So firstly there are a large number of operating system reserved ports in the range 0-1024, see http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers. e.g. It is generally considered bad practice to even attempt to use ports in this range as it can cause some operating system features to malfunction.
As to your specific problem please tell me what the specific exception type is that is being thrown?
Regards,
Marc