How to determine if the data has been successfully uploaded in C# using MQTT?

In C#, you can use an MQTT client library to upload data and determine success by subscribing to relevant topics.

Firstly, you need to install an MQTT client library using the NuGet package manager, such as MQTTnet.

Afterwards, you can use the following code to upload the data and check if it was successful.

using System;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Client.Options;

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

        var options = new MqttClientOptionsBuilder()
            .WithTcpServer("localhost", 1883) // 设置MQTT服务器的地址和端口
            .Build();

        await client.ConnectAsync(options); // 连接到MQTT服务器

        var message = new MqttApplicationMessageBuilder()
            .WithTopic("topic") // 设置上传数据的主题
            .WithPayload("data") // 设置要上传的数据
            .WithExactlyOnceQoS() // 设置QoS为ExactlyOnce
            .WithRetainFlag() // 设置Retain标志
            .Build();

        var result = await client.PublishAsync(message); // 上传数据

        if (result.ReasonCode == MqttClientPublishReasonCode.Success)
        {
            Console.WriteLine("数据上传成功");
        }
        else
        {
            Console.WriteLine("数据上传失败");
        }

        await client.DisconnectAsync(); // 断开与MQTT服务器的连接
    }
}

In the above code, an MQTT client instance is first created and the address and port of the MQTT server are set using MqttClientOptionsBuilder. Then, the ConnectAsync method is used to connect to the MQTT server.

Next, a message for uploading data was created using MqttApplicationMessageBuilder, where the topic, data, QoS, and Retain flag were set.

Then, upload the data using the PublishAsync method and determine if the upload was successful by checking the ReasonCode property in the returned MqttClientPublishResult object.

Lastly, use the DisconnectAsync method to disconnect from the MQTT server.