How to MQTT in C#

// For å få uPLibarary til å virke trykker du i visual studio Tool -> NuGet Package Manager -> Manage NuGet Package Solution  -> Browse -> Søk -> Plt.M2Mqtt og install
// På raspberry pi må du laste ned exe filen og M2Mqtt.Net.dll

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;


namespace mqtttest
{
    public partial class Form1 : Form
    {
        MqttClient client;
        string clientId;
        Random rand = new Random();
        public Form1()
        {
            InitializeComponent();

            string BrokerAddress = "192.168.43.208";
            client = new MqttClient(BrokerAddress);

            // register a callback-function (we have to implement, see below) which is called by the library when a message was received
            client.MqttMsgPublishReceived += client_MqttMsgPublishReceived;

            // use a unique id as client id, each time we start the application
            clientId = Guid.NewGuid().ToString();

            client.Connect(clientId);
        }
        protected override void OnClosed(EventArgs e)
        {
            client.Disconnect();

            base.OnClosed(e);
            this.Close();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Button test = (Button)sender;
            test.Text = rand.Next(99999).ToString();
            if (txtTopicSubscribe.Text != "")
            {
                // whole topic
                string Topic = txtTopicSubscribe.Text;

                // subscribe to the topic with QoS 2
                client.Subscribe(new string[] { Topic }, new byte[] { 2 });   // we need arrays as parameters because we can subscribe to different topics with one call
                txtReceived.Text = "";
            }
            else
            {
                MessageBox.Show("You have to enter a topic to subscribe!");
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Button test = (Button)sender;
            test.Text = rand.Next(99999).ToString();
            if (txtTopicPublish.Text != "")
            {
                // whole topic
                string Topic = txtTopicPublish.Text;

                // publish a message with QoS 2
                client.Publish(Topic, Encoding.UTF8.GetBytes(txtPublish.Text), MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE, true);
            }
            else
            {
                MessageBox.Show("You have to enter a topic to publish!");
            }
        }
        void client_MqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
        {
            string ReceivedMessage = Encoding.UTF8.GetString(e.Message);

            txtReceived.Invoke((MethodInvoker)(() => txtReceived.Text = ReceivedMessage));

        }
    }
}