Re: tcpdump equivalent for the serial port

[Jan-Benedict Glaw <jbglaw@lug-owl.de>]

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On Fri, 2003-09-12 15:37:24 +0200, Nicolae Mihalache <mache@abcpages.com>
wrote in message <3F61CC14.20607@abcpages.com>:
> Hello!
> 
> I'm interested if somebody has any ideea how to write a program that 
> is able to sniff the data passing through a serial port the same way 
> tcpdump is able to show the data passing through the ethernet cable, 
> i.e. without disturbing the application that sends/receives the data.
> I've seen few programs that basically work as tunnels opening a 
> pseudo-console where the application connects and writing on the other 
> side to the serial device. This approach is not very useful because I 
> want to be able to start/stop my sniffer without interupting the 
> communication and also the application can control different settings 
> of the serial port which probably will not be forwarded by the tunnel.

Your approach won't work, but I can hint you to another. If you don't
need the *wire states*, but only the data your application receives (or
transmits), then this is easy. Simply use strace or a preload lib to
intercept open, close, read and write.

That way, you don't monitor the serial port itself, but the application
using it. For me, that has always been enough:-)

MfG, JBG

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   Jan-Benedict Glaw       jbglaw@lug-owl.de    . +49-172-7608481
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