Azure MQTT

MqttEventGridClient.cs

using System.Security.Cryptography.X509Certificates;
using MQTTnet;
using MQTTnet.Client;

const string eventGridUrl = "<resource>.ts.eventgrid.azure.net";
const string deviceId = "test-device-01";

const string clientCertFile = "test-device-01.crt";
const string clientKetFile = "test-device-01.key";

var cert = X509Certificate2.CreateFromPemFile(clientCertFile, clientKetFile);

var mqttFactory = new MqttFactory();

using var mqttClient = mqttFactory.CreateMqttClient();
var mqttClientOptions = new MqttClientOptionsBuilder()
    .WithTcpServer(eventGridUrl, 8883)
    .WithTlsOptions(o => o.WithClientCertificates(new []
    {
        cert
    }))
    .WithClientId(deviceId)
    .WithCredentials(deviceId)
    .Build();

using var timeout = new CancellationTokenSource(5000);
await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);

Console.WriteLine("The MQTT client is connected.");

await mqttClient.DisconnectAsync();

MqttIotHubClient.cs

using System.Globalization;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using MQTTnet;
using MQTTnet.Client;

const string iotHubUri = "<hub>.azure-devices.net";
const string deviceId = "<id>";
const string accessKey = "<key>";

var username = $"{iotHubUri}/{deviceId}/?api-version=2021-04-12";
var password = GenerateSasToken($"{iotHubUri}/devices/{deviceId}", accessKey);

var mqttFactory = new MqttFactory();

using var mqttClient = mqttFactory.CreateMqttClient();
var mqttClientOptions = new MqttClientOptionsBuilder()
    .WithTcpServer(iotHubUri, 8883)
    .WithTlsOptions(o => o.UseTls())
    .WithClientId(deviceId)
    .WithCredentials(username, password)
    .Build();

using var timeout = new CancellationTokenSource(5000);
await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);

Console.WriteLine("The MQTT client is connected.");

await mqttClient.DisconnectAsync();

return;

static string GenerateSasToken(string resourceUri, string key, string? policyName = null, int expiryInSeconds = 3600)
{
    var fromEpochStart = DateTime.UtcNow - new DateTime(1970, 1, 1);
    var expiry = Convert.ToString((int)fromEpochStart.TotalSeconds + expiryInSeconds);

    var stringToSign = WebUtility.UrlEncode(resourceUri) + "\n" + expiry;

    var hmac = new HMACSHA256(Convert.FromBase64String(key));
    var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));

    var token = string.Format(CultureInfo.InvariantCulture, "SharedAccessSignature sr={0}&sig={1}&se={2}",
        WebUtility.UrlEncode(resourceUri), WebUtility.UrlEncode(signature), expiry);

    if (!string.IsNullOrEmpty(policyName))
    {
        token += "&skn=" + policyName;
    }

    return token;
}