Yeah I used to use wireshark (and under its prior name of ethereal or whatever it was) a lot and less so nowadays as I do less network development, but it was super useful. tcpdump is also useful but need other tools to parse through it, lol.

I’ve used Wireshark at home, and at work. At work it was very useful for analyzing a (relatively unique) network protocol for some older systems. You can extend it so that it recognizes different protocols and can breakdown the packets (so that our custom protocol stopped being a hex blob and became actual useful information). With that, we could do a lot of filtering in Wireshark to monitor things during test and development.

I used it in high school to sniff traffic and read the communication on the most popular IM in Poland at the time (it used plain-text communication so it was dumb easy with ARP spoofing).