using System;

using System.Globalization; //NumberStyles

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        int inputLength = 428;

        string Msg = "Data";

        byte[] Hdrbytes = new byte[6];//header

        string strLength = "00000000" + Convert.ToString(inputLength,16);// HEX以兩碼代表, 規格有4bytes, 因此補8個0來防呆

        strLength = strLength.Substring(strLength.Length - 8, 8);

        Hdrbytes[0] = 0x04 ;

        Hdrbytes[1] = 0x20 ;

        Hdrbytes[2] = byte.Parse(strLength.Substring(0, 2), NumberStyles.HexNumber);

        Hdrbytes[3] = byte.Parse(strLength.Substring(2, 2), NumberStyles.HexNumber);

        Hdrbytes[4] = byte.Parse(strLength.Substring(4, 2), NumberStyles.HexNumber);

        Hdrbytes[5] = byte.Parse(strLength.Substring(6, 2), NumberStyles.HexNumber);                

        string HdrStr = System.Text.Encoding.ASCII.GetString(Hdrbytes);

        Console.WriteLine(HdrStr);

        string bfr = HdrStr + Msg + "\x03";   

        Console.WriteLine(bfr);

        byte[] msg = System.Text.Encoding.ASCII.GetBytes(bfr);  

    }

}