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3.8.2 Port Operators

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”.