.Net Core下使用MQTT協議直連IoT平台

【摘要】 .Net平台通過原生MQTT接口，作為南向設備對接OceanConnect平台

因為種種歷史原因吧，目前華為平台上對.net的支持案例SDK確實比較少，當看到各種語言的SDK和Demo，唯獨缺.net平台的，廣大.net開發者也會懷疑.net是不是真的不適合IoT，甚至是互聯網。

我的分析是

1、微軟從.Net Framework開始所謂的跨平台，僅僅局限在Windows個版本的平台，對其他系統並不支持

2、微軟多年以來給人的感覺是閉源，和Linux是死對頭，在華為2019HC大會上和一位鯤鵬的工程師聊天也佐證了這一點，他們2019年了還依然對微軟是這種認識

一提到開源，一提到互聯網、分布式，.net就被輕視，這種態度很常見。

但是，我說的是但是，廣大的.neter為什么選擇.net平台的，為何mono這么多年都對.net跨平台不懈努力？為什么visual studio被稱為宇宙第一的IDE？

那就是生產力。

以前的種種都成為歷史了，自從.net core被提出，微軟已經是一個親Linux的代表了，跨平台、高性能已經是核心基礎 。且不提Windows IoT, .net core在Linux,Arm上已經非常成熟了，樹莓派們的小設備都能輕松玩轉。

作為平台也好，工具也好就是為了提高生產力的。再來看看.net對接華為IoT平台，我現在從之前羡慕C/C++,Java,PHP等，在華為的幫助文檔中都提供了南向設備的SDK，北向接口的SDK。我也一度懷疑華為為何不提供.net的SDK？沒有SDK的幫助，對接將是比其他語言更要復雜，困難要一點點的肯。我也嘗試在.net里用[DllImport]特性用c的sdk。

到現在，其實我可以負責任的告訴大家，.net根本不需要華為提供SDK，SDK本身對接口封裝后就有不少限制，.net就利用公開的原始接口開發，非常簡單和便捷，而且應用起來也靈活。這就是.net的強大生產力，而且.net framework(也可對接桌面程序)和.net core都可以實現。

1、北向接口對接

因為工作關系，對北向接口比較熟悉，華為提供的是restful的接口，和語言無關，實現起來輕車熟路。當時遇到一個困難就是用錯了證書密碼，現在回頭看幫助文檔中也說明了用哪個證書和密碼，我也專門寫過一個帖子來說明北向接口對接。

2、南向設備對接

南向設備比較復雜，對我來說確實是陌生的領域，小熊派這種MCU的板子恐怕只能有C來搞了，借助LiteOS+IoT Studio 也可以勝任。在我的計划中類似小熊派這樣的設備甚至是定制更輕巧的，是物聯網的常用終端類型。但還有些場景需要配合更豐富的應用，C恐怕做不到(起碼需要帶個界面啥的我做不到)，或者說做到成本太高，在類似樹莓派的獨立設備，甚至是在Windows電腦上外接其他設備的場景，.net正是用武之地。

.Net core + Mqttnet 作為南向設備對接華為IoT平台

開發工具：Visual Studio 2019，.Net core 2.2和.net framework 4.7.2

Nuget包：MQTTnet 版本v3.0.8

核心內容三個事件

連接Mqtt服務器：

mqttClient.ConnectAsync(options);

訂閱服務器Topic

var result = await mqttClient.SubscribeAsync(new TopicFilter()
{
    Topic = topicSubscribe,
    QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.AtLeastOnce

});

服務器發送命令的響應

mqttClient.UseApplicationMessageReceivedHandler(async handle =>
{
    var payload = Encoding.Default.GetString(handle.ApplicationMessage.Payload);
    var data = JsonConvert.DeserializeObject<ReceivedMessage>(payload);
    Console.WriteLine($"收到MSG：{payload}");
    var result = await mqttClient.PublishAsync(topicPublish, $"{{\"msgType\":\"deviceRsp\",\"mid\":{data.Mid},\"errcode\":0,\"body\":{{\"response\":\"ok\"}}}}");
    Console.WriteLine($"設備響應命令:{result.ReasonCode}");
});

上報設備多信息到服務器：

var msg = new SendMessage
{
	Data = new List<Service>
	{
		 new Service
		 {
			 ServiceData = new Dictionary<string, dynamic> { { "storage", st }, { "usedPercent", 10 }  },
			 ServiceId = "Storage",
			 EventTime = DateTime.UtcNow.ToString("yyyyMMddTHHmmssZ")
		 }
	}
};
var payload = JsonConvert.SerializeObject(msg, new JsonSerializerSettings { ContractResolver = new CamelCasePropertyNamesContractResolver() });
var result = await mqttClient.PublishAsync(topicPublish, payload);

