using System.IO.Ports;

public class Program

{

    public static void Main()

    {

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

        port.Open();

    byte[] data = { 0, 1, 2, 1, 0 };

        port.Write(data, 0, data.Length);

        port.Close();

    }

}