基于.net C# Socket WinForm MQTT 客户端开发

1、什么是MQTT？
　　MQTT（Message Queuing Telemetry Transport，消息队列遥测传输协议），是一种基于发布/订阅（publish/subscribe）模式的"轻量级"通讯协议，该协议构建于TCP/IP协议上，由IBM在1999年发布。MQTT最大优点在于，可以以极少的代码和有限的带宽，为连接远程设备提供实时可靠的消息服务。作为一种低开销、低带宽占用的即时通讯协议，使其在物联网、小型设备、移动应用等方面有较广泛的应用。

　　MQTT是一个基于客户端-服务器的消息发布/订阅传输协议。MQTT协议是轻量、简单、开放和易于实现的，这些特点使它适用范围非常广泛。在很多情况下，包括受限的环境中，如：机器与机器（M2M）通信和物联网（IoT）。其在，通过卫星链路通信传感器、偶尔拨号的医疗设备、智能家居、及一些小型化设备中已广泛使用。
（具体描述自行百度）

　　本文将基于.Net C# Socket WinForm MQTT 客户端开发，实现服务端连接，消息发布，消息订阅，取消订阅及接收服务端返回消息功能。

2、连接服务端

　　客户端连接服务端，启动异步接收服务端消息。

 1                     //连接选项

 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                     //实例客户端

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                     //开始接收

20                     this.mqttClient.BeginReceive();

3、发布消息

　　客户端向服务端发送消息，主要包括主题，内容及消息质量。

　　发送消息程序

 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("发送失败：" + result.Fail);

25                     return;

26                 }

27                 this._PacketId++;

28                 this.AppendText("发送成功，返回结果：" + result.Result);

29             }

30             finally

31             {

32                 this.btnPublish.Enabled = true;

33                 this.Cursor = Cursors.Default;

34             }

35         }

4、订阅消息

　　客户端订阅消息，主要包括过滤主题及消息质量。

　　订阅消息方法：

 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("开始订阅...");

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("订阅成功！返回结果：" + 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、取消订阅

　　客户端取消某一订阅消息。双击订阅消息行，取消订阅消息。

　　取消订阅方法：

 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("确认取消当前选择：" + drv["Filter"].ToString() + " 订阅?", "确认", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)

11                 return;

12             try

13             {

14                 this.AppendText("开始取消订阅...");

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("取消订阅成功！返回结果：" + 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("取消订阅异常：" + ex.ToString());

28             }

29

30         }

6、接收服务端消息

　　客户端接收服务端转发过来的消息。

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，客户端工具主要功能简介完毕，不当之处，欢迎指正！

客户端下载地址（码云服务器）：https://gitee.com/ShiQuan25/full-product-management/raw/master/WinMQTTClient/WinMQTTClient.zip

巴特西

基于.net C# Socket WinForm MQTT 客户端开发

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