[lug] tcpdump syntax

D. Stimits stimits at attbi.com
Fri Apr 11 22:01:15 MDT 2003

I'm trying to port a simple tcp/ip client from windows to linux, and I 
have most of it compiling, but I need to figure out some 
newline/carriage return/EOL and login order info, and not getting 
anywhere. I'm trying to use tcpdump on a linux bridge (device br0), but 
I'm getting flooded out by my ssh connect and other connects not related 
to the machine I want to watch. Filtering later with regular expressions 
and macros works, but is a complete pain since the dump patter is 
multiline. It looks like tcpdump should be able to dump data only for 
packets with a source or destination of some particular IP address, 
e.g., for IP, and nothing else, but I am at a loss. The 
following syntax works for all tcp and does not filter, though it does 
give the output I want buried in tons of data:
   tcpdump -n -vv -X -s 0 tcp

Now according to the tcpdump man page, the final argument to tcpdump can 
be an expression. I can get the expression to filter with tcp as shown 
above, but the syntax of anything other than this is failing, giving me 
a "tcpdump: parse error". I am not interested in the direction of 
movment, I am interested in all tcp going to or from address (sample) How would I extend this to limit it to only tcp:
   tcpdump -n -vv -X -s 0 'host'

D. Stimits, stimits AT attbi DOT com

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