A simple way to check whether an IP address is valid.

function IsIPAddress(zvIPAddressID: string): boolean;
var
  ipLengthOfGroup, ipPosition, ipNoOfGroups: integer;
  ipGroupNum, Code: integer;
begin
  IsIpAddress := False;
  ipNoOfGroups := 0;
  ipLengthOfGroup := 0;
  for ipPosition := 1 to Length(zvIPAddressID) do
    case Ord(zvIPAddressID[ipPosition]) of
      48..57:
        begin
          inc(ipLengthOfGroup);
          if (ipLengthOfGroup > 3) then exit;
        end;
      46:
        begin
          inc(ipNoOfGroups);
          Val(Copy(zvIPAddressID, ipPosition - ipLengthOfGroup, ipLengthOfGroup), ipGroupNum, Code);
          if ((ipNoOfGroups > 3) or (ipLengthOfGroup = 0)) or (ipGroupNum > 255) then exit;
          ipLengthOfGroup := 0;
        end;
      else
        exit;
    end;
  Val(Copy(zvIPAddressID, ipPosition - ipLengthOfGroup, ipLengthOfGroup), ipGroupNum, Code);
  IsIPAddress := (ipNoOfGroups = 3) and (ipLengthOfGroup > 0) and (ipGroupNum < 256);
end;