Common error messages

A short reference for errors you'll see in the console.

"Can't keep up! Is the server overloaded?"

Your TPS dropped below 20 for too long. See Performance tuning.

"java.lang.OutOfMemoryError: Java heap space"

The JVM ran out of memory. Either your modpack is too heavy for your server size or a plugin is leaking memory. Restart and investigate; if it keeps happening, size up or remove suspects.

"Failed to bind to port"

Something is already using your assigned port. On Kyrbit this should never happen — open a ticket if it does.

"Disconnected: Outdated client" / "Outdated server"

Mismatched Minecraft versions between client and server. Update one to match the other.

"Invalid session"

The player's Minecraft client lost its session with Mojang's auth servers. They need to restart Minecraft or, in rare cases, restart the launcher. Not a server-side problem.

"Internal server error" (when joining)

A plugin or mod threw an exception during the join handler. Check the console for the stack trace at the same timestamp.