Fairy Fox
PaperMC Despawned Items/io.fairyfox.papermc.despawneditems.ui/ClientAccess/PROTOCOL_VERSION

PROTOCOL_VERSION

const val PROTOCOL_VERSION: Int = 1

Protocol revision. Sent in the handshake so a mod can refuse to talk to a server it does not understand — and so this plugin can evolve the wire format later without breaking older mods.