title: How to design application messaging service from one user to many users in game
body: <p>I'm making an application for Android that allows me to send a set of geolocation points from one user to a group of users playing a game together, but I don't really know where to start on sending the messages.</p>
  
  <p>I had one idea that involved sending the message from the one user to a server, and then having the server push the message to the other users, but I don't know how to let the server know which users to send the message to.</p>
  
  <p>Am I on the right track? Are there services already set up that deal with this kind of problem? Do you have any other suggestions? Your comments are appreciated.</p>