node/test/simple/test-dgram-pingpong.js

common = require("../common");
assert = common.assert
var Buffer = require('buffer').Buffer;
var dgram = require("dgram");

var tests_run = 0;

function pingPongTest (port, host) {
  var callbacks = 0;
  var N = 500;
  var count = 0;
  var sent_final_ping = false;

  var server = dgram.createSocket("udp4", function (msg, rinfo) {
    console.log("server got: " + msg + " from " + rinfo.address + ":" + rinfo.port);

    if (/PING/.exec(msg)) {
      var buf = new Buffer(4);
      buf.write('PONG');
      server.send(buf, 0, buf.length, rinfo.port, rinfo.address, function (err, sent) {
        callbacks++;
      });
    }
  });

  server.on("error", function (e) {
    throw e;
  });

  server.on("listening", function () {
    console.log("server listening on " + port + " " + host);

    var buf = new Buffer('PING'), 
        client = dgram.createSocket("udp4");

    client.addListener("message", function (msg, rinfo) {
      console.log("client got: " + msg + " from " + rinfo.address + ":" + rinfo.port);
      assert.equal("PONG", msg.toString('ascii'));

      count += 1;

      if (count < N) {
        client.send(buf, 0, buf.length, port, "localhost");
      } else {
        sent_final_ping = true;
        client.send(buf, 0, buf.length, port, "localhost");
        process.nextTick(function() {
          client.close();
        });
      }
    });

    client.on("close", function () {
      console.log('client has closed, closing server');
      assert.equal(N, count);
      tests_run += 1;
      server.close();
      assert.equal(N-1, callbacks);
    });

    client.on("error", function (e) {
      throw e;
    });

    console.log("Client sending to " + port + ", localhost " + buf);
    client.send(buf, 0, buf.length, port, "localhost", function (err, bytes) {
      if (err) {
        throw err;
      }
      console.log("Client sent " + bytes + " bytes");
    });
    count += 1;
  });
  server.bind(port, host);
}

// All are run at once, so run on different ports
pingPongTest(20989, "localhost");
pingPongTest(20990, "localhost");
pingPongTest(20988);
//pingPongTest("/tmp/pingpong.sock");

process.addListener("exit", function () {
  assert.equal(3, tests_run);
  console.log('done');
});