Is there a way to check if the client is or isn't connected to Xbox? If so, how? I would like to make a simple login system to check and make sure all players that join are connected to Xbox for the surest way to make sure all players have different names.
No need to use the Xbox API, the authentication data that is sent if the player is using Xbox Live is already signed with Mojang's private key. All you have to do is decode the data with the Mojang public key -- if you're able to do so then you can verify that they are actually authenticated. You need to also verify the login time and the login expiration time to ensure that the client isn't using an expired session. https://confluence.yawk.at/display/PEPROTOCOL/Game Packets
