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1 DLL版本

MQTTnet.DLL版本-2.7.5.0
基于比较老的项目中应用的DLL，其他更高版本变化可能较大，谨慎参考。

2 服务器

开启服务器
关闭服务器
绑定事件【客户端连接服务器事件】
绑定事件【客户端断开(服务器)连接事件】
绑定事件【客户端订阅主题事件】
绑定事件【客户端退订主题事件】
绑定事件【接收客户端(发送)消息事件】

using System;
using System.Net;
using MQTTnet;
using MQTTnet.Server;namespace Demo_MQTT.Model
{public class ServerModel{private static MqttServer _mqttServer = null;private readonly Action<string> _callbackLog;public ServerModel(Action<string> callbackLog){_callbackLog = callbackLog;}/// <summary>/// 绑定客户端连接服务器事件/// </summary>private void MqttServer_ClientConnected(object sender, MqttClientConnectedEventArgs e){WriteLog($"客户端[{e.Client.ClientId}]已连接 {DateTime.Now:yyyy-MM-dd HH:mm:ss}{Environment.NewLine}");}/// <summary>/// 绑定客户端断开连接事件/// </summary>private void MqttServer_ClientDisconnected(object sender, MqttClientDisconnectedEventArgs e){WriteLog($"客户端[{e.Client.ClientId}]已断开连接 {DateTime.Now:yyyy-MM-dd HH:mm:ss}{Environment.NewLine}");}/// <summary>/// 绑定客户端订阅主题事件/// </summary>private void Server_ClientSubscribedTopic(object sensor, MqttClientSubscribedTopicEventArgs e){WriteLog($">>> 客户端{e.ClientId}订阅主题{e.TopicFilter.Topic}");}/// <summary>/// 绑定客户端退订主题事件/// </summary>/// <param name="e"></param>private void Server_ClientUnsubscribedTopic(object sensor, MqttClientUnsubscribedTopicEventArgs e){WriteLog($">>> 客户端{e.ClientId}退订主题{e.TopicFilter}");}/// <summary>/// 绑定接收客户端消息事件/// </summary>private void MqttServer_ApplicationMessageReceived(object sender, MqttApplicationMessageReceivedEventArgs e){WriteLog($"接收到{e.ClientId}发送来的消息！ {DateTime.Now:yyyy-MM-dd HH:mm:ss} {Environment.NewLine}");}private void WriteLog(string log){_callbackLog?.Invoke(log);}/// <summary>/// 开启服务器/// </summary>/// <param name="ip">IP地址</param>/// <param name="port">端口号</param>public void StartServer(string ip, int port){if (_mqttServer == null){var optionsBuilder = new MqttServerOptionsBuilder().WithDefaultEndpointBoundIPAddress(IPAddress.Parse(ip)).WithConnectionBacklog(1000).WithDefaultEndpointPort(port);IMqttServerOptions options = optionsBuilder.Build();try{_mqttServer = new MqttFactory().CreateMqttServer() as MqttServer;_mqttServer.ClientConnected += MqttServer_ClientConnected;_mqttServer.ClientDisconnected += MqttServer_ClientDisconnected;_mqttServer.ApplicationMessageReceived += MqttServer_ApplicationMessageReceived;_mqttServer.ClientSubscribedTopic += Server_ClientSubscribedTopic;_mqttServer.ClientUnsubscribedTopic += Server_ClientUnsubscribedTopic;_mqttServer.StartAsync(options);}catch (Exception ex){Console.WriteLine(ex.Message);return;}WriteLog($"MQTT服务器启动成功 {DateTime.Now:yyyy-MM-dd HH:mm:ss}{Environment.NewLine}");}}/// <summary>/// 关闭服务器/// </summary>public void CloseServer(){_mqttServer?.StopAsync();}}
}

3 客户端

连接服务器
属性：客户端连接状态
客户端断开重连线程
获取所有订阅主题
订阅主题
退订主题
发送消息
绑定事件【客户端连接服务器事件】
绑定事件【客户端断开(服务器)连接事件】
绑定事件【客户端接收消息事件】

