[Gllug] sorts of ports

[tet at accucard.com]

>when you say 'what ports are open' is this the same as what apps are
>running? because that's my whole 'don't understand' thing.

Pretty much. An application essentially registers itself with the OS
to receive traffic sent to a given port. Once this is done, the port
is considered "open". The OS will direct all traffic that arrives on
that port to the application in question. By convention, certain
applications use particular ports. These are called "well known"
ports. Take a look in /etc/services to see some examples.

Thus, when the telnet daemon starts, it registers to listen on port 23.
So port 23 will be "open". Note however, that this is just convention.
You could run telnet on a completely different port, and you could run
something else (e.g., an FTP daemon) on port 23. But doing so doesn't
buy you much, except a false sense of security...

Tet

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