WPF Core—MqttNet開源庫通訊實踐

MqttNet作為.Net平台下的一個基於MQTT通信的開源庫, Github地址: https://github.com/chkr1011/MQTTnet。

本章內容主要介紹MQTT服務器與客戶端之間如何通信, 創建實例等相關內容。

點擊視頻教程

添加MQTT包

- 創建基於NetCore平台的WPF項目,通過NuGet安裝Mqttnet
    1.方式一(Package Manager): Install-Package MQTTnet -Version 3.0.8
    2.方式二(Net CLI[Common Language  Infrastructure]): dotnet add package MQTTnet --version 3.0.8
    3...
    等: 手動方式添加NuGet包, 搜索:MqttNet進行安裝。截止2020-03-25最新版本為3.0.8

創建MQTT服務端:

    IMqttServer server;
    List<UserInstance> instances;
    /// <summary>
        /// 創建MQTT服務端
        /// </summary>
        private async void Init()
        {
            var optionBuilder = new MqttServerOptionsBuilder().
                //設置默認IP: 127.0.0.1 ，端口1883，啟用連接驗證器
                WithDefaultEndpoint().WithDefaultEndpointPort(1883).WithConnectionValidator(
                c =>
                {
                    //此處忽略驗證,做簡單為空驗證處理進行測試
                    var flag = (c.Username != "" && c.Password != "") ? true : false;

                    if (!flag)
                    {
                        //返回錯誤碼
                        c.ReasonCode = MQTTnet.Protocol.MqttConnectReasonCode.BadUserNameOrPassword;
                        return;
                    }
                    //設置代碼為 Success
                    c.ReasonCode = MQTTnet.Protocol.MqttConnectReasonCode.Success;
                    instances.Add(new UserInstance()  //緩存到內存的List集合當中
                    {
                        clientId = c.ClientId,
                        userName = c.Username,
                        passWord = c.Password
                    });
                    Showlog($"{DateTime.Now}:賬號:{c.Username}已訂閱!\r\n");
                }).WithSubscriptionInterceptor(c => 
                {
                    //消息攔截器
                    if (c == null) return;
                    c.AcceptSubscription = true;
                    Showlog($"{DateTime.Now}:訂閱者{c.ClientId}\r\n");
                }).WithApplicationMessageInterceptor(c =>
                {
                    //應用程序消息攔截器
                    if (c == null) return;
                    c.AcceptPublish = true;
                    string str = c.ApplicationMessage?.Payload == null ? null : Encoding.UTF8.GetString(c.ApplicationMessage?.Payload) + "\r\n";
                    Showlog($"{DateTime.Now}:{str}\r\n");
                })

                ;
            //創建MQTT服務端
            server = new MqttFactory().CreateMqttServer();
            //用戶斷開通知
            server.UseClientDisconnectedHandler(c =>
            {
                var use = instances.FirstOrDefault(t => t.clientId == c.ClientId);
                if (use != null)
                {
                    instances.Remove(use);
                    Showlog($"{DateTime.Now}:訂閱者{use.userName}已退出\r\n");
                }
            });
            //啟動服務
            await server.StartAsync(optionBuilder.Build());
        }

- 下代碼為實體類對象, 用於緩存用戶信息

    public class UserInstance
    {
        public string clientId { get; set; }
        public string userName { get; set; }
        public string passWord { get; set; }
    }

- 服務端發送消息至客戶端方法

                server.PublishAsync(new MqttApplicationMessage()
                {
                    Topic = arg.clientId,  //client id
                    QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.ExactlyOnce, //只發送一次
                    Retain = false,
                    Payload = Encoding.UTF8.GetBytes($"{DateTime.Now}:服務器:明天都不要來上班了！")  //測試內容
                }); ;

創建MQTT客戶端

- 定義clienId 用於模擬緩存用戶的clientId,

         IMqttClient client;
         string clientId = "";
          /// <summary>
        /// 啟動MQTT客戶端
        /// </summary>
        private async void Init()
        {
            //模擬唯一ID
            clientId = Guid.NewGuid().ToString();
            //本地TCP連接, 127.0.0.1 端口 1883 , 測試情況下賬號密碼固定 admin  123
            var options = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1", 1883) 
                .WithClientId(clientId).WithCredentials("admin", "123").Build();
            //創建MQTT實例
            client = new MqttFactory().CreateMqttClient();
            //注冊連接成功時間
            client.UseConnectedHandler(async c =>
            {
                //訂閱服務端消息
                await client.SubscribeAsync(new TopicFilterBuilder().WithTopic(clientId).Build());
            }).UseDisconnectedHandler(c => //注冊斷開事件
            {
                Showlog(c.Exception.Message);
            }).UseApplicationMessageReceivedHandler(c => //接受消息事件
            {
                string str = Encoding.UTF8.GetString(c.ApplicationMessage.Payload);
                Showlog(str);
            });
            //啟動客戶端
            await client.ConnectAsync(options);
        }

- 客戶端給服務端發送消息

     var msg = new MqttApplicationMessageBuilder().
                WithTopic(clientId). // client Id
                WithPayload($"{DateTime.Now}:Hello World") //測試消息內容
                .WithExactlyOnceQoS(). //消息模式
                WithRetainFlag().
                Build();;
            client.PublishAsync(msg); //發送消息

        private void Showlog(string str)
        {
            this.Dispatcher.Invoke(() =>
            {
                txtResult.Text += str;
            });
        }

程序運行效果

MqttNet 官方文檔以及介紹

Demo示例 :https://github.com/chkr1011/MQTTnet/wiki
接口文檔: https://github.com/chkr1011/MQTTnet/wiki/Server-and-client-method-documentation