LAN on iOS without manually entering IP when connecting

Hi!

I'm going to make a game that is supposed to be played from different devices on a LAN. I assume one of the devices must act like a host and the other as clients that connect to this host. I want to be able to let them all connect without manually entering IP or things like that. Preferably if the devices could just have like a "Host" and "Join" button and the game will do everything for the users assuming the devices are on the same wifi.

Are there any ways to implement this for free? If not, what payed implementations would be most reliable? Thank you very much!