使用NET6实现mqtt

在.NET 6中实现MQTT可以使用第三方库，例如MQTTnet。以下是一个简单的示例，演示如何使用MQTTnet在.NET 6中实现MQTT。

首先，需要安装MQTTnet库。在Visual Studio中，选择项目，右键单击“NuGet Packages”并选择“Manage NuGet Packages”菜单项。在NuGet Package Manager中搜索“MQTTnet”，选择该库并点击“Install”按钮。

然后，在代码中添加以下命名空间：

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

在这个示例中，我们将使用MQTTnet客户端连接到MQTT代理，并发布和订阅MQTT主题。

连接到MQTT代理：

var factory = new MqttFactory();
var client = factory.CreateMqttClient();

var options = new MqttClientOptionsBuilder()
    .WithTcpServer("broker.hivemq.com", 1883) // MQTT代理地址和端口号
    .Build();

await client.ConnectAsync(options);

发布MQTT消息：

var message = new MqttApplicationMessageBuilder()
    .WithTopic("test/topic")
    .WithPayload("Hello World!")
    .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
    .Build();

await client.PublishAsync(message);

订阅MQTT主题：

await client.SubscribeAsync(new TopicFilterBuilder()
    .WithTopic("test/topic")
    .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce)
    .Build());

client.UseApplicationMessageReceivedHandler(e =>
{
    Console.WriteLine($"Received message from topic {e.ApplicationMessage.Topic}: {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}");
});

在这个示例中，我们使用“broker.hivemq.com”作为MQTT代理的地址，端口号为1883。我们发布一个名为“test/topic”的MQTT消息，并订阅相同的主题。当收到来自“test/topic”的MQTT消息时，我们将其打印到控制台。

完整的代码示例：

using System;
using System.Text;
using System.Threading.Tasks;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Options;
using MQTTnet.Protocol;

namespace MqttDemo
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var factory = new MqttFactory();
            var client = factory.CreateMqttClient();

            var options = new MqttClientOptionsBuilder()
                .WithTcpServer("broker.hivemq.com", 1883)
                .Build();

            await client.ConnectAsync(options);

            var message = new MqttApplicationMessageBuilder()
                .WithTopic("test/topic")
                .WithPayload("Hello World!")
                .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
                .Build();

            await client.PublishAsync(message);

            await client.SubscribeAsync(new TopicFilterBuilder()
                .WithTopic("test/topic")
                .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce)
                .Build());

            client.UseApplicationMessageReceivedHandler(e =>
            {
                Console.WriteLine($"Received message from topic {e.ApplicationMessage.Topic}: {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}");
            });

            Console.ReadLine();

            await client.DisconnectAsync();
        }
    }
}