C# mqtt服务器创建

你好！要在C#中创建MQTT服务器，你可以使用第三方库来帮助你实现。一个流行的选择是使用 Eclipse Paho MQTT C#库。

首先，你需要在你的项目中引用 Paho MQTT C#库。你可以通过NuGet包管理器来安装它，或者手动下载并添加引用。

接下来，你可以按照以下步骤创建一个简单的MQTT服务器：

1. 导入必要的命名空间：

   using System;
   using System.Text;
   using MQTTnet;
   using MQTTnet.Server;

2. 创建一个MQTT服务器实例：

   var mqttServer = new MqttFactory().CreateMqttServer();

3. 配置服务器选项：

   var optionsBuilder = new MqttServerOptionsBuilder()
       .WithDefaultEndpoint()
       .WithDefaultEndpointPort(1883)
       .WithConnectionValidator(context =>
       {
           // 添加自定义验证逻辑，例如用户名密码验证
           if (context.Username != "your_username" || context.Password != "your_password")
           {
               context.ReturnCode = MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
               return;
           }

           context.ReturnCode = MqttConnectReturnCode.ConnectionAccepted;
       });

   mqttServer.Started += (sender, args) =>
   {
       Console.WriteLine("MQTT server started.");
   };

   mqttServer.Stopped += (sender, args) =>
   {
       Console.WriteLine("MQTT server stopped.");
   };

   mqttServer.ClientConnected += (sender, args) =>
   {
       Console.WriteLine($"Client connected: {args.ClientId}");
   };

   mqttServer.ClientDisconnected += (sender, args) =>
   {
       Console.WriteLine($"Client disconnected: {args.ClientId}");
   };

   mqttServer.Started += async (sender, args) =>
   {
       await mqttServer.SubscribeAsync("your_topic");
   };

   mqttServer.UseClientDisconnectedHandler(async e =>
   {
       if (!string.IsNullOrEmpty(e.ClientId))
       {
           Console.WriteLine($"Client disconnected: {e.ClientId}");
       }
       await Task.CompletedTask;
   });

   mqttServer.UseApplicationMessageReceivedHandler(e =>
   {
       Console.WriteLine($"Message received: {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}");
   });

   mqttServer.Started += async (sender, args) =>
   {
       var message = new MqttApplicationMessageBuilder()
           .WithTopic("your_topic")
           .WithPayload("Hello from MQTT server")
           .WithRetainFlag()
           .WithQualityOfServiceLevel(2)
           .Build();

       await mqttServer.PublishAsync(message);
   };

   mqttServer.Started += async (sender, args) =>
   {
       await mqttServer.PublishAsync("your_topic", "Hello from MQTT server");
   };

   var options = optionsBuilder.Build();

4. 启动服务器：

   mqttServer.StartAsync(options).GetAwaiter().GetResult();

这样，你就创建了一个简单的MQTT服务器。你可以根据你的需求进行进一步的配置和处理。记得在程序退出时停止服务器：

mqttServer.StopAsync().GetAwaiter().GetResult();

请注意，这只是一个简单的示例，你可以根据自己的需求进行更复杂的配置和处理。希望对你有所帮助！如有任何问题，请随时提问。