tshark

Packet analysis tool, CLI version of Wireshark. More information: https://tshark.dev/.

Monitor everything on localhost:

tshark
Only capture packets matching a specific capture filter:

tshark -f '{{udp port 53}}'
Only show packets matching a specific output filter:

tshark -Y '{{http.request.method == "GET"}}'
Decode a TCP port using a specific protocol (e.g. HTTP):

tshark -d tcp.port=={{8888}},{{http}}
Specify the format of captured output:

tshark -T {{json|text|ps|…}}
Select specific fields to output:

tshark -T {{fields|ek|json|pdml}} -e {{http.request.method}} -e {{ip.src}}
Write captured packet to a file:

tshark -w {{path/to/file}}
Analyze packets from a file:

tshark -r {{filename}}.pcap