Wireshark

Ex Ethereal

http://www.wireshark.org

http://www.wireshark.org/news/20060607.html

Discussion

http://www.howtogeek.com/107945/how-to-identify-network-abuse-with-wireshark
http://opensourceforu.com/2017/08/beginners-guide-wireshark-top-rated-packet-sniffer
http://www.networkcomputing.com/networking/using-wireshark-test-troubleshooting-tools/287546826

https://www.networkcomputing.com/networking/wireshark-configuring-interface-displays/191755580

https://www.csoonline.com/article/3305805/network-security/what-is-wireshark-what-this-essential-troubleshooting-tool-does-and-how-to-use-it.html

https://www.networkcomputing.com/networking/navigating-wireshark/85585235