A socket question

Jason Orendorff jason at jorendorff.com
Wed Jan 16 13:55:08 EST 2002

> >According to Robin Munn <rmunn at pobox.com>:
> >> "exceptional conditions" (I don't know what constitutes an "exceptional
> >> condition" on a TCP/IP socket; one of the RFC's should be able to tell
> >> you).
> >
> >OOB data. On the wire these will be TCP segments with the URG flag on.
> Thanks! I've never written an application where out-of-band data was
> necessary, so I didn't know that. Has anyone used this in practice? What
> is it good for?

Not much.  The Telnet protocol has some details that make use of
URGent data, but as far as I can tell, those particular details
don't see much use these days.

I'm sure someone will correct me if I'm wrong... :-)

Also, the TCP "URGent pointer" feature isn't "true" out-of-band data.
TCP doesn't really support out-of-band data (although you can
of course just open a second TCP connection.)

## Jason Orendorff    http://www.jorendorff.com/

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