private void buttonOpenClose_Click(object sender, EventArgs e)
        {
            if (buttonOpenClose.Text == "关闭")
            {
                if (comm.IsOpen)
                {
                    comm.Close();
                }
                buttonOpenClose.Text = "打开";
                return;
            }
            //根据当前串口对象,来判断操作
            if (comm == null)
            {
                //关闭时点击,则设置好端口,波特率后打开
                comm.PortName        = comboPortName.Text;
                comm.BaudRate        = int.Parse(comboBaudrate.Text);
                comm.DataBits        = 8;
                comm.Parity          = Parity.None;
                comm.StopBits        = StopBits.One;
                comm.WriteBufferSize = 1024 * 1024 * 5;
                comm.ReadBufferSize  = 1024 * 1024 * 5;
                try
                {
                    comm.Open();
                    MessageBox.Show("串口已打开");
                }
                catch (Exception ex)
                {
                    //捕获到异常信息,创建一个新的comm对象,之前的不能用了。
                    comm = new SerialPort();
                    //现实异常信息给客户。
                    MessageBox.Show(ex.Message);
                }
            }
            else
            {
                if (comm.IsOpen)
                {
                    while (CVar.GetCommBusy())
                    {
                        Application.DoEvents();
                    }
                    //打开时点击,则关闭串口
                    comm.Close();
                    MessageBox.Show("串口已关闭");
                }
                else
                {
                    //关闭时点击,则设置好端口,波特率后打开
                    comm.PortName        = comboPortName.Text;
                    comm.BaudRate        = int.Parse(comboBaudrate.Text);
                    comm.DataBits        = 8;
                    comm.Parity          = Parity.Even;
                    comm.StopBits        = StopBits.One;
                    comm.WriteBufferSize = 1024 * 1024 * 5;
                    comm.ReadBufferSize  = 1024 * 1024 * 5;
                    try
                    {
                        comm.Open();
                        MessageBox.Show("串口已打开");
                    }
                    catch (Exception ex)
                    {
                        //捕获到异常信息,创建一个新的comm对象,之前的不能用了。
                        comm = new SerialPort();
                        //现实异常信息给客户。
                        MessageBox.Show(ex.Message);
                    }
                }
            }
            //设置按钮的状态
            buttonOpenClose.Text = comm.IsOpen ?  "关闭" : "打开";

            if (comm.IsOpen)
            {
                CommPara.portnum  = comm.PortName;
                CommPara.baudrate = comm.BaudRate;
                CommPara.ParaWrite();
                CVar.form1.button1.Text = CommPara.portnum.ToString() + "已打开";
                comm.DataReceived      += CVar.form1.comm_DataReceived;
            }
        }