yojimbo is a C++ client/server network library for real-time
multiplayer games. It provides cryptographically secure client
authentication and encrypted packets (via netcode), reliable-ordered
messages and data blocks (via reliable), a bitpacked message
serialization system (via serialize), client slot management, and
pluggable allocators that silo each client into its own heap.

Encryption and authentication are on by default: clients connect with
short-lived connect tokens issued by a trusted backend, so only
authenticated clients can talk to the server.