tcpdump
tutorial
http://openmaniak.com/tcpdump.php
list all traffic
sudo tcpdump
list all interfaces
sudo tcpdump -D
log traffic on interface eth0
sudo tcpdump -i eth0
list traffic on certain port
sudo tcpdump port 443
show ip-addresses instead of DNS names
sudo tcpdump -n
traffic from src ip on port
sudo tcpdump port 443 and src 217.149.135.12