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。

                    //连接选项
                    var option = new MQTT.MQTTClientOption()
                    {
                        ClientId = this.txtClientId.Text,
                        IpString = this.txtServer.Text,
                        Port = Convert.ToInt32(this.txtPort.Text),
                        UserName = this.txtUserName.Text,
                        Password = this.txtPassword.Text
                    };
                    //实例客户端
                    this.mqttClient = new MQTT.MQTTClient();
                    this.mqttClient.ClientReceived += MqttClient_ClientReceived;
                    var result = await this.mqttClient.ConnectAsync(option);
                    if(result.State == false)
                    {
                        MessageBox.Show(result.Fail, "提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                        return;
                    }
                    //开始接收
                    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

        private short _PacketId = 1;
        private async void BtnPublish_Click(object sender, EventArgs e)
        {
            this.btnPublish.Enabled = false;
            this.Cursor = Cursors.WaitCursor;
            try
            {
                short qos = 0;
                if (rdbLevel1.Checked)
                    qos = 1;
                if (rdbLevel2.Checked)
                    qos = 2;
                
                var data = new MQTT.PublishEntity()
                {
                    Topic = this.txtTopic.Text,
                    Reload = System.Text.Encoding.UTF8.GetBytes(this.txtContent.Text),
                    Qos = qos,
                    PacketId=_PacketId
                };
                var result = await this.mqttClient.PublishAsync(data,false);
                if(result.State == false)
                {
                    this.AppendText("发送失败：" + result.Fail);
                    return;
                }
                this._PacketId++;
                this.AppendText("发送成功，返回结果：" + result.Result);
            }
            finally
            {
                this.btnPublish.Enabled = true;
                this.Cursor = Cursors.Default;
            }
        }

 

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：

private async void BtnSubscribe_Click(object sender, EventArgs e)
        {
            this.btnSubscribe.Enabled = false;
            this.Cursor = Cursors.WaitCursor;
           
            try
            {
                string fail = string.Empty;

                short qos = 0;
                if (rdbQos1.Checked)
                    qos = 1;
                if (rdbQos2.Checked)
                    qos = 2;

                MQTT.SubscribeEntity entity = new MQTT.SubscribeEntity();
                entity.Filter = this.txtFilter.Text;
                entity.Qos = qos;

                this.AppendText("开始订阅...");
                //if (mqttClient.Subscribe(this.txtFilter.Text, qos, out result, out fail) == false)
                //{
                //    this.AppendText(fail);
                //    return;
                //}
                var result = await mqttClient.SubscribeAsync(entity.Filter,entity.Qos);
                if (result.State == false)
                {
                    this.AppendText(result.Fail);
                    return;
                }
               
                this.AppendText("订阅成功！返回结果：" + result.Result);
                MQTT.SubscribeHelper.Save(entity);

                DataRow drData = this.dtSubscribes.NewRow();
                drData["Id"] = entity.Id;
                drData["Filter"] = entity.Filter;
                drData["Qos"] = entity.Qos;
                drData["Count"] = 0;
                dtSubscribes.Rows.Add(drData);
            }
            finally
            {
                this.btnSubscribe.Enabled = true;
                this.Cursor = Cursors.Default;
            }
        }

 

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：

        private async void DataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            if (this.dataGridView1.CurrentCell == null)
                return;

            DataRowView drv = this.dataGridView1.CurrentRow.DataBoundItem as DataRowView;
            if (drv == null)
                return;

            if (MessageBox.Show("确认取消当前选择：" + drv["Filter"].ToString() + " 订阅?", "确认", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
                return;
            try
            {
                this.AppendText("开始取消订阅...");
                var result = await mqttClient.UnSubscribeAsync(drv["Filter"].ToString());
                if (result.State == false)
                {
                    this.AppendText(result.Fail);
                    return;
                }
                this.AppendText("取消订阅成功！返回结果：" + result.Result);
                MQTT.SubscribeHelper.Delete(drv["Id"].ToString());
                this.dataGridView1.Rows.RemoveAt(this.dataGridView1.CurrentCell.RowIndex);
            }
            catch (Exception ex)
            {
                this.AppendText("取消订阅异常：" + ex.ToString());
            }

        }

 

6、接收服务端消息

　　客户端接收服务端转发过来的消息。

 

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

 

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