I am not sure if it is posted anywhere, but if you ever paid attention to the time you could figure it out.

One thing you should be aware of is if you try and refresh the opponents screen in the arena and come across the connect issue, log out of the game. If you try and refresh again it usually cost you ironite without warning. Sometimes if you log out and come back the opponents screen maybe refreshed. If the opponents didnt change you can refresh again for free.