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Subsections

- Port Constants
- Port Operators

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Port Type

The `port` type corresponds to a TCP or UDP port number. TCP and UDP ports are distinct. Thus, a value of type `port` can hold either a TCP or a UDP port, but at any given time it is holding exactly one of these.

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Port Constants

There are two forms of `port` constants. The first consists of an unsigned integer followed by either ```/tcp`'' or ```/udp`.'' So, for example, ```80/tcp`'' corresponds to TCP port 80 (the HTTP protocol used by the World Wide Web). The second form of constant is specified using a predefined identifier, such as ```http`'', equivalent to ```80/tcp`.'' These predefined identifiers are simply `const` variables defined in the Bro initialization file (§ ), such as:

        const http = 80/tcp;

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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`.

UDP ports are considered larger than TCP ports, i.e., ```0/udp`'' is larger than ```65535/tcp`''.

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