serial_sniffer -- Serial Sniffer allows you to sniff serial data
http://www.ibiblio.org/[..]inux/apps/serial_sniffer-0.5.tar.gz
serial_sniffer by Grahame M. Kelly (gmkelly zip.com.au)
The Linux Serial Sniffer allows you to sniff serial data up to 460Kbs
via a Comtrol RocketPort or to 115Kbs using the standard ttyS0 and ttyS1
ports. Sniffed output can be captured to disk or displayed directly on
screen. A user filter is included to assist specific customisation. The
Linux Serial Sniffer can selectively operate in either a "ghost mode"
where there is no data flow time impediments, or via a "capture and
forward mode", where the user can flexibily intercept and extend the
data stream to suit from either direction.