My friend made a minecraft server(Vanilla) today. We were playing survival on it, no mods, no nothing. From out of no where I get kicked and it says "You have been idle for too long." I was never idle and we were building our house in minecraft. Then 5 seconds later my friend also gets kicked for being "idle". No error logs in the server, there is just logs of me getting disconnected, and getting disconnected for being idle. We also use hamachi for connecting to each others servers. But that wouldn't matter for my friend who is connecting via localhost.
UPDATE: When my friend wrote "/setidletimeout 0" everything worked fine. But we had never touched the idletimeout setting.