Wireshark

world’s foremost and widely-used network protocol analyzer

Wireshark
wireshark.org
https://www.wireshark.org/

Resources

Wireshark Tutorial for BEGINNERS // Where to start with Wireshark - YouTube
youtube.com
https://www.youtube.com/watch?v=OU-A2EmVrKQ
Learn Wireshark in 10 minutes - Wireshark Tutorial for Beginners - YouTube
youtube.com
https://www.youtube.com/watch?v=lb1Dw0elw0Q