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Subsections


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.


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;


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''.


next up previous contents index
Next: Address Type Up: Values, Types, and Constants Previous: Temporal Types   Contents   Index
Vern Paxson 2002-11-17