MQTTnet3.0.5学习笔记C#的ThreadStart和Thread

OStack程序员社区-中国程序员成长平台 › 门户 › 编程› Node.js›Node.js教程

原作者: [db:作者] 来自: [db:来源] 收藏邀请

段时间在使用MQTTnet，都说这个东西比较好,可是翻了翻网上没有例子给参考一下。

今天算是找到了，给高手的帖子做个宣传吧.

原网址如下：https://blog.csdn.net/chenlu5201314/article/details/94740765

由于GitHub上介绍的东西比较少，以我的水平真是不知道怎么用，先照葫芦画瓢，再看看怎么回事吧：

功能：

把订阅与发布做成一个类，还带有自动重连的功能

using System.Threading;　　　　
using System.Threading.Tasks;
using MQTTnet;　　　　　　　　　　
using MQTTnet.Client;　　　　　　//客户端需要用到
using MQTTnet.Client.Options;  //具体连接时需要用到的属性,ID的名称,要连接Server的名称,接入时用到的账号和密码,掉线时是否重新清除原有名称,还有许多...
using MQTTnet.Packets;　　　　//这个没用上
using MQTTnet.Protocol;　　  //这个也没用上
using MQTTnet.Client.Receiving;　　　　//接收
using MQTTnet.Client.Disconnecting;　　//断线
using MQTTnet.Client.Connecting;　　　　//连接

新建一个类：先写一下变量和一些字段

class HOSMQTT   
{        
private static MqttClient mqttClient = null;        
private static IMqttClientOptions options = null;        
private static bool runState = false;        
private static bool running = false;        
 /// <summary>        
/// 服务器IP        
/// </summary>        
private static string ServerUrl = "182.61.51.85";        
/// <summary>        
/// 服务器端口        
/// </summary>        
private static int Port = 61613;        
/// <summary>        
/// 选项 - 开启登录 - 密码        
/// </summary>        
private static string Password = "ruichi8888";        
/// <summary>        
/// 选项 - 开启登录 - 用户名        
/// </summary>        
private static string UserId = "admin";        
/// <summary>        
/// 主题        
/// <para>China/Hunan/Yiyang/Nanxian</para>        
/// <para>Hotel/Room01/Tv</para>        
/// <para>Hospital/Dept01/Room001/Bed001</para>        
/// <para>Hospital/#</para>        
/// </summary>        
private static string Topic = "China/Hunan/Yiyang/Nanxian";        
/// <summary>        
/// 保留        
/// </summary>        
private static bool Retained = false;       
 /// <summary>       
 /// 服务质量        
/// <para>0 - 至多一次</para>        
/// <para>1 - 至少一次</para>        
/// <para>2 - 刚好一次</para>        
/// </summary>        
private static int QualityOfServiceLevel = 0;
}

先看一下Start方法

public static void Start()
        {
            try
            {
                runState = true;
                Thread thread = new Thread(Work);　　　　//原帖中是这样写的 Thread thread = new Thread(new ThreadStart( Work));
                thread.IsBackground = true;
                thread.Start();
            }
            catch (Exception ex)
            {
                Console.WriteLine( "启动客户端出现问题:" + ex.ToString());
            }
        }

