I'm working on a server (modded) which requires you to have a custom launcher that uses my own authentication servers, instead of Mojang's. So basically I want a way to be able to get the player's session ID when he/she logs in to the server. I'm not trying to hijack sessions.
So far, I tried subscribing to the PlayerLoggedIn event, but there was no session ID in event.player. Then I tried casting it to EntityPlayerMP, and still couldn't find any session ID.