Failed to Login: Invalid Session
There are two solutions:
- Disable Minecraft's account verification checks on the server:
Doing this breaks Minecrafts EULA and also makes it significantly easier for people with malicious intentions (such as hackers, exploiters and griefers) to join your server and rejoin after being banned. It's not recommended that you add support for cracked accounts unless you really trust your playerbase.
server.properties file on your server, then open it and locate the
online-mode=true line, and change it to
online-mode=false. Restart your server and voila! Cracked accounts can now join your server.
- Tell the players to buy Minecraft and connect to the server with a non-cracked account.