没进入正题之前，先普及一下基本知识

具体请看下面的连接

https://www.cnblogs.com/rosesmall/p/8358348.html

进入整体，介绍连接方法 Work

private static void Work()
        {
            running = true;
            Console.WriteLine("Work >>Begin");
            try
            {
                var factory = new MqttFactory();　　　　　　　　//声明一个MQTT客户端的标准步骤 的第一步
                mqttClient = factory.CreateMqttClient() as MqttClient;  //factory.CreateMqttClient()实际是一个接口类型（IMqttClient）,这里是把他的类型变了一下
                options = new MqttClientOptionsBuilder()　　　　//实例化一个MqttClientOptionsBulider
                    .WithTcpServer(ServerUrl, Port)
                    .WithCredentials(UserId, Password)
                    .WithClientId("XMan")
                    .Build();　　　　　　　　　　　　　　　　　　
                mqttClient.ConnectAsync(options);　　　　　　//连接服务器
　　　　　　　　
　　　　　　　　　　//下面这些东西是什么，为什么要这么写，直到刚才我还是不懂，不过在GitHub的网址我发现了出处.
                mqttClient.ConnectedHandler = new MqttClientConnectedHandlerDelegate(new Func<MqttClientConnectedEventArgs, Task>(Connected));
                mqttClient.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(new Func<MqttClientDisconnectedEventArgs, Task>(Disconnected));
                mqttClient.ApplicationMessageReceivedHandler = new MqttApplicationMessageReceivedHandlerDelegate(new Action<MqttApplicationMessageReceivedEventArgs>(MqttApplicationMessageReceived));
                while (runState)
                {

                    Thread.Sleep(100);

                }
            }
            catch(Exception exp)
            {

                Console.WriteLine(exp);
            }
            Console.WriteLine("Work >>End");

            running = false;

            runState = false;
        }

先来看看MqttClient 类里面都有什么东西

需要实现的接口，如何实现，说重点！

在GitHub上有个地方进去看看就知道了‘

这个页面的最下方写着如何实现 https://github.com/chkr1011/MQTTnet/wiki/Upgrading-guide

private void Something()
{
    mqttClient.ApplicationMessageReceivedHandler = new MqttApplicationMessageReceivedHandlerDelegate(OnAppMessage);
    mqttClient.ConnectedHandler = new MqttClientConnectedHandlerDelegate(OnConnected);
    mqttClient.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(OnDisconnected);
}

private async void OnAppMessage(MqttApplicationMessageReceivedEventArgs e)
{
}

private async void OnConnected(MqttClientConnectedEventArgs e)
{
}

private async void OnDisconnected(MqttClientDisconnectedEventArgs e)
{
}

在开始Connected方法之前有必要看一下关于同步和异步的知识，

现学现卖简单说一下：

Task就是异步的调用，就在不影响主线程运行的另一个线程，但是他能像线程池一样更高效的利用现有的空闲线程

async必须用来修饰Task ,void，或者Task<TResult>, await是等待异步线程Task.Run()开始的后台线程执行完毕。

记住要是Task 实现异步功能，必须用 async 修饰，且async 与await成对出现。

详见下面大神写的大作:https://www.cnblogs.com/doforfuture/p/6293926.html

下面是什么意思？

mqttClient.ConnectedHandler = new MqttClientConnectedHandlerDelegate(new Func<MqttClientConnectedEventArgs, Task>(Connected));

MqttClientConnectedHandlerDelegate 这个实例实现了mqttClient.ConnectedHandler接口

new Func<MqttClientConnectedEventArgs, Task>(Connected) ，

使用Func委托传入MqttClientConnectedEventArgs类型的参数，返回的类型是Task,Task是一个类，这个类没有返回值，如果有返回值就是Task<TResult>。

是委托就要带一个方法取实现，这个方法就是Connected。

这句话的意思是，用MqttClientConnectedHandlerDelegate实现接口，同时使用委托取调用Connected的方法，并且给这个方法传入一个MqttClientConnectedEventArgs参数，

这个委托的返回值是Task（就是不需要返回类型的异步调用），这也就定义了Connected的类型必须是async Task。

好了来看下 Connected，这个函数什么意思

就是与服务器连接之后要干什么，订阅一个Topic，或几个Topic。连接之前已经连接了Connectasync(),如果断线还会重连，后面会提到。

这个就连接之后需要做的事----订阅！

        private static async Task Connected(MqttClientConnectedEventArgs e)
        {
            try
            {
                List<TopicFilter> listTopic = new List<TopicFilter>();
                if (listTopic.Count() <= 0)
                {
                    var topicFilterBulder = new TopicFilterBuilder().WithTopic(Topic).Build();
                    listTopic.Add(topicFilterBulder);
                    Console.WriteLine("Connected >>Subscribe " + Topic);
                }                await mqttClient.SubscribeAsync(listTopic.ToArray());
                Console.WriteLine("Connected >>Subscribe Success");
            }
            catch (Exception exp)
            {
                Console.WriteLine(exp.Message);
            }
        }

