.Net Core下使用MQTT协议直连IoT平台
【摘要】 .Net平台通过原生MQTT接口，作为南向设备对接OceanConnect平台
因为种种历史原因吧，目前华为平台上对.net的支持案例SDK确实比较少，当看到各种语言的SDK和Demo，唯独缺.net平台的，广大.net开发者也会怀疑.net是不是真的不适合IoT，甚至是互联网。
我的分析是
1、微软从.Net Framework开始所谓的跨平台，仅仅局限在Windows个版本的平台，对其他系统并不支持
2、微软多年以来给人的感觉是闭源，和Linux是死对头，在华为2019HC大会上和一位鲲鹏的工程师聊天也佐证了这一点，他们2019年了还依然对微软是这种认识
一提到开源，一提到互联网、分布式，.net就被轻视，这种态度很常见。
但是，我说的是但是，广大的.neter为什么选择.net平台的，为何mono这么多年都对.net跨平台不懈努力？为什么visual studio被称为宇宙第一的IDE？
那就是生产力。
以前的种种都成为历史了，自从.net core被提出，微软已经是一个亲Linux的代表了，跨平台、高性能已经是核心基础 。且不提Windows IoT, .net core在Linux,Arm上已经非常成熟了，树莓派们的小设备都能轻松玩转。
作为平台也好，工具也好就是为了提高生产力的。再来看看.net对接华为IoT平台，我现在从之前羡慕C/C++,Java,PHP等，在华为的帮助文档中都提供了南向设备的SDK，北向接口的SDK。我也一度怀疑华为为何不提供.net的SDK？没有SDK的帮助，对接将是比其他语言更要复杂，困难要一点点的肯。我也尝试在.net里用[DllImport]特性用c的sdk。
到现在，其实我可以负责任的告诉大家，.net根本不需要华为提供SDK，SDK本身对接口封装后就有不少限制，.net就利用公开的原始接口开发，非常简单和便捷，而且应用起来也灵活。这就是.net的强大生产力，而且.net framework(也可对接桌面程序)和.net core都可以实现。
1、北向接口对接
因为工作关系，对北向接口比较熟悉，华为提供的是restful的接口，和语言无关，实现起来轻车熟路。当时遇到一个困难就是用错了证书密码，现在回头看帮助文档中也说明了用哪个证书和密码，我也专门写过一个帖子来说明北向接口对接。
2、南向设备对接
南向设备比较复杂，对我来说确实是陌生的领域，小熊派这种MCU的板子恐怕只能有C来搞了，借助LiteOS+IoT Studio 也可以胜任。在我的计划中类似小熊派这样的设备甚至是定制更轻巧的，是物联网的常用终端类型。但还有些场景需要配合更丰富的应用，C恐怕做不到(起码需要带个界面啥的我做不到)，或者说做到成本太高，在类似树莓派的独立设备，甚至是在Windows电脑上外接其他设备的场景，.net正是用武之地。
.Net core + Mqttnet 作为南向设备对接华为IoT平台
开发工具：Visual Studio 2019，.Net core 2.2和.net framework 4.7.2
Nuget包：MQTTnet 版本v3.0.8
核心内容三个事件
连接Mqtt服务器：
mqttClient.ConnectAsync(options);订阅服务器Topic
var result = await mqttClient.SubscribeAsync(new TopicFilter()
{
Topic = topicSubscribe,
QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.AtLeastOnce
});服务器发送命令的响应
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, $"{{\"msgType\":\"deviceRsp\",\"mid\":{data.Mid},\"errcode\":0,\"body\":{{\"response\":\"ok\"}}}}");
Console.WriteLine($"设备响应命令:{result.ReasonCode}");
});上报设备多信息到服务器：
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);完整代码如下：
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("连接成功");
});
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, $"{{\"msgType\":\"deviceRsp\",\"mid\":{data.Mid},\"errcode\":0,\"body\":{{\"response\":\"ok\"}}}}");
Console.WriteLine($"设备响应命令:{result.ReasonCode}");
});
mqttClient.UseDisconnectedHandler(handle =>
{
Console.WriteLine($"MQTT 断开连接");
});
}
var utctime = DateTime.UtcNow.ToString("yyyyMMddhh");
var pwd = Encrypt("9e4fbd64f6be2337732a", utctime);
var options = new MqttClientOptionsBuilder()
.WithProtocolVersion(MQTTnet.Formatter.MqttProtocolVersion.V311)
.WithClientId($"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("输入数字 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);
}
}
}
}看这段代码多买的简单，就搞定了整个过程。
我在开发中重新整理了一下，作为一个SDK提供给.net framework和.net core两边使用，封装之后更加简单。完成之后作为nuget包再分享。
作者：神龙居市
