Port numbers 1-255 are reserved for standard Internet applications (like
ftp) and port numbers 256-1023 are reserved for standard Unix remote
services (which are often available for machines other than Unix).  You
should never choose any of these port numbers for your application unless
it is an implementation of a standard for which the port number is
reserved.  For more information on port numbering and reserved ports, see
the "References" section at the end of this article.