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

 　　　　　　 // 启动一个MQTT服务器
            // MQTT 
            IMqttServer server = new MqttFactory().CreateMqttServer();
            server.ClientConnectedHandler = new MqttServerClientConnectedHandlerDelegate(new Action<MqttServerClientConnectedEventArgs>(Connected));

            // IP  Port   用户名  密码
            MqttServerOptionsBuilder builder = new MqttServerOptionsBuilder()
                .WithDefaultEndpointBoundIPAddress(System.Net.IPAddress.Parse("127.0.0.1"))// 指定IP
                .WithDefaultEndpointPort(1883)// 默认使用1883端口，换成其他端口可能通信不了
                .WithConnectionValidator(valid =>
                {
                    // 用户名和密码验证
                    if (valid.Username != "admin" && valid.Password != "123456")
                    {
                        valid.ReturnCode = MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
                    }
                    else
                        valid.ReturnCode = MqttConnectReturnCode.ConnectionAccepted;
                });
            IMqttServerOptions options = builder.Build();
            // 启动
            await server.StartAsync(options);

            Console.WriteLine("MQTT服务已启动......");

            // 1、知道有哪个连接进来了
            // 2、订阅-主题     发布-主题（负载  内容）
            // 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

     // 启动一个MQTT的客户端
            IManagedMqttClient mqttClient = new MqttFactory().CreateManagedMqttClient();
            // 客户端ID   IP   Port  用户名  密码

            var clientOptions = new MqttClientOptionsBuilder()
                .WithClientId(Guid.NewGuid().ToString())
                .WithTcpServer("127.0.0.1", 1883)
                .WithCredentials("admin", "123456");
            var option = new ManagedMqttClientOptionsBuilder()
                .WithClientOptions(clientOptions.Build());
            mqttClient.StartAsync(option.Build()).GetAwaiter().GetResult();

            // 订阅一个主题 
            mqttClient.SubscribeAsync(new TopicFilterBuilder().WithTopic("Test").Build());
            mqttClient.UseApplicationMessageReceivedHandler(msg =>
            {
                Debug.WriteLine(Encoding.UTF8.GetString(msg.ApplicationMessage.Payload));
            });

            // 各设备订阅的主题    数据库里维护

            MqttApplicationMessage msg = new MqttApplicationMessage();
            msg.Topic = "测试发布";
            msg.Payload = Encoding.UTF8.GetBytes("客户端发布消息");
            msg.QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
            mqttClient.PublishAsync(msg).GetAwaiter().GetResult();