C#建立MQTT服务器（基于MQTTnet，局域网）

最近在做一套测量系统，部分用到ESP8266测量上传数据，所以在局域网内首选了MQTT协议来做，主要是方便以后可能会需要拓展到公网服务器做准备。
先来看一下窗体

看一下需要用到的库

应该不用我教大家怎么调入MQTTnet包吧（NuGet包）

下面是具体的内容：

namespace MQTT_STA
{
    public partial class Form1 : Form
    {
        int lianjie = 0;
        public delegate void MyInvoke(string str1, string str2, string str3, string str4);
        public Form1()
        {
            InitializeComponent();
        }



        private void button1_Click(object sender, EventArgs e)
        {
            StartMqttServer();
        }


        public MqttServer mqttServer = null;
        public async void StartMqttServer()
        {
            try
            {
                if (mqttServer == null)
                {
                    var optionsBuilder = new MqttServerOptionsBuilder()
                    .WithDefaultEndpoint().WithDefaultEndpointPort(Convert.ToInt32(textBox1.Text)).WithConnectionValidator(
                        c =>
                        {
                            if (!c.Username.Equals(textBox3.Text.ToString()))
                            {
                                c.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
                                return;
                            }

                            if (!c.Password.Equals(textBox2.Text.ToString()))
                            {
                                c.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
                                return;
                            }

                            c.ReasonCode = MqttConnectReasonCode.Success;
                        }).WithSubscriptionInterceptor(
                        c =>
                        {
                            c.AcceptSubscription = true;
                        }).WithApplicationMessageInterceptor(
                        c =>
                        {
                            c.AcceptPublish = true;
                        });

                    mqttServer = new MqttFactory().CreateMqttServer() as MqttServer;
                    mqttServer.ClientConnectedHandler = new MqttServerClientConnectedHandlerDelegate(OnMqttServerClientConnected);
                    mqttServer.ClientDisconnectedHandler = new MqttServerClientDisconnectedHandlerDelegate(OnMqttServerClientDisconnected);
                    mqttServer.ApplicationMessageReceivedHandler = new MqttApplicationMessageReceivedHandlerDelegate(OnMqttServer_ApplicationMessageReceived);
                    await mqttServer.StartAsync(optionsBuilder.Build());
                    toolStripLabel1.Text = "启动成功！";


                }
            }
            catch (Exception ex)
            {
                toolStripLabel1.Text = "启动失败......";
            }
        }


        public async void StopMqttServer()
        {
            if (mqttServer == null) return;
            try
            {
                await mqttServer?.StopAsync();
                mqttServer = null;
                toolStripLabel1.Text = "关闭成功";
            }
            catch (Exception ex)
            {
                toolStripLabel1.Text = "关闭失败......";
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            ServerPublishMqttTopic();
        }


        public async void ServerPublishMqttTopic()
        {
            await mqttServer.SubscribeAsync(textBox4.Text);
            label5.Text = textBox4.Text+"订阅成功！";
        }

        private void button3_Click(object sender, EventArgs e)
        {
            ServerPublishMqttTopic(textBox6.Text, textBox7.Text);
        }

        public async void ServerPublishMqttTopic(string topic, string payload)
        {
            var message = new MqttApplicationMessage()
            {
                Topic = topic,
                Payload = Encoding.UTF8.GetBytes(payload)
            };
            await mqttServer.PublishAsync(message);
            textBox5.Text = textBox5.Text + "主题："+topic+"\n内容："+payload+"\n发送成功！\n";
        }

        private void toolStripButton1_Click(object sender, EventArgs e)
        {
            StopMqttServer();
        }


        public void OnMqttServerClientConnected(MqttServerClientConnectedEventArgs e)
        {
            lianjie++;
            toolStripLabel2.Text = "连接数：" +lianjie;

        }


        public void OnMqttServerClientDisconnected(MqttServerClientDisconnectedEventArgs e)
        {
            lianjie--;
            toolStripLabel2.Text = "连接数：" + lianjie;

        }

        public void OnMqttServer_ApplicationMessageReceived(MqttApplicationMessageReceivedEventArgs e)
        {

                string text = Encoding.UTF8.GetString(e.ApplicationMessage.Payload);
                string Topic = e.ApplicationMessage.Topic;
                string QoS = e.ApplicationMessage.QualityOfServiceLevel.ToString();
                string Retained = e.ApplicationMessage.Retain.ToString();

                MyInvoke jieshou = new MyInvoke(jieshouo);
                this.BeginInvoke(jieshou, new Object[] { Topic, QoS, Retained, text });
            
        }

        public void jieshouo(string strr1, string strr2, string strr3, string strr4)
        {
            
            textBox5.Text = textBox5.Text +"主题来源："+ strr1 +"\nQoS:"+ strr2+"\nRetained:" + strr3+"\n内容:" + strr4+"\n----\n";
        }

    }
}

响应函数我没有全列出来，大家可以参考
https://blog.csdn.net/xiakexingtx/article/details/108281359
的文章自行添加动作函数
↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓
上面的
mqttServer.ClientConnectedHandler = new MqttServerClientConnectedHandlerDelegate(OnMqttServerClientConnected);
mqttServer.ClientDisconnectedHandler = new MqttServerClientDisconnectedHandlerDelegate(OnMqttServerClientDisconnected);
大家多了解了解eventhandle就没问题了

下面来说一下具体的使用：

客户端具体的接入：
mqtt客户端需要接入的地址一共有四种（我们已经加了三个了，ip是第四个，不需要用户自定）：
ip，端口，账号，密码
-----------------------------------------------------------------------------------------------
ip----
win+r——cmd——ipconfig里面的ipv4地址就是了（如果大家用emqx平台或者腾讯阿里的话请自行搞）

端口----
自行选择

账号----
自行选择

密码----
自行选择
-----------------------------------------------------------------------------------------------
我用来测试的客户端软件是MQTT.fx
目前的缺陷，客户端不能发送空内容，否则服务端程序会报错。

软件的教程百度上一大把我就不说了

好了，大部分都是前人的借鉴，只不过我来整理了一下。