I'm currently working on a friend system which allows you to challenge a friend from the Friend List. Create and join the room is not a problem, because Photon lets you to open a room for a specific player.
I need a way to notify that a friend is challenging me. PlayFab works using http requests, then I suppose I have to poll between a undefined time if a friend sent me a challenge. The question is, which is the best way to get it?
First, I thought that Matchmake with both players id in Tags parameter could be a good solution. But it forces you to write an IP address and port, and this makes me uncertain. Other options I'm managing are writing directly in challenged player Players Data, but sounds odd. Shared Data is another option. Maybe a Push Notification among both players?