MQTTnet for Azure IoT Hub Apps

About

Send Telemetry to an Azure IoT Hub using MQTTnet API. Also send CD Messages as well.

• .Net Core 3.1 Console Works
• • Autogenerates SasToken from Secrets.cs (Device Primary Key) and uses that
• GenerateSas Works
  • Generate SasToken, as per Console app, and copies to clipbaord for Medow app.
• Meadow app. Works
  • Now using Meadow.MQTTnet Nuget package rather than MQTTnet package..
  • Does not use MQTTnet.Extensions.ManagedClient (as does Console app) as not supported.
  • SasTokens generated here don't connect. So paste token from GenerateSas app in Secrets.cs

Nb: Cloud to Device Messages are implmented including Message Properties. But Direct Methods are not implemented.
Also, no Modelling/Twinning implemented.

Monitoring

Suggest using Azure IoT Explorer to monitor telemetry and to send CD messages. About Azure IoT Explorer

Links

• Blog about Meadow Project Lab
• https://github.com/dotnet/MQTTnet (MQTTnet repository)
• Communicate with an IoT hub using the MQTT protocol
• https://dev.to/eduardojuliao/basic-mqtt-with-c-1f88 (Console Code was derived from this)
• Meadow Apps Start here: djaus2/Meadow.ProjectLab.Extensions

Update

Now includes method to generate Sas Token from Device Primary Key.
Fails on Meadow so for that use GenerateSas or Powershell script (as below) on AzCli to get fixed value.

Sample Secrets.cs

using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Globalization;
using System.IO;
using System.Net.Sockets  

using System.Text;

namespace MeadowApplication3
{

    public static class Secrets
    {
        /* Run GenerateSas first which provides a SasToken on the ClipBoard, so paste here then.      
         Alternative: Powershell Command to get SAS Token
         az iot hub generate-sas-token --hub-name HUBNAME --device-id DEVICEID --resource-group AZURERESOURCEGROUP --login IOTHUBCONNECTIONSTRING
         Also -du optional parameter for duration: Valid token duration in seconds.  Default: 3600, 1 hr
       */
        public static bool useThisSasToken = true;
        public static string SasToken = "";
        public static bool UseMQTTnetAPI = true; 
        public static int TelemetryPeriod = 3333;
        public static string WIFI_NAME = "";
        public static string WIFI_PASSWORD = "";

        public static string IOT_CONFIG_IOTHUB_FQDN = "HUBNAME.azure-devices.net";

        public static string DeviceId = "";
        public static string HubName = "";
        public static string DevicePrimaryKey = ""; 
        public static int MqttPort = 8883;

        //INFO https://learn.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-c2d
        public static string subTopic = "devices/+/messages/devicebound/#";

        //INFO https://learn.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-d2c
        public static string pubTopic = $"\"devices/{DeviceId}/messages/events/\"";

        public static string methodTopic =$"\"$iothub/methods/POST/#\"";
  }
}