Any way to get an audio representation of packet flow?

Doug Lee dgl at
Tue Jan 25 01:04:10 PST 2005

Ok, this may be odd to many, but here's what I want:

I like tcpdump's powerful ways of selecting and analyzing specific
portions of packet traffic, but I want a real-time way to represent
the results.  I am blind, so graphs don't help. <grin>  Usually all I
want to know is the pattern of packet match frequency vs. time, so a
little click for each matching packet would translate nicely into what
I'm looking for.

My normal tactic involves directing output from tcpdump to /dev/audio
or even /dev/pcaudio:

tcpdump -l -n [... rules for traffic ...] >/dev/audio

is the first trick I tried.  Problem:  It causes me to get kernel
errors like "runt packet" and such, presumably because it adds too
mmuch overhead to packet processing somehow.  (This is a P166; maybe
that problem wouldn't exist on faster hardware?)

My next trick was like

tcpdump -s 1 -w /dev/audio [... rules for traffic ...]

No errors this time, but the output of -w is buffered regardless of -l
(which normally makes a lot of sense, of course), so it wasn't very

I currently run FreeBSD 4.10-STABLE, but I'd be interested in any
solutions requiring 5.x features as well, for future planning.

Please Cc me if you have any ideas.

Thanks much.

Doug Lee           dgl at
Bartimaeus Group   doug at
The very smart may feel they have nothing to learn from anyone;
The very wise will find something to learn from everyone.  (7/14/01)

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