public static SerialPort port = new SerialPort("COM4", 9600, Parity.None, 8, StopBits.One);

    static byte[] Opne_port = new byte[] { 0xA0, 0x01, 0x01, 0xA2};
    static byte[] Close_port = new byte[] { 0xA0, 0x01, 0x00, 0xA1 };

private void button1_Click(object sender, EventArgs e) {

        port.Open();
      //  port.Write(1, 01, 01);
        
        port.Write(Opne_port, 0, 4);
        System.Threading.Thread.Sleep(3000);
       // port.Write(Close_port, 0, 4);
        // Thread.Sleep(500);
    }