1 . 搭建MQTT服务器

找到上传中的 emqx-5.3.2-windows-amd64 打开bin如下：
链接: emqx-5.3.2-windows-amd64

如果安装失败 在上传中找到链接: VC_redist.x64.exe 安装。
正确后在浏览器输入 http://127.0.0.1:18083 会有如下mqtt服务端管理页面：

进入客户端认证，创建一个服务端池。里面设置用户名密码。



c# 中 mqtt 客户端端口用 ip :1883
websoket 端口用 8083

c# 客户端连接

管理NuGet程序包 添加mqttnet

界面

using MQTTnet;
using MQTTnet.Core;
using MQTTnet.Core.Client;
using MQTTnet.Core.Packets;
using MQTTnet.Core.Protocol;
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 WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private MqttClient mqttClient = null;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {}


        //连接方法
        private async Task ConnectMqttServerAsync()
        {
            if (mqttClient == null)
            {
                mqttClient = new MqttClientFactory().CreateMqttClient() as MqttClient;//创建客户端
                mqttClient.ApplicationMessageReceived += MqttClient_ApplicationMessageReceived;//接收订阅数据
                mqttClient.Connected += MqttClient_Connected;//连接成功后
                mqttClient.Disconnected += MqttClient_Disconnected;//连接不成功
            }

            try
            {
                var options = new MqttClientTcpOptions
                {
                    Server = textBox5.Text,// "172.16.6.133",
                    Port =Convert.ToInt32(textBox7.Text),// 1883,
                    ClientId = Guid.NewGuid().ToString().Substring(0, 5),//这个只要不重复就行
                    UserName = textBox3.Text,// "yado",
                    Password = textBox6.Text // "yado123"
                };
                await mqttClient.ConnectAsync(options);//根据参数连接
            }
            catch (Exception ex)
            {
                Invoke((new Action(() => {
                    txtReceiveMessage.AppendText($"连接到MQTT服务器失败！" + Environment.NewLine + ex.Message + Environment.NewLine);
                })));
            }
        }

        //成功连接回调
        private void MqttClient_Connected(object sender, EventArgs e)
        {
            Invoke((new Action(() => {
                txtReceiveMessage.AppendText("已连接到MQTT服务器！" + Environment.NewLine);
            })));
        }

        //断开回调
        private void MqttClient_Disconnected(object sender, EventArgs e)
        {
            Invoke((new Action(() => {
                txtReceiveMessage.AppendText("已断开MQTT连接！" + Environment.NewLine);
            })));
        }

        //接收到订阅消息
        private void MqttClient_ApplicationMessageReceived(object sender, MqttApplicationMessageReceivedEventArgs e)
        {
            Invoke((new Action(() => {
                txtReceiveMessage.AppendText($">> {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}{Environment.NewLine}");
            })));
        }

        //点击连接
        private void button3_Click(object sender, EventArgs e)
        {
            Task.Run(async () => { await ConnectMqttServerAsync(); });
        }

        //发布主题
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                string topic = textBox1.Text.Trim();
                if (string.IsNullOrEmpty(topic))
                {
                    MessageBox.Show("发布主题不能为空！");
                    return;
                }
                string inputString = textBox2.Text.Trim();
                var appMsg = new MqttApplicationMessage(topic, Encoding.UTF8.GetBytes(inputString), MqttQualityOfServiceLevel.AtMostOnce, false);
                mqttClient.PublishAsync(appMsg);
            }
            catch (Exception ex) {
                MessageBox.Show(ex.Message);
            }
        }
        //订阅
        private void button2_Click(object sender, EventArgs e)
        {
            string topic = textBox4.Text.Trim();

            if (string.IsNullOrEmpty(topic))
            {
                MessageBox.Show("订阅主题不能为空！");
                return;
            }

            if (!mqttClient.IsConnected)
            {
                MessageBox.Show("MQTT客户端尚未连接！");