基於.net C# Socket WinForm MQTT 客戶端開發

 

1、什麼是MQTT？
　　MQTT（Message Queuing Telemetry Transport，消息隊列遙測傳輸協議），是一種基於發佈/訂閱（publish/subscribe）模式的"輕量級"通訊協議，該協議構建於TCP/IP協議上，由IBM在1999年發佈。MQTT最大優點在於，可以以極少的代碼和有限的帶寬，爲連接遠程設備提供實時可靠的消息服務。作爲一種低開銷、低帶寬佔用的即時通訊協議，使其在物聯網、小型設備、移動應用等方面有較廣泛的應用。

　　MQTT是一個基於客戶端-服務器的消息發佈/訂閱傳輸協議。MQTT協議是輕量、簡單、開放和易於實現的，這些特點使它適用範圍非常廣泛。在很多情況下，包括受限的環境中，如：機器與機器（M2M）通信和物聯網（IoT）。其在，通過衛星鏈路通信傳感器、偶爾撥號的醫療設備、智能家居、及一些小型化設備中已廣泛使用。
（具體描述自行百度）

 

　　本文將基於.Net C# Socket WinForm MQTT 客戶端開發，實現服務端連接，消息發佈，消息訂閱，取消訂閱及接收服務端返回消息功能。

 

 

2、連接服務端

　　客戶端連接服務端，啓動異步接收服務端消息。

 1                     //連接選項
 2                     var option = new MQTT.MQTTClientOption()
 3                     {
 4                         ClientId = this.txtClientId.Text,
 5                         IpString = this.txtServer.Text,
 6                         Port = Convert.ToInt32(this.txtPort.Text),
 7                         UserName = this.txtUserName.Text,
 8                         Password = this.txtPassword.Text
 9                     };
10                     //實例客戶端
11                     this.mqttClient = new MQTT.MQTTClient();
12                     this.mqttClient.ClientReceived += MqttClient_ClientReceived;
13                     var result = await this.mqttClient.ConnectAsync(option);
14                     if(result.State == false)
15                     {
16                         MessageBox.Show(result.Fail, "提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
17                         return;
18                     }
19                     //開始接收
20                     this.mqttClient.BeginReceive();

3、發佈消息

　　客戶端向服務端發送消息，主要包括主題，內容及消息質量。

　　發送消息程序

 1         private short _PacketId = 1;
 2         private async void BtnPublish_Click(object sender, EventArgs e)
 3         {
 4             this.btnPublish.Enabled = false;
 5             this.Cursor = Cursors.WaitCursor;
 6             try
 7             {
 8                 short qos = 0;
 9                 if (rdbLevel1.Checked)
10                     qos = 1;
11                 if (rdbLevel2.Checked)
12                     qos = 2;
13                 
14                 var data = new MQTT.PublishEntity()
15                 {
16                     Topic = this.txtTopic.Text,
17                     Reload = System.Text.Encoding.UTF8.GetBytes(this.txtContent.Text),
18                     Qos = qos,
19                     PacketId=_PacketId
20                 };
21                 var result = await this.mqttClient.PublishAsync(data,false);
22                 if(result.State == false)
23                 {
24                     this.AppendText("發送失敗：" + result.Fail);
25                     return;
26                 }
27                 this._PacketId++;
28                 this.AppendText("發送成功，返回結果：" + result.Result);
29             }
30             finally
31             {
32                 this.btnPublish.Enabled = true;
33                 this.Cursor = Cursors.Default;
34             }
35         }

 

4、訂閱消息

　　客戶端訂閱消息，主要包括過濾主題及消息質量。

　　訂閱消息方法：

 1 private async void BtnSubscribe_Click(object sender, EventArgs e)
 2         {
 3             this.btnSubscribe.Enabled = false;
 4             this.Cursor = Cursors.WaitCursor;
 5            
 6             try
 7             {
 8                 string fail = string.Empty;
 9 
10                 short qos = 0;
11                 if (rdbQos1.Checked)
12                     qos = 1;
13                 if (rdbQos2.Checked)
14                     qos = 2;
15 
16                 MQTT.SubscribeEntity entity = new MQTT.SubscribeEntity();
17                 entity.Filter = this.txtFilter.Text;
18                 entity.Qos = qos;
19 
20                 this.AppendText("開始訂閱...");
21                 //if (mqttClient.Subscribe(this.txtFilter.Text, qos, out result, out fail) == false)
22                 //{
23                 //    this.AppendText(fail);
24                 //    return;
25                 //}
26                 var result = await mqttClient.SubscribeAsync(entity.Filter,entity.Qos);
27                 if (result.State == false)
28                 {
29                     this.AppendText(result.Fail);
30                     return;
31                 }
32                
33                 this.AppendText("訂閱成功！返回結果：" + result.Result);
34                 MQTT.SubscribeHelper.Save(entity);
35 
36                 DataRow drData = this.dtSubscribes.NewRow();
37                 drData["Id"] = entity.Id;
38                 drData["Filter"] = entity.Filter;
39                 drData["Qos"] = entity.Qos;
40                 drData["Count"] = 0;
41                 dtSubscribes.Rows.Add(drData);
42             }
43             finally
44             {
45                 this.btnSubscribe.Enabled = true;
46                 this.Cursor = Cursors.Default;
47             }
48         }

 

5、取消訂閱

　　客戶端取消某一訂閱消息。雙擊訂閱消息行，取消訂閱消息。

 

　　取消訂閱方法：

 1         private async void DataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
 2         {
 3             if (this.dataGridView1.CurrentCell == null)
 4                 return;
 5 
 6             DataRowView drv = this.dataGridView1.CurrentRow.DataBoundItem as DataRowView;
 7             if (drv == null)
 8                 return;
 9 
10             if (MessageBox.Show("確認取消當前選擇：" + drv["Filter"].ToString() + " 訂閱?", "確認", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
11                 return;
12             try
13             {
14                 this.AppendText("開始取消訂閱...");
15                 var result = await mqttClient.UnSubscribeAsync(drv["Filter"].ToString());
16                 if (result.State == false)
17                 {
18                     this.AppendText(result.Fail);
19                     return;
20                 }
21                 this.AppendText("取消訂閱成功！返回結果：" + result.Result);
22                 MQTT.SubscribeHelper.Delete(drv["Id"].ToString());
23                 this.dataGridView1.Rows.RemoveAt(this.dataGridView1.CurrentCell.RowIndex);
24             }
25             catch (Exception ex)
26             {
27                 this.AppendText("取消訂閱異常：" + ex.ToString());
28             }
29 
30         }

 

6、接收服務端消息

　　客戶端接收服務端轉發過來的消息。

 

1         private void MqttClient_ClientReceived(MQTT.MQTTClient client, MQTT.ReceiveResult receive)
2         {
3             if(receive.Data != null)
4                 this.AppendText("DataReceived state="+receive.State+" topic="+ receive.Data.Topic + " content=" + System.Text.Encoding.UTF8.GetString(receive.Data.Reload));
5             else if(receive.State)
6                 this.AppendText("DataReceived state=" + receive.State + " result=" + receive.Result);
7             else
8                 this.AppendText("DataReceived state=" + receive.State + " fail=" + receive.Fail);
9         }

 

至此，客戶端工具主要功能簡介完畢，不當之處，歡迎指正！

客戶端下載地址（碼雲服務器）：https://gitee.com/ShiQuan25/full-product-management/raw/master/WinMQTTClient/WinMQTTClient.zip