Server - Client UDP [node.js]

client.js

/*
========
Client
========
*/

const HOST = 'localhost';
const PORT = 41234;

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

client.on('message', function (msg, rinfo) {
    console.log('recieved: ' + msg.toString('hex'));
    client.close();
});

client.on('err', function (err) {
    console.log('client error: \n' + err.stack);
    console.close();
});

client.on('close', function () {
    console.log('closed.');
});

function send(message, host, port) {
    client.send(message, 0, message.length, port, host, function (err, bytes) {
        console.log('sent.');
    });
}

// var message = new Buffer('hello', 'utf8');
let message = Buffer.from('3031323334353637', 'hex');
send(message, HOST, PORT);

server.js

/*
========
Server
========
*/

const PORT = 41234;
var dgram = require('dgram');
var server = dgram.createSocket('udp4');

server.on('listening', function () {
    var address = server.address();
    console.log('server listening ' + address.address + ':' + address.port);
});

server.on('message', function (msg, rinfo) {
    console.log('server got a message from ' + rinfo.address + ':' + rinfo.port);
    console.log('  HEX  : ', msg.toString('utf8'));
    console.log('  ASCII: ', msg);
    var ack = Buffer.from('ack');
    server.send(ack, 0, ack.length, rinfo.port, rinfo.address, function (err, bytes) {
        console.log('sent ACK.');
    });
});

server.on('error', function (err) {
    console.log('server error: \n' + err.stack);
    server.close();
});

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

server.bind(PORT);