chrome-extensions-samples/apps/samples/udp/server/dropping-server.js

/*
 *  Node.js UDP echo server
 *
 *  This demonstration shows a basic echo server that has randomly drops responses.
 *  The drop factor is `threshold` 0.9 = 90% chance of succes, 10% dropped packets
 * 
 *  Additionally each response is delayed by 2-3 seconds.
 * 
 *  Listens on port 3007 by default. Pass in a desired port as cmdline argument.
 */

var dgram = require('dgram');
var server = dgram.createSocket('udp4');

var threshold = 0.99;

server.on("listening", function() {
  var address = server.address();
  console.log("Listening on " + address.address);
});

server.on("message", function(message, rinfo) {
  var delay = 2000+Math.random()*1000;
  // Echo the message back to the client.
  var dropped = Math.random();
  if(dropped > threshold) {
    console.log("Recieved message from: " + rinfo.address + ", DROPPED");
    return;
  }
  console.log("Recieved message from: " + rinfo.address);
  setTimeout(function() {
    server.send(message, 0, message.length, rinfo.port, rinfo.address, function(err, bytes) {
      console.log(err, bytes); 
    });
  }, delay);
});

server.on("close", function() {
  console.log("Socket closed");
});

var port = process.argv[2];
server.bind(port ? parseInt(port) : 3007);