Modified the expression as shown below and solved this case...
private bool IsUrlValid(string url)
{
Regex urlRx = new Regex(@"^https?://(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?):?(6553[0-5]|655[0-2]\d|65[0-4]\d{2}|6[0-4]\d{3}|[1-5]\d{4}|[1-9]\d{0,3})/$", RegexOptions.IgnoreCase);
return urlRx.IsMatch(url);
}
Thanks
Sebastian