使用MQTTnet搭建MQTT Server

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前言

MQTTnet 是MQTT協議的.NET 開源類庫。

MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server. The implementation is based on the documentation from http://mqtt.org/.

MQTT協議是IBM開發的一個即時通訊協議，有可能成為物聯網的重要組成部分，http://mqtt.org/。

MQTT is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios. It is also ideal for mobile applications because of its small size, low power usage, minimised data packets, and efficient distribution of information to one or many receivers

通過https://github.com/mqtt/mqtt.github.io/wiki/servers 找到官方推薦的服務端軟體,比如：Apache Apollo(ActiveMQ的分支)，通過https://github.com/mqtt/mqtt.github.io/wiki/libraries可以找到推薦的用戶端類庫。

MQTTnet

通過Nuget搜尋MQTT找到了MQTTnet，它不是下載量最多的，也不在官方推薦列表中，主要是因為同時支援用戶端和服務端，所以開始下載試用，結果證明有坑,源碼在vs2015中不能開啟。

開源地址：https://github.com/chkr1011/MQTTnet

首先把官方的控制台程式改成winform的，介面如下：

 public partial class Form1 : Form    {        private MqttServer mqttServer = null;        private MqttClient mqttClient = null;        public Form1()        {            InitializeComponent();        }        private void button_啟動服務端_Click(object sender, EventArgs e)        {            MqttTrace.TraceMessagePublished += MqttTrace_TraceMessagePublished;                    if (this.mqttServer == null)            {                try                {                    var options = new MqttServerOptions                    {                        ConnectionValidator = p =>                        {                            if (p.ClientId == "SpecialClient")                            {                                if (p.Username != "USER" || p.Password != "PASS")                                {                                    return MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;                                }                            }                            return MqttConnectReturnCode.ConnectionAccepted;                        }                    };                    mqttServer = new MqttServerFactory().CreateMqttServer(options);                }                catch (Exception ex)                {                    MessageBox.Show(ex.Message);                    return;                }            }            mqttServer.Start();            this.txt_伺服器.AppendText( $">> 啟動成功..." + Environment.NewLine);        }        private void MqttTrace_TraceMessagePublished(object sender, MqttTraceMessagePublishedEventArgs e)        {            this.Invoke(new Action(() =>            {                this.txt_伺服器.AppendText($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}" + Environment.NewLine);                if (e.Exception != null)                {                    this.txt_伺服器.AppendText( e.Exception + Environment.NewLine);                }            }));        }        private void button_停止服務端_Click(object sender, EventArgs e)        {            if (mqttServer != null)            {                mqttServer.Stop();            }            this.txt_伺服器.AppendText( $">> 停止成功" + Environment.NewLine);        }        private async void button_啟動用戶端_Click(object sender, EventArgs e)        {            if (this.mqttClient == null)            {                var options = new MqttClientOptions                {                    Server = "192.168.2.54",                    ClientId = "zbl",                    CleanSession = true                };                this.mqttClient = new MqttClientFactory().CreateMqttClient(options);                this.mqttClient.ApplicationMessageReceived += MqttClient_ApplicationMessageReceived;                this.mqttClient.Connected += MqttClient_Connected;                this.mqttClient.Disconnected += MqttClient_Disconnected;            }            try            {                await this.mqttClient.ConnectAsync();            }            catch(Exception ex)            {                this.txt_用戶端.AppendText( $"### CONNECTING FAILED ###" + Environment.NewLine);            }        }        private void MqttClient_Connected(object sender, EventArgs e)        {            this.Invoke(new Action( async () =>            {                this.txt_用戶端.AppendText( $"### CONNECTED WITH SERVER ###" + Environment.NewLine);                await this.mqttClient.SubscribeAsync(new List<TopicFilter>{                        new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)                    });                this.txt_用戶端.AppendText($"### SUBSCRIBED  ###" + Environment.NewLine);            }));        }        private void MqttClient_Disconnected(object sender, EventArgs e)        {            this.Invoke(new Action(() =>            {                this.txt_用戶端.AppendText( $"### DISCONNECTED FROM SERVER ###" + Environment.NewLine);            }));        }        private void MqttClient_ApplicationMessageReceived(object sender, MQTTnet.Core.MqttApplicationMessageReceivedEventArgs e)        {            this.Invoke(new Action(() =>            {                this.txt_用戶端.AppendText( $">> Topic:{e.ApplicationMessage.Topic} Payload:{Encoding.UTF8.GetString(e.ApplicationMessage.Payload)} QoS:{e.ApplicationMessage.QualityOfServiceLevel}   Retain:{e.ApplicationMessage.Retain}" + Environment.NewLine);            }));        }        private async void button_停止用戶端_Click(object sender, EventArgs e)        {            if (this.mqttClient != null)            {                await this.mqttClient.DisconnectAsync();            }            this.txt_用戶端.AppendText( $">> 停止成功" + Environment.NewLine);        }        private async void button_發送_Click(object sender, EventArgs e)        {            //var options = new MqttClientOptions            //{            //    Server = "localhost"            //};            //var client = new MqttClientFactory().CreateMqttClient(options);            //await client.ConnectAsync();            var applicationMessage = new MqttApplicationMessage(this.txt_topic.Text,                Encoding.UTF8.GetBytes(this.txt_message.Text), MqttQualityOfServiceLevel.AtMostOnce, false);            await this.mqttClient.PublishAsync(applicationMessage);        }        private void button_清空服務端_Click(object sender, EventArgs e)        {            this.txt_伺服器.Text = "";        }    }

Form1.cs

需要注意的是按照作者說明是

while (true){    Console.ReadLine();    var applicationMessage = new MqttApplicationMessage(        "A/B/C",        Encoding.UTF8.GetBytes("Hello World"),        MqttQualityOfServiceLevel.AtLeastOnce,        false    );    await client.PublishAsync(applicationMessage);}

　用戶端死活都收不到訊息，改成 MqttQualityOfServiceLevel.AtMostOnce 　就可以了，找問題時嘗試下載源碼調試因為vs2015打不開項目也折騰了一會。這個問題提交了issues，期待作者回複。

最後還是建議使用 Apache Apollo，幾篇博文比較有用 MQTT協議的簡單介紹和伺服器的安裝，編寫和MQTT伺服器通訊的Android用戶端程式，參考  【MQTT】在Windows下搭建MQTT伺服器

搭建了MQTT服務端之後需要在Esp8266模組和手機App中分別實現用戶端功能，稍後待續。。。。

 

使用MQTTnet搭建MQTT Server