Design advice for restful darts-game communication

I am thinking of a simple x01 darts game rest api for two players. I am pretty clear on how to implement the darts business logic. But I struggle thinking about a session-like communication between the players in order to let player a wait for player b to finish its turn. After my research I did not came up with a pattern to apply here, nor if its a restful antipattern. So any advice is appreciated how something like mentioned could be realised.