C#实现MQTT客户端及调试方法

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

// 创建MQTT客户端对象
private IMqttClient mqttClient;

// 创建一些用于显示的变量
private bool mqttIsConnected = false; // 已连接
private string Subscribe_Topic = "Topic"; // 订阅的Topic
private string Subscribe_Payload = ""; // 订阅的内容
private string Subscribe_Time = ""; // 接收时间
private string Subscribe_Qos = "QoS: 0"; // 接收级别

/// <summary>
/// 连接MQTT代理成功事件
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
private Task MqttClient_ConnectedAsync(MqttClientConnectedEventArgs arg)
{
    MessageBox.Show("MQTT客户端连接成功", "MQTT提示");
    mqttIsConnected = true;
    mqttClient.SubscribeAsync(Subscribe_Topic, MqttQualityOfServiceLevel.ExactlyOnce); //Qos2
    return Task.CompletedTask;
}

/// <summary>
/// MQTT连接断开事件
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
private Task MqttClient_DisconnectedAsync(MqttClientDisconnectedEventArgs arg)
{
    MessageBox.Show("MQTT客户端连接已断开", "MQTT提示");
    mqttIsConnected = false;
    return Task.CompletedTask;
}

/// <summary>
/// 订阅主题
/// </summary>
/// <param name="topic"></param>
private async void ClientSubscribeTopic(string topic)
{
    if(mqttIsConnected)
    {
        await mqttClient.SubscribeAsync(topic);
    }
}

/// <summary>
/// 收到订阅消息事件
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
private Task MqttClient_ApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs arg)
{
    byte[] data = arg.ApplicationMessage.PayloadSegment.ToArray();
    Subscribe_Time = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.FFF");
    Subscribe_Topic = "Topic: " + arg.ApplicationMessage.Topic;
    switch (arg.ApplicationMessage.QualityOfServiceLevel)
    {
        case MqttQualityOfServiceLevel.AtMostOnce:
        default:
            Subscribe_Qos = "QoS: 0";
            break;
        case MqttQualityOfServiceLevel.AtLeastOnce:
            Subscribe_Qos = "QoS: 1";
            break;
        case MqttQualityOfServiceLevel.ExactlyOnce:
            Subscribe_Qos = "QoS: 2";
            break;
    }
    Subscribe_Payload = Encoding.UTF8.GetString(data);
    return Task.CompletedTask;
}

// 连接按钮
private void MQTT_Con_btn_Click(object sender, EventArgs e)
{
    try
    {
        mqttIsConnected = false;
        var mqttFactory = new MqttFactory();
        var mqttClientOptions = new MqttClientOptionsBuilder()
            .WithTcpServer(MQTT_IP_input.Text, int.Parse(MQTT_Port_input.Text))
            .WithProtocolVersion(MQTTnet.Formatter.MqttProtocolVersion.V311)
            .WithClientId(MQTT_ID_input.Text)
            .WithCleanSession(false)
            .WithKeepAlivePeriod(TimeSpan.FromSeconds(30))
            .WithCredentials(MQTT_User_input.Text, MQTT_Pass_input.Text)
            .Build();
        mqttClient = mqttFactory.CreateMqttClient();
        mqttClient.DisconnectedAsync += MqttClient_DisconnectedAsync;
        mqttClient.ConnectedAsync += MqttClient_ConnectedAsync;
        mqttClient.ApplicationMessageReceivedAsync += MqttClient_ApplicationMessageReceivedAsync;
        Task task = mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
        task.Wait();
    }
    catch (Exception ex)
    {
        MessageBox.Show(this, ex.Message, "MQTT连接出错", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }
}

// 断开按钮
private async void MQTT_Cut_btn_Click(object sender, EventArgs e)
{
    if (mqttIsConnected)
    {
        try
        {
            await mqttClient.DisconnectAsync();
        }
        catch (Exception ex)
        {
            MessageBox.Show(this, ex.Message, "MQTT连接出错", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
    }
}

// 订阅
private void MQTT_Sub_btn_Click(object sender, EventArgs e)
{
    string topic = MQTT_getTopic_input.Text.ToString();
    if (!string.IsNullOrWhiteSpace(topic))
    {
        ClientSubscribeTopic(topic);
    }
    else
    {
        MQTT_getTopic_input.Text = "请输入Topic";
    }
}

// 发布
private void MQTT_Pub_btn_Click(object sender, EventArgs e)
{
    string payload = MQTT_WMsg_input.Text.ToString();
    string mqttTopic = MQTT_putTopic_input.Text.ToString();
    if (!string.IsNullOrWhiteSpace(payload))
    {
        var applicationMessage = new MqttApplicationMessageBuilder()
            .WithTopic(mqttTopic)
            .WithPayload(payload)
            .Build();
        Task<MqttClientPublishResult> task = mqttClient.PublishAsync(applicationMessage);
        task.Wait();
    }
}

private void MQTT_Status_Timer_Tick(object sender, EventArgs e)
{
    if(mqttIsConnected)
    {
        pictureBox1.Visible = true;
        MQTT_Topic_lbl.Text = Subscribe_Topic;
        MQTT_Qos_lbl.Text = Subscribe_Qos;
        MQTT_Time_lbl.Text = Subscribe_Time;
        MQTT_RMsg_output.Text = Subscribe_Payload;
    }
    else
    {
        pictureBox1.Visible = false;
    }
}