tcpdump

tcpdump is a powerful command-line packet analyzer.

IP traffic.

tcpdump host 1.1.1.1
tcpdump src 1.1.1.1
tcpdump dst 1.1.1.1

Port traffic.

tcpdump port 1234
tcpdump src port 1234
tcpdump dst port 1234
tcpdump portrange 8080-9090

Protocol traffic.

tcpdump udp

Network traffic.

tcpdump net 1.2.3.0/24

IP6 traffic.

tcpdump ip6

Interface traffic.

tcpdump -i eth0

Writing and reading to a file.

tcpdump -w file.txt
tcpdump -r file.txt

Conditions.

and
or
not

Options.

-q Quiet
-v Verbose