Open Source C# KCP Software

Mirror is a high-level open-source networking library for Unity multiplayer games. It was originally based on UNET and has evolved into a stable, modular framework used by many production Unity projects. The library is designed to make multiplayer development easier by handling common networking patterns such as network identities, synchronization, remote procedure calls, authority, spawning, and transport integration. Mirror supports multiple low-level transports, making it adaptable to different game genres and deployment needs. It is suitable for small multiplayer games, cooperative games, competitive prototypes, and even larger persistent-world or MMORPG-style projects. The project is especially useful for Unity developers who want a mature networking layer without building protocol and synchronization systems from scratch.

KumoKyaku KCP is a C# implementation of the KCP reliable UDP protocol designed for high-performance .NET applications. It provides ready-to-use APIs while also allowing advanced users to customize segment handling and memory behavior. The project uses unsafe code and unmanaged memory internally to reduce garbage collection pressure, which is important for real-time systems. It supports Span<byte>, external buffer rental, and a generic KcpCore<Segment> architecture for performance-focused implementations. The library is partly thread-safe, allowing concurrent Send and Input calls while restricting concurrent Recv and Update calls for correctness. It is useful for game networking, real-time communication, and other latency-sensitive C# applications that need reliable delivery over UDP.