MQTT

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MQTT is a light weight messaging protocol for sensors that is supported by all major cloud services. See the following cloud provider pages for further details: Azure, AWS and Google Cloud.

The following is a simple example of MQTT:

Tip

Needed NuGets: GHIElectronics.TinyCLR.Networking.Mqtt

var caCertificate = new X509Certificate(UTF8Encoding.UTF8.GetBytes("Your certificate"));

var mqttHost = "your_host";
var mqttPort = 8883; //default 8883
var deviceId = "your_device_id";

var username = "your_username";
var password = "your_password";
var topic = "your_topic";

try {
    var clientSetting = new MqttClientSetting {
        BrokerName = mqttHost,
        BrokerPort = mqttPort,
        ClientCertificate = null,
        CaCertificate = caCertificate,
        SslProtocol = System.Security.Authentication.SslProtocols.Tls12
    };

    var client = new Mqtt(clientSetting);

    var connectSetting = new MqttConnectionSetting {
        ClientId = deviceId,
        UserName = username,
        Password = password
    };

    // Connect to host
    var returnCode = client.Connect(connectSetting);

    var packetId = 1;
                
    // Subscribe to a topic
    client.Subscribe(new string[] { topic }, new QoSLevel[] { QoSLevel.ExactlyOnce },
        (ushort)packetId++);

    // Publish a topic
    client.Publish(topic, Encoding.UTF8.GetBytes("your message"), QoSLevel.MostOnce,
        false, (ushort)packetId);

    // Publish recieved change from a specific topic
    client.PublishReceivedChanged += (object sender, string topic, byte[] data, bool duplicate, QoSLevel qosLevel, bool retain) => {
    Debug.WriteLine("Received message: " + Encoding.UTF8.GetString(data));
    };

}
catch (Exception e) { 
}

Note

The MQTT driver in TinyCLR OS supports client mode only.

The PublishedReceivedChanged Event allows you to select the topic that the device receives the change from.

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Event Handler

The Mqtt driver provides five events:

client.PublishReceivedChanged += (p1, p2, p3, p4, p5, p6) => { Debug.WriteLine("Received message");};
client.PublishedChanged += (a, b, c) => { Debug.WriteLine("Published Changed."); }; ;
client.SubscribedChanged += (a, b, c) => { Debug.WriteLine("Subscribed Changed."); };
client.ConnectedChanged += (a) => { Debug.WriteLine("Connected Changed."); };
client.UnsubscribedChanged += (a, b) => { Debug.WriteLine("Unsubscribed Changed."); };