使用MQTTnet连接MQTT服务-.NET Framework版本_c# mqttnet 4.3

        上一篇RabbitMQ 搭建MQTT服务  中，创建了admin-test 用户，并创建 test-host 虚拟主机 专门处理MQTT业务，接着我们自己开发一个连接RabbitMQ MQTT服务的客户端

GitHub - harrylsp/MQTTClientContribute to harrylsp/MQTTClient development by creating an account on GitHub.https://github.com/harrylsp/MQTTClient

1.安装MQTTnet库

2. 连接MQTT服务

2.1 创建连接对象

var mqttFactory = new MqttFactory();
mqttClient = mqttFactory.CreateMqttClient() as MqttClient;

2.2 构建连接对象连接参数

var options = new MqttClientOptions
{
	ClientId = clientId,
	ProtocolVersion = MQTTnet.Formatter.MqttProtocolVersion.V311,
	ChannelOptions = new MqttClientTcpOptions
	{
		Server = tcpServer,
		Port = tcpPort
	},
	WillDelayInterval = 10,
	WillMessage = new MqttApplicationMessage
	{
		Topic = $"LastWill/{clientId}",
		Payload = Encoding.UTF8.GetBytes("I Lost the Connection!"),
		QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.ExactlyOnce
	}
};
 
if (options.ChannelOptions == null)
{
	throw new InvalidOperationException();
}
 
if (!string.IsNullOrWhiteSpace(mqttUser))
{
	options.Credentials = new MqttClientCredentials
	{
		Username = mqttUser,
		Password = Encoding.UTF8.GetBytes(mqttPassword)
	};
}
 
// 设置为false，表示创建一个持久会话，在客户端断开连接时，会话仍然保持并保存离线消息，直到会话超时注销。
// 设置为true，表示创建一个新的临时会话，在客户端断开时，会话自动销毁。
options.CleanSession = true;
 
// 连接保活心跳
options.KeepAlivePeriod = TimeSpan.FromSeconds(10);

2.3 注册监听回调事件

mqttClient.ConnectedHandler = new MqttClientConnectedHandlerDelegate(new Action<MqttClientConnectedEventArgs>(e =>
{
	LogManager.WriteLogEx(LOGLEVEL.INFO, "客户端已连接");
}));
 
mqttClient.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(new Action<MqttClientDisconnectedEventArgs>(e =>
{
	LogManager.WriteLogEx(LOGLEVEL.INFO, "客户端已断开连接");
}));
 
mqttClient.ApplicationMessageReceivedHandler = new MqttApplicationMessageReceivedHandlerDelegate(new Action<MqttApplicationMessageReceivedEventArgs>(e =>
{
	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();
 
	LogManager.WriteLogEx(LOGLEVEL.INFO, $"客户端接收消息 >>Topic：{topic}; Qos：{qos}; Retained：{retained}");
	LogManager.WriteLogEx(LOGLEVEL.INFO, $"客户端接收消息 >>Msg：{text}");
}));

2.4 发起连接

await mqttClient.ConnectAsync(options);
LogManager.WriteLogEx(LOGLEVEL.INFO, $"客户端{options.ClientId}尝试连接...");

2.5 连接MQTT服务

3. 订阅主题

await mqttClient.SubscribeAsync(topic);

4. 发布消息

var message = new MqttApplicationMessage
{
	Topic = topic,
	Payload = Encoding.UTF8.GetBytes(payload),
	QualityOfServiceLevel = MQTTnet.Protocol.MqttQualityOfServiceLevel.AtMostOnce,
	Retain = true
};
 
await mqttClient.PublishAsync(message, CancellationToken.None);

5.其他

5.1 MQTT协议介绍

 https://docs.emqx.cn/broker/v4.3/development/protocol.html#mqtt%E5%8D%8F%E8%AE%AE

5.2 源码

GitHub - harrylsp/MQTTClient