串口接收后发送指定的数字

 private void getData()
        {
            while(true)
            {

                //Thread.Sleep(1000);
                try{
                sp = new SerialPort();
               sp.PortName = portname;//串口编号
               sp.BaudRate = 9600;//波特率
               sp.StopBits = StopBits.One;//
               sp.DataBits = 8;//
               sp.Parity = Parity.None;//设置串口属性
               if (sp.IsOpen==false)
                   sp.Open();
               int gi = sp.ReadByte();
                 if (gi == 1)
                {
                    byte[] bu = { 129 };

                 sp.Write(bu, 0, bu.Length);                

               sp.Close();
            }
                catch{}
        }
           
        }