C#实现MQTT通讯（c#modbustcp通讯协议实例详解）

一、安装MQTTnet

二、引用dll

using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Protocol;

三、建立MQTT连接

public IMqttClient _mqttClient;
string serverIP, serverPort, user, pwd;


public MqttHelper(string ipAddr, string port, string userName, string userPwd)
{
	serverIP = ipAddr;
	serverPort = port;
	user = userName;
	pwd = userPwd;
}


MqttClientOptions options = null;
public Action<string> GetActionSubscribe;
public async void ConntionServer()
{
	try
	{
		options = new MqttClientOptions() { ClientId = Guid.NewGuid().ToString("D") };
		options.ChannelOptions = new MqttClientTcpOptions()
		{
			Server = serverIP,
			Port = Convert.ToInt32(serverPort)
		};
		options.Credentials = new MqttClientCredentials()
		{
			Username = user,
			Password = pwd
		};
		options.CleanSession = true;
		options.KeepAlivePeriod = TimeSpan.FromSeconds(100.5);
		options.KeepAliveSendInterval = TimeSpan.FromSeconds(20000);


		if (null != _mqttClient)
		{
			await _mqttClient.DisconnectAsync();
			_mqttClient = null;
		}
		
		_mqttClient = new MqttFactory().CreateMqttClient();
		
		//接收信息
		_mqttClient.ApplicationMessageReceived += (sender, args) =>
		{
			GetActionSubscribe?.Invoke(Encoding.UTF8.GetString(args.ApplicationMessage.Payload));
		};


		_mqttClient.Connected += (sender, args) =>
		{


		};


		_mqttClient.Disconnected += (sender, args) =>
		{


		};


		await _mqttClient.ConnectAsync(options);
	}
	catch (Exception ex)
	{


	}
}


public async void DisConntionServer()
{
	try
	{
		if (null != _mqttClient && _mqttClient.IsConnected)
		{
			await _mqttClient.DisconnectAsync();
			_mqttClient.Dispose();
			_mqttClient = null;
		}
	}
	catch (Exception ex)
	{


	}
}


public async void HeartConntionServer()
{
	try
	{
		if (null != _mqttClient && options != null)
		{
			await _mqttClient.ConnectAsync(options);
		}
	}
	catch (Exception ex)
	{


	}
}

四、发布/订阅消息

//发布消息
public void SendMessage(string Topic, string Payload)
{
	try
	{
		Task.Factory.StartNew(async () =>
		{
			var msg = new MqttApplicationMessage()
			{
				Topic = Topic,
				Payload = Encoding.UTF8.GetBytes(Payload),


				QualityOfServiceLevel =
					(MqttQualityOfServiceLevel)
						Enum.Parse(typeof(MqttQualityOfServiceLevel), "1"),
				Retain = false
			};


			if (null != _mqttClient)
			{
				await _mqttClient.PublishAsync(msg);
			}
			else
			{


			}
		});
	}
	catch (Exception ex)
	{
	}
}


//订阅消息
public async void SubscribeAsync(string Topic)
{
	try
	{
		if (_mqttClient == null) return;


		Thread.Sleep(1000);
		await _mqttClient.SubscribeAsync(
		 new List<TopicFilter>
		 {
			new TopicFilter(
				Topic,
				(MqttQualityOfServiceLevel)
					System.Enum.Parse(typeof (MqttQualityOfServiceLevel), "1"))
		 });
	}
	catch (Exception ex)
	{


	}
}

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