Netcode for GameObjects vs netcode.io

Netcode for GameObjects is Unity’s high-level networking library for synchronizing GameObjects and world data during multiplayer sessions. Unity describes it as suited to games with smaller player counts and less complex game logic, including adding multiplayer to an existing GameObject-based single-player game. Networking can use client- or server-authoritative models. NetworkBehaviour components use NetworkVariables to synchronize state and RPCs to send messages over the network. Integrated scene management is enabled by default and synchronizes scenes across connected clients. Unity Transport is the default transport, while Unity Relay can provide Relay networking for GameObject and MonoBehaviour workflows. Unity Multiplayer Services sessions are compatible with the package, which handles gameplay state replication after players connect. The package is free, but installation requires an active Unity account with a valid license, a supported Unity version, and an existing project. Supported platforms listed include Windows, macOS, Linux, iOS, Android, XR platforms on those systems, most closed platforms, and WebGL with specified package versions. There is no matchmaking functionality; developers must use third-party services for matchmaking. A full client-side prediction and reconciliation system must also be built by the developer.

netcode.io is a free, open-source client/server protocol for real-time multiplayer games. It uses UDP to exchange unreliable, unordered packets without TCP head-of-line blocking. Game backends can issue connect tokens that authorize clients, while servers assign connecting clients to configured slots and reject connections when slots are full. The protocol supports clean disconnects and timeouts for hard disconnects. Packets are encrypted and signed with libsodium, with protections described against crafted packets, replay attacks, and amplification attacks. IPv4 and IPv6 are supported, along with packet tagging intended to reduce Wi-Fi jitter. Implementations are listed for C, C#, Go, Rust, Unity, Unreal Engine 4, and TypeScript. Builds use CMake on Windows, macOS, and Linux, with CMake 3.16 or later and a vendored libsodium subset by default. The BSD 3-Clause project documents REST-based token requests and reports a nonce-reuse issue affecting versions 1.3.5 and earlier, fixed in 1.4.0.