app.js

var client = require('./client.js')('127.0.0.1', 3000);

client.sendMessage("new_player");

client.js

var dgram = require('dgram')

module.exports = function(host, port) {
    return new Client(host, port);
}

function Client(host, port)
{
    this.client = dgram.createSocket('udp4');
    this.port = port;
    this.host = host;

    this.init();
}

Client.prototype.init = function() {

    this.client.on('listening', () => {
        var address = this.client.address();
        console.log(`client listening to ${address.host}:${address.port}`);
    })

    this.client.on('message', function(message,remote) {
        this.gotMessage(message, remote);
    });
}

Client.prototype.gotMessage = function(message, remote) {

    console.log(`Got message "${message}" from "${remote.address}:${remote.port}"`);
}

Client.prototype.sendMessage = function (msg) {
    var message = new Buffer(msg);

    this.client.send(message, 0, message.length, this.port, this.host, function (err, bytes) {
        if(err) throw err;

        console.log("UDP message sent to " + this.host + ":" + this.port);
    })
}