完整代碼如下：

using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Connecting;
using MQTTnet.Client.Options;
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Threading.Tasks;
using System.Linq;
using MQTTnet.Client.Receiving;
using System.Text;
using System.Security.Cryptography.X509Certificates;
using MQTTnet.Client.Subscribing;
using MQTTnet.Extensions.ManagedClient;
using System.Security.Cryptography;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

namespace CampusApp
{
    class Program
    {
        private static IMqttClient mqttClient;
                    
        private static string topicPublish = "/huawei/v1/devices/00b1db5e-5331-4ade-8b62-6c670e6c8d98/data/json";
        private static string topicSubscribe = "/huawei/v1/devices/00b1db5e-5331-4ade-8b62-6c670e6c8d98/command/json";
        private static async Task ConnectMqttServerAsync()
        {
            if (mqttClient == null)
            {
                mqttClient = new MqttFactory().CreateMqttClient();

                mqttClient.UseConnectedHandler(async handle =>
                {
                   
                        var result = await mqttClient.SubscribeAsync(new TopicFilter()
                        {
                            Topic = topicSubscribe,
                            QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.AtLeastOnce

                        });
                        Console.WriteLine("連接成功");
                  
                });
                mqttClient.UseApplicationMessageReceivedHandler(async handle =>
                {
                    
                        var payload = Encoding.Default.GetString(handle.ApplicationMessage.Payload);
                        var data = JsonConvert.DeserializeObject<ReceivedMessage>(payload);
                        Console.WriteLine($"收到MSG：{payload}");
                        var result = await mqttClient.PublishAsync(topicPublish, $"{{\"msgType\":\"deviceRsp\",\"mid\":{data.Mid},\"errcode\":0,\"body\":{{\"response\":\"ok\"}}}}");
                        Console.WriteLine($"設備響應命令:{result.ReasonCode}");
                  

                });
                mqttClient.UseDisconnectedHandler(handle =>
                {
                    Console.WriteLine($"MQTT 斷開連接");
                });
            }
           
			var utctime =  DateTime.UtcNow.ToString("yyyyMMddhh");
			var pwd = Encrypt("9e4fbd64f6be2337732a", utctime);
			var options = new MqttClientOptionsBuilder()
				.WithProtocolVersion(MQTTnet.Formatter.MqttProtocolVersion.V311)
				.WithClientId($"00b1db5e-5331-4ade-8b62-6c670e6c8d98_0_0_{utctime}")
				.WithTcpServer("49.4.93.24", 8883)
				.WithCredentials("00b1db5e-5331-4ade-8b62-6c670e6c8d98", pwd)
				//.WithKeepAlivePeriod(TimeSpan.FromSeconds(10))
				.WithKeepAliveSendInterval(TimeSpan.FromSeconds(3))
				.WithTls(new MqttClientOptionsBuilderTlsParameters()
				{
					AllowUntrustedCertificates = false,
					UseTls = true,
					Certificates = new List<byte[]> { new X509Certificate2("rootcert.pem").Export(X509ContentType.Cert) },
					CertificateValidationCallback = delegate { return true; },
					IgnoreCertificateChainErrors = false,
					IgnoreCertificateRevocatireplaceStrings = false
				})
				.WithCleanSession()
				.Build();
			try
            {
                var result = await mqttClient.ConnectAsync(options);
                Console.WriteLine(result.ResultCode);
            }
            catch (Exception ex)
            {

                Console.WriteLine(ex.Message);
            }
        }
        static string Encrypt(string message, string secret)
        {
            secret = secret ?? "";
            //var encoding = new System.Text.ASCIIEncoding();
            var encoding = new System.Text.UTF8Encoding();
            byte[] keyByte = encoding.GetBytes(secret);
            byte[] messageBytes = encoding.GetBytes(message);
            using (var hmacsha256 = new HMACSHA256(keyByte))
            {
                byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
                //return Convert.ToBase64String(hashmessage);
                StringBuilder rst = new StringBuilder();
                for (int i = 0; i < hashmessage.Length; i++)
                {
                    rst.Append(hashmessage[i].ToString("x2"));
                }
                return rst.ToString();
            }
        }
        static async Task Main(string[] args)
        {
            try
            {
                _ = Task.Run(async () =>
                {
                    await ConnectMqttServerAsync();
                });

                while (mqttClient?.IsConnected != true)
                {
                    await Task.Delay(1000);
                }

                while (true)
                {
                    Console.WriteLine("輸入數字 storage：");
                    var input = Console.ReadLine();
                    if (!int.TryParse(input, out int st))
                        continue;

                    var msg = new SendMessage
                    {
                        Data = new List<Service>
                        {
                             new Service
                             {
                                 ServiceData = new Dictionary<string, dynamic> { { "storage", st }, { "usedPercent", 10 }  },
                                 ServiceId = "Storage",
                                 EventTime = DateTime.UtcNow.ToString("yyyyMMddTHHmmssZ")
                             }
                        }
                    };
                    var payload = JsonConvert.SerializeObject(msg, new JsonSerializerSettings { ContractResolver = new CamelCasePropertyNamesContractResolver() });
                    var result = await mqttClient.PublishAsync(topicPublish, payload);
                    Console.WriteLine($"Publish Result: {result.ReasonCode}");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message + ex.StackTrace);
            }
        }
    }
}

看這段代碼多買的簡單，就搞定了整個過程。

我在開發中重新整理了一下，作為一個SDK提供給.net framework和.net core兩邊使用，封裝之后更加簡單。完成之后作為nuget包再分享。 

作者：神龍居市