When trying to connect to localhost when offline, the connection fails with the message "Failed to login: The authentication servers are currently down for maintenance." I know this is not actually the case because I can connect just fine if I have a network connection. I realize that this probably can't be fixed due to security concerns, but I thought it was worth bringing up.
MC-82111
Authentication failure connecting to localhost
Resolved
Invalid
0
In the server.properties file, the option online-mode determines if authentication checking is needed. Without access to the internet, this will result in the messages you receive. Disabling this option will allow you to connect. Please note that your player data will be stored under a different UUID, since your actual UUID cannot be determined or verified.