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Protocol;namespace Demo_MQTT.Model
{public class ClientModel{/// <summary>/// 记录所有订阅主题，用于断开重连时重新订阅主题/// </summary>private readonly List<string> _subscribeTopics = new List<string>();private MqttClient _mqttClient = null;private string _serverIp;private int _nServerPort;private bool _isRunningReConnectThreadStart = false;private string _clienID;/// <summary>/// 接受消息回调函数，参数：主题，消息内容/// </summary>private readonly Action<string, byte[]> _callbackReceived;private readonly Action<string> _callbackLog;/// <summary>/// 构造函数/// </summary>/// <param name="callbackReceived">接受消息回调函数，参数：主题，消息内容</param>/// <param name="callbackLog"></param>public ClientModel(Action<string, byte[]> callbackReceived, Action<string> callbackLog){_callbackReceived = callbackReceived;_callbackLog = callbackLog;}/// <summary>/// 连接服务器/// </summary>private async void ConnectServer(){try{if (_mqttClient == null){_mqttClient = new MqttFactory().CreateMqttClient() as MqttClient;_mqttClient.Connected += (s, a) => WriteLog($"【{_clienID}】已连接到MQTT服务器!");_mqttClient.Disconnected += (s, a) => WriteLog($"【{_clienID}】已断开MQTT连接!");_mqttClient.ApplicationMessageReceived += (sender, args) =>{_callbackReceived?.Invoke(args.ApplicationMessage.Topic, args.ApplicationMessage.Payload);};}if (_mqttClient.IsConnected) return;IMqttClientOptions options = new MqttClientOptions{ChannelOptions = new MqttClientTcpOptions(){Server = _serverIp,Port = _nServerPort},CleanSession = true};_clienID = options.ClientId;await _mqttClient.ConnectAsync(options);if (_mqttClient.IsConnected){ReConnectThreadStart();SubscribeAsync();}}catch (Exception ex){WriteLog("连接到MQTT服务器失败!");}}/// <summary>/// 客户端重连服务器线程-启动/// </summary>/// <returns></returns>private void ReConnectThreadStart(){if (_isRunningReConnectThreadStart) return;if (_mqttClient != null){new Task(() =>{_isRunningReConnectThreadStart = true;Thread.Sleep(5000);while (true){Thread.Sleep(1000);if (!IsConnect){WriteLog($"客户端[{_clienID}]断开连接，尝试重新连接服务器中...");int i;for (i = 0; i < 60; i++){if (IsConnect) break;WriteLog($"尝试第{i + 1}次连接服务器");ConnectServer();Thread.Sleep(1000);if (IsConnect) break;}_isRunningReConnectThreadStart = i < 60;}if (!_isRunningReConnectThreadStart) break;}}).Start();}}private void WriteLog(string log){_callbackLog?.Invoke(log);}/// <summary>/// 客户端连接状态/// </summary>public bool IsConnect => _mqttClient?.IsConnected == true;/// <summary>/// 连接服务器/// </summary>/// <param name="serverIp">服务器IP</param>/// <param name="serverPort">服务器端口</param>/// <param name="topic"></param>public async void ConnectServer(string serverIp, int serverPort){_serverIp = serverIp;_nServerPort = serverPort;await Task.Run(() => { ConnectServer(); });}/// <summary>/// 关闭客户端，断开客户端和服务器的连接/// </summary>public void CloseClient(){_mqttClient.DisconnectAsync();}/// <summary>/// 发送消息/// </summary>/// <param name="topic">发送主题</param>/// <param name="cmd">发送内容</param>[Obsolete("Obsolete")]public void PublishAsync(string topic, string cmd){var bytes = Encoding.UTF8.GetBytes(cmd);var mode = MqttQualityOfServiceLevel.AtMostOnce;var appMsg = new MqttApplicationMessage(topic, bytes, mode, false);_mqttClient.PublishAsync(appMsg);//发送消息}/// <summary>/// 订阅主题/// </summary>/// <param name="topics">主题标识</param>public void SubscribeAsync(params string[] topics){foreach (var topic in topics){if (!_subscribeTopics.Contains(topic)){_subscribeTopics.Add(topic);}}var topicFilters = _subscribeTopics.Select(topic => new TopicFilter(topic, MqttQualityOfServiceLevel.AtMostOnce)).ToList();_mqttClient?.SubscribeAsync(topicFilters);}/// <summary>/// 退订已订阅主题/// </summary>/// <param name="topics">主题标识</param>public void UnSubscribeAsync(params string[] topics){if (topics == null || topics.Length == 0) return;var topicFilters = topics.Select(topic => new TopicFilter(topic, MqttQualityOfServiceLevel.AtMostOnce)).ToList();_mqttClient.SubscribeAsync(topicFilters);}/// <summary>/// 获取所有订阅主题/// </summary>public string[] GetAllTopic => _subscribeTopics.ToArray();}
}