ENet

Enet is a lightweight networking library designed for real-time multiplayer applications, primarily written in C. It provides a simple, reliable, message-