The follow example shows how to use regexp to validate IP address.

program RegExpIP;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  RegularExpressions;

var
 ipRegExp : String;
begin
  try

    ipRegExp := '\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b';

  if TRegEx.IsMatch(paramstr(1), ipRegExp) then
    Writeln('Text DOES match the regular expression')
  else
    Writeln('Text DOES NOT match the regular expression');

  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

Just execute the program and pass the IP address as parameter.

In this case the IP address is valid
RegExpIP 200.100.2.21
Text DOES match the regular expression

In this case not, the IP address finish with 263, it is out of the range which is 255
RegExpIP 200.100.2.263
Text DOES NOT match the regular expression

On the RAD Studio demo repository at sourceforge you can find a project sample showing other regular expressions that you can use.

As well download the Delphi XE trial and start looking the other great features on this release,  download the trial here

Andreano Lanusse | Technology and Software Development Follow me on Twitter: @andreanolanusse