events so we can do whatever we want.
*/

// Listening event. This event will tell the server to listen on the given address.
server.on('listening', function () {
    var address = server.address();
    console.log('UDP Server listening on ' + address.address + ":" + address.port);
});

// Message event. This event is automatically executed when this server receives a new message
// That means, when we use FUDPPing::UDPEcho in Unreal Engine 4 this event will trigger.
server.on('message', function (message, remote) {
    console.log('Message received from ' + remote.address + ':' + remote.port +' - ' + message.toString());
    server.send(message, 0, message.length, remote.port, remote.address, function(err, bytes) {
	  if (err) throw err;
	  console.log('UDP message sent to ' + remote.address +':'+ remote.port + '\n');
	});
});

// Error event. Something bad happened. Prints out error stack and closes the server.
server.on('error', (err) => {
  console.log(`server error:\n${err.stack}`);
  server.close();
});

// Finally bind our server to the given port and host so that listening event starts happening.
server.bind(PORT, HOST);