C#使用MQTT通讯协议发布订阅主题报文

一、服务端

　　1.添加引用MQTTnet类库　　

　　2.代码：启动一个MQTT服务

 1  　　　　　　 // 启动一个MQTT服务器
 2             // MQTT 
 3             IMqttServer server = new MqttFactory().CreateMqttServer();
 4             server.ClientConnectedHandler = new MqttServerClientConnectedHandlerDelegate(new Action<MqttServerClientConnectedEventArgs>(Connected));
 5 
 6             // IP  Port   用户名  密码
 7             MqttServerOptionsBuilder builder = new MqttServerOptionsBuilder()
 8                 .WithDefaultEndpointBoundIPAddress(System.Net.IPAddress.Parse("127.0.0.1"))// 指定IP
 9                 .WithDefaultEndpointPort(1883)// 默认使用1883端口，换成其他端口可能通信不了
10                 .WithConnectionValidator(valid =>
11                 {
12                     // 用户名和密码验证
13                     if (valid.Username != "admin" && valid.Password != "123456")
14                     {
15                         valid.ReturnCode = MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
16                     }
17                     else
18                         valid.ReturnCode = MqttConnectReturnCode.ConnectionAccepted;
19                 });
20             IMqttServerOptions options = builder.Build();
21             // 启动
22             await server.StartAsync(options);
23 
24             Console.WriteLine("MQTT服务已启动......");
25 
26             // 1、知道有哪个连接进来了
27             // 2、订阅-主题     发布-主题（负载  内容）
28             // 3、服务端接收到一个消息的时候，中转出去（发布的过程：主题进行发布：多个客户端）

 二、客户端

　　1.添加包“MQTTnet.Extensions.ManagedClient”的引用　　

　　2.代码：启动一个MQTT的客户端

 1      // 启动一个MQTT的客户端
 2             IManagedMqttClient mqttClient = new MqttFactory().CreateManagedMqttClient();
 3             // 客户端ID   IP   Port  用户名  密码
 4 
 5             var clientOptions = new MqttClientOptionsBuilder()
 6                 .WithClientId(Guid.NewGuid().ToString())
 7                 .WithTcpServer("127.0.0.1", 1883)
 8                 .WithCredentials("admin", "123456");
 9             var option = new ManagedMqttClientOptionsBuilder()
10                 .WithClientOptions(clientOptions.Build());
11             mqttClient.StartAsync(option.Build()).GetAwaiter().GetResult();
12 
13             // 订阅一个主题 
14             mqttClient.SubscribeAsync(new TopicFilterBuilder().WithTopic("Test").Build());
15             mqttClient.UseApplicationMessageReceivedHandler(msg =>
16             {
17                 Debug.WriteLine(Encoding.UTF8.GetString(msg.ApplicationMessage.Payload));
18             });
19 
20             // 各设备订阅的主题    数据库里维护
21 
22             MqttApplicationMessage msg = new MqttApplicationMessage();
23             msg.Topic = "测试发布";
24             msg.Payload = Encoding.UTF8.GetBytes("客户端发布消息");
25             msg.QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
26             mqttClient.PublishAsync(msg).GetAwaiter().GetResult();