The only operations that can be applied to port
values are
relationals. You may compare them for equality, and also for ordering.
For example,
20/tcp < telnet
yields true because telnet
is a predefined constant set to
23/tcp
.
When comparing ports across transport-level protocols, the following
holds: unknown < TCP < UDP < ICMP. For example, “65535/tcp
” is
smaller than “0/udp
”.