#22 Fix #19 and #20 - Process ports correctly

I can confirm the bug not recognizing port numbers higher than 9999. Regarding the port number 0, I refer to [this page] [1]. Although using the port 0 is technically illegal, it is possible and used for OS fingerprinting. However, as we do not take consideration of the operating systems response, I think we can exclude this port. Thanks for the fix! [1]: http://www.speedguide.net/port.php?port