Tcpdump
To anylyse network traffic on a linux box you can use tcpdump. You should be root to see all packets ...
tcpdump -i eth0 -XX -s 0 -v port 80 >/tmp/tcpdump.txt
The syntax is not really intuitive. To analyse some web-traffic on port 80 you can use the command above. Be sure to use the parameter "-s 0" to see the whole packets - otherwise the tool cuts after 68 bytes.
