serialport 开发 rs232脚 COM1 接口程序，寄信测试成功，但就是接收不到信息，请前辈出手相救！万分感谢！

 public Form1()
        {
            InitializeComponent();
        }

      
        //初始化SerialPort对象方法.PortName为COM口名称,例如"COM1","COM2"等,注意是string类型
       public void InitCOM(string PortName)
         {
             serialPort1 = new SerialPort(PortName);
             serialPort1.BaudRate = 9600;//波特率
             serialPort1.Parity = Parity.None;//无奇偶校验位
             serialPort1.StopBits = StopBits.Two;//两个停止位
             serialPort1.Handshake = Handshake.RequestToSend;//控制协议
             serialPort1.ReceivedBytesThreshold = 4;//设置 DataReceived 事件发生前内部输入缓冲区中的字节数
           
        }

        
 
         //打开串口的方法
         public void OpenPort()
         {
             try
             {
                 serialPort1.Open();
             }
             catch { }
             if (serialPort1.IsOpen)
             {
                 Console.WriteLine("the port is opened!");
             }
             else
            {
                 Console.WriteLine("failure to open the port!");
             }
         }

         //关闭串口的方法
         public void ClosePort()
         {
             serialPort1.Close();
             if (!serialPort1.IsOpen)
            {
                 Console.WriteLine("the port is already closed!");
             }
        }
  
        
         
         //调用实例,发送数据
        
        private void button1_Click(object sender, EventArgs e)
        {
            InitCOM("COM3");
            OpenPort();

            byte[] data = Encoding.Unicode.GetBytes(this.textBox1.Text);
            string str = Convert.ToBase64String(data);
            serialPort1.WriteLine(str);
            ClosePort();
            MessageBox.Show(this, "利用串口成功发送数据！", "信息提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

        }

        //接收数据
        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
                byte[] datar = Convert.FromBase64String(serialPort1.ReadLine());
                textBox2.Text = Encoding.Unicode.GetString(datar);
                ClosePort();
                MessageBox.Show(this, "利用串口成功接收数据！", "信息提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            catch
            {
                ClosePort();
                MessageBox.Show(this, "利用串口接收数据失败！", "信息提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }