.NET(C#)

.Net Example

using System;
using System.Threading;
using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;

class MqttClientExample
{
    private MqttClient client;
    private string broker;
    private int port;
    private string topic;
    private string clientId;
    private string username;
    private string password;
    private byte qos;
    private bool isReconnecting = false;

    // Constructor to initialize MQTT connection parameters
    public MqttClientExample(string broker, int port, string topic, string clientId, string username, string password, byte qos)
    {
        this.broker = broker;
        this.port = port;
        this.topic = topic;
        this.clientId = clientId;
        this.username = username;
        this.password = password;
        this.qos = qos;
    }

    // Method to connect to the MQTT server
    public void Connect()
    {
        try
        {
            // Create an MQTT client instance
            client = new MqttClient(broker, port, false, null, null, MqttSslProtocols.None);

            // Subscribe to the connection closed event
            client.ConnectionClosed += Client_ConnectionClosed;

            // Connect to the MQTT server
            client.Connect(clientId, username, password);

            if (client.IsConnected)
            {
                Console.WriteLine("Successfully connected to the MQTT server.");

                // Subscribe to the specified topic
                client.Subscribe(new string[] { topic }, new byte[] { qos });

                // Handle received messages
                client.MqttMsgPublishReceived += Client_MqttMsgPublishReceived;

                Console.WriteLine("Subscribed to topic: " + topic);
                Console.WriteLine("Waiting for messages...");
            }
            else
            {
                Console.WriteLine("Failed to connect to the MQTT server.");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error occurred while connecting: " + ex.Message);
            TryReconnect();
        }
    }

    // Method to disconnect from the MQTT server
    public void Disconnect()
    {
        if (client != null && client.IsConnected)
        {
            try
            {
                // Unsubscribe from the topic
                client.Unsubscribe(new string[] { topic });

                // Disconnect from the MQTT server
                client.Disconnect();
                Console.WriteLine("Disconnected from the MQTT server.");
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error occurred while disconnecting: " + ex.Message);
            }
        }
    }

    // Method to attempt to reconnect to the MQTT server
    private void TryReconnect()
    {
        if (isReconnecting) return;
        isReconnecting = true;

        new Thread(() =>
        {
            while (!client.IsConnected)
            {
                try
                {
                    Console.WriteLine("Trying to reconnect to the MQTT server...");
                    client.Connect(clientId, username, password);
                    if (client.IsConnected)
                    {
                        Console.WriteLine("Reconnected successfully.");
                        // Resubscribe to the topic
                        client.Subscribe(new string[] { topic }, new byte[] { qos });
                        isReconnecting = false;
                        break;
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Reconnection failed: " + ex.Message);
                }
                Thread.Sleep(5000); // Try to reconnect every 5 seconds
            }
        }).Start();
    }

    // Event handler for the connection closed event
    private void Client_ConnectionClosed(object sender, EventArgs e)
    {
        Console.WriteLine("The connection to the MQTT server has been closed.");
        TryReconnect();
    }

    // Event handler for received messages
    private void Client_MqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
    {
        // Process the received message
        string message = System.Text.Encoding.UTF8.GetString(e.Message);
        Console.WriteLine("Received message - Topic: " + e.Topic + ", Message content: " + message);
    }
}

class Program
{
    static void Main()
    {
        // MQTT server address
        string broker = "mqtt.assetscontrols.com";
        // MQTT server port
        int port = 1883;
        // Topic to subscribe to , {accessKey}.need to edit it.
        string topic = "upload/ {accessKey}/+/#";
        // Client ID  any Custom Name
        string clientId = "39440B3BD98045AC99EC2CF93EB15461_consumer01";
        // Username web applicaton  loginuser
        string username = "XXXXX";
        // Password  web applicaton  loginpass -MD532
        string password = "XXXXX";
        // QoS level
        byte qos = 1;

        MqttClientExample mqttClient = new MqttClientExample(broker, port, topic, clientId, username, password, qos);
        mqttClient.Connect();

        Console.WriteLine("Press any key to disconnect...");
        Console.ReadKey();
        mqttClient.Disconnect();
    }
}