I'm just doing a bit of research into tech to use for a mobile multi-player game.
It's more an experiment at present so for the moment, the only thing that Players need to be aware of is the other Players.
If this was a typical web application and not a game It'd just have HTTP requests firing all the time -- but since this is a game, performance and accuracy is going to be a problem.
Each player will need to make the equivalent of a HTTP post and get only using a faster protocol. The reason for multiplayer being web based is because multiplayer across Bluetooth or other local networking would be too diverse across the platforms and could cause problems.