MqttNet 通讯

MQTT,IBM发明的物联网通讯协议基于tcp ip , 收集传感器上的数据。

下图理解：  broker 这里有很多消息，根据主题不同来进行区分，它这里可以保管所有连过来的客户端的数据，然后客户端，通过订阅broker它有的主题进行获取数据。

学习网址：https://github.com/chkr1011/MQTTnet/wiki/Client

broker网址 代理：http://www.mqtt-dashboard.com/

开发(只需客户端)：

vs2015

1.添加引用本文MQTTnet2.8.4（管理NuGet程序包）

2.界面

3.代码

using MQTTnet;
using MQTTnet.Client;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace server
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public static IMqttClient mqttClient = null;
        public static IMqttClientOptions options = null;

        private void Form1_Load(object sender, EventArgs e)
        {
            //实例化对象
            var factory = new MqttFactory();
            mqttClient = factory.CreateMqttClient();
            mqttClient.Connected += SubscribeTopic;
            mqttClient.Disconnected += MqttClient_Disconnected;
            mqttClient.ApplicationMessageReceived += Receive;
            //配置参数
            //options = new MqttClientOptionsBuilder()
            //    .WithClientId(Guid.NewGuid().ToString().Substring(0, 5))
            //    .WithTcpServer("broker.hivemq.com")
            //    .WithCredentials("bud", "%spencer%")
            //    .WithTls()
            //    .WithCleanSession()
            //    .Build();
            options = new MqttClientOptionsBuilder().WithWebSocketServer("broker.hivemq.com:8000/mqtt").Build();
            //连接
            Task.Run(async () => { await ConnectMqtt(); });
        }
        public async Task ConnectMqtt()
        {
            try
            {
                MqttClientConnectResult x = await mqttClient.ConnectAsync(options);
            }
            catch (Exception ex)
            {
                Invoke((new Action(() =>
                {
                    textBox2.Text = $"连接到MQTT服务器失败！" + Environment.NewLine + ex.Message + Environment.NewLine;
                })));
            }
        }
        //接收消息
        public async void Receive(object sender, MqttApplicationMessageReceivedEventArgs e)
        {
            try
            {
                Invoke((new Action(() =>
                {
                    //textBox2.AppendText("### RECEIVED APPLICATION MESSAGE 接收消息 ###");
                    textBox2.AppendText($"Topica(主题) = {e.ApplicationMessage.Topic}" + "\t\n");
                    textBox2.AppendText($"Payloada(内容) = {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}" + "\t\n");
                    //textBox2.AppendText($"+ QoS = {e.ApplicationMessage.QualityOfServiceLevel}");
                    //textBox2.AppendText($"+ Retain = {e.ApplicationMessage.Retain}");
                })));
            }
            catch (Exception ex)
            {
                Invoke((new Action(() =>
                {
                    textBox2.Text = ex.Message;
                })));
            }
        }
        //连接成功
        public async void SubscribeTopic(object sender, EventArgs e)
        {
            Invoke((new Action(() => { label2.Text = "连接成功"; })));
        }

        /// <summary>
        /// 连接失败
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        public async void MqttClient_Disconnected(object sender, EventArgs e)
        {
            Invoke((new Action(() =>
            {
                textBox2.AppendText("连接失败！" + Environment.NewLine);
            })));
            //重新连接
            await Task.Delay(TimeSpan.FromSeconds());
            try
            {
                await mqttClient.ConnectAsync(options);
                Invoke((new Action(() =>
                {
                    textBox2.AppendText("连接成功！");
                })));
            }
            catch
            {
                Invoke((new Action(() =>
                {
                    textBox2.AppendText("连接失败！");
                })));
            }

        }
        /// <summary>
        /// 订阅消息
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            string topic = textBox1.Text;
            mqttClient.SubscribeAsync(new TopicFilterBuilder().WithTopic(topic).Build());
            textBox2.AppendText("### 订阅" + topic + "成功 ###\t\n");
        }

        /// <summary>
        /// 释放资源
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            mqttClient.Dispose();
            textBox2.AppendText("### 断开连接###\t\n");
        }
        /// <summary>
        /// 发布一个主题内容
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button3_Click(object sender, EventArgs e)
        {
            var message = new MqttApplicationMessageBuilder()
                .WithTopic(textBox3.Text)
                .WithPayload(textBox4.Text)
                .WithExactlyOnceQoS()
                .WithRetainFlag()
                .Build();
             mqttClient.PublishAsync(message);
        }
    }
}

4.运行效果

这些数据就是根据你的主题从http://www.mqtt-dashboard.com/   代理取来，你也可以发布主题的内容，别人也可以订阅你的主题，取数据。