C# mqttnet

以下是使用C#的MQTT.NET库进行MQTT通信的示例程序：

using System;
using System.Text;
using System.Threading;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Options;
using MQTTnet.Extensions.ManagedClient;

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

        var options = new MqttClientOptionsBuilder()
            .WithTcpServer("broker.hivemq.com", 1883) // 设置MQTT服务器地址和端口
            .WithClientId("mqtt_client") // 设置客户端ID
            .Build();

        mqttClient.UseConnectedHandler(async e =>
        {
            Console.WriteLine("Connected to MQTT broker");

            // 订阅主题
            await mqttClient.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic("test/topic").Build());

            // 发布消息
            var message = new MqttApplicationMessageBuilder()
                .WithTopic("test/topic")
                .WithPayload("Hello MQTT")
                .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
                .WithRetainFlag(false)
                .Build();

            await mqttClient.PublishAsync(message);
        });

        mqttClient.UseDisconnectedHandler(async e =>
        {
            Console.WriteLine("Disconnected from MQTT broker");
            await Task.Delay(TimeSpan.FromSeconds(5));

            try
            {
                await mqttClient.ConnectAsync(options);
            }
            catch
            {
                Console.WriteLine("Reconnecting failed");
            }
        });

        await mqttClient.ConnectAsync(options);

        Console.ReadLine();
    }
}

这个示例程序使用了MQTT.NET库来创建一个MQTT客户端，并连接到指定的MQTT服务器。在连接成功后，它订阅了一个名为"test/topic"的主题，并发布了一条消息到该主题。你可以根据需要修改服务器地址、端口、客户端ID、订阅的主题和发布的消息内容。