1.6.4 is an update that fixed a bug where structures wouldn`t save with the world file.
- Added server.properties option player-idle-timeout
- Kicks players from a server when they idle for a set amount of minutes, defaults to disabled (0).
2 bugs fixed
- MC-15547 ⃢₀ₓ Structures (witch huts, nether fortresses etc.) don`t get saved with the world file
- In order for current structures (Witch Huts, Nether Fortresses, etc.) to be saved to the world file, the player must load the appropriate chunks within the game manually. The game will not automatically scan worlds and update structure data globally. After this is completed, structures will be compatible in all snapshots starting at Snapshot 13w37b
- Fixed handshake exploit