udp_node_client.js

localhost';
var PORT = 9999;

var Buffer = require('buffer').Buffer,
    dgram = require("dgram");

var client = dgram.createSocket();

var buf = new Buffer(4);
buf.write('PING');

console.log("Sending " + buf + " to " + HOST + ":" + PORT);
client.send(PORT, 'localhost', buf, 0, buf.length);

process.nextTick(function() {
  process.exit();
});

udp_node_server.js

var HOST = 'localhost',
    PORT = 9999;

var dgram = require("dgram");

var server = dgram.createSocket(function (msg, rinfo) {
  console.log("connection from " + rinfo.address + ":"+ rinfo.port);
  console.log("server got: " + msg);
  server.close();
});

server.bind(PORT, HOST);

server.addListener("listening", function () {
  console.log("server listening on " + HOST + ":" + PORT);
});