mDNS Service Discovery

[igorquintal]

Hi everyone!
I'm working on a project which connects an ESP8266 to a Raspberry Pi, which is operating as a server. I want to make requests to the Raspberry from the ESP without knowing its IP address. The Raspberry host name is simply raspberrypi, and I'm able to make requests using this hostname through Postman or any other browsers.
The strange thing is: if I use my own WiFi, and try http.begin("raspberrypi.local", 3000, "/test");, I cannot access the server, I get an error. If I use raspberry's IP address, it works perfectly.
But what is really strange is that if I start a HotSpot with my Android phone, and connect the ESP8266 and the Raspberry, and try http.begin("raspberrypi.local", 3000, "/test");, it WORKS!! The Raspberry is also running Avahi, but things don't work unless I'm on my Android hotspot (I tested other WiFi networks with no success).
I was told to use the mDNS library, but that does not seem to work. Is there anyway someone could help me out?
Thanks!

[devyte]

Closing in view of #5442 with a full rewrite of mdns.