TopicFilter是一个Topic详细信息的类

掉线的发生时会执行这个函数

private static async Task Disconnected(MqttClientDisconnectedEventArgs e)
        {
            try
            {
                Console.WriteLine("Disconnected >>Disconnected Server");
                await Task.Delay(TimeSpan.FromSeconds(5));
                try
                {
                    await mqttClient.ConnectAsync(options);
                }
                catch (Exception exp)
                {
                    Console.WriteLine("Disconnected >>Exception " + exp.Message);
                }
            }
            catch (Exception exp)
            {
                Console.WriteLine(exp.Message);
            }
        }

越写问题越多，这个为什么断线的时候会执行这个方法，这不是事件，只是接口！

怎么实现的？看了一下源码，一时只看了大概，这些功能的绑定都是在ConnectAsync的时候就完成了！

下面接收到消息的时候

        /// <summary>
        /// 接收消息触发事件
        /// </summary>
        /// <param name="e"></param>
        private static void MqttApplicationMessageReceived(MqttApplicationMessageReceivedEventArgs e)
        {
            try
            {
                string text = Encoding.UTF8.GetString(e.ApplicationMessage.Payload);
                string Topic = e.ApplicationMessage.Topic; string QoS = e.ApplicationMessage.QualityOfServiceLevel.ToString();
                string Retained = e.ApplicationMessage.Retain.ToString();
                Console.WriteLine("MessageReceived >>Topic:" + Topic + "; QoS: " + QoS + "; Retained: " + Retained + ";");
                Console.WriteLine("MessageReceived >>Msg: " + text);
            }
            catch (Exception exp)
            {
                Console.WriteLine(exp.Message);
            }
        }

最后就是发布：一般会选择0，如果选择其他的情况在订阅端不在的时候，服务器可能会崩溃

/// <summary>       
        /// /// 发布        
        /// <paramref name="QoS"/>        
        /// <para>0 - 最多一次</para>        
        /// <para>1 - 至少一次</para>        
        /// <para>2 - 仅一次</para>        
        /// </summary>       
        /// <param name="Topic">发布主题</param>        
        /// <param name="Message">发布内容</param>        
        /// <returns></returns>        
        public static void Publish( string Topic,string Message)
        {
            try
            {
                if (mqttClient == null)
                    return;
                if (mqttClient.IsConnected == false)
                    mqttClient.ConnectAsync(options);
                if (mqttClient.IsConnected == false)
                {
                    Console.WriteLine("Publish >>Connected Failed! ");
                    return;
                }
                Console.WriteLine("Publish >>Topic: " + Topic + "; QoS: " + QualityOfServiceLevel + "; Retained: " + Retained + ";");
                Console.WriteLine("Publish >>Message: " + Message);
                MqttApplicationMessageBuilder mamb = new MqttApplicationMessageBuilder()                 
                    .WithTopic(Topic)                 
                    .WithPayload(Message).WithRetainFlag(Retained);
                if (QualityOfServiceLevel == 0)
                {
                    mamb = mamb.WithAtMostOnceQoS();
                }
                else if (QualityOfServiceLevel == 1)
                {
                    mamb = mamb.WithAtLeastOnceQoS();
                }
                else if (QualityOfServiceLevel == 2)
                {
                    mamb = mamb.WithExactlyOnceQoS();
                }
                mqttClient.PublishAsync(mamb.Build());
            }
            catch (Exception exp)
            {
                Console.WriteLine("Publish >>" + exp.Message);
            }
        }