using System;
using System.Text.RegularExpressions;

public class Example
{
    public static void Main()
    {
        string pattern = @"([A-Z0-9]{4})";
        string input = @" ;   Message Number
    ;   |         Time Offset (ms)
    ;   |         |        Type
    ;   |         |        |        ID (hex)
    ;   |         |        |        |     Data Length
    ;   |         |        |        |     |   Data Bytes (hex) ...
    ;   |         |        |        |     |   |
    ;---+--   ----+----  --+--  ----+---  +  -+ -- -- -- -- -- -- --
         1)         2.0  Rx         0400  8  01 5A 01 57 01 D2 A6 02 
         2)         8.6  Rx         0500  8  02 C1 02 C9 02 BE 02 C2 
         3)        36.2  Rx         0401  8  01 58 01 59 01 01 01 01 
         4)        41.7  Rx         01C4  8  27 9C 64 8C 00 03 E8 08 
         5)        43.1  Rx         0501  8  02 C0 02 C1 02 C6 02 C0 
         6)        62.7  Rx         01C2  8  27 9C 60 90 00 0F 04 08 ";
        RegexOptions options = RegexOptions.Multiline;

        foreach (Match m in Regex.Matches(input, pattern, options))
        {
            Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
        }
    }
}