Mdns
From Federal Burro of Information
automagical dns on local nets.
on a windows machine use this to discover services:
dns-sd -B _ssh._tcp
dns-sd -B _http._tcp
dns-sd -B _https._tcp
You can get arduino's to advertise their services like this:
https://github.com/arduino-libraries/ArduinoMDNS
https://tttapa.github.io/ESP8266/Chap08%20-%20mDNS.html
https://support.arduino.cc/hc/en-us/articles/4506515275548-About-mdns-discovery
I use this on my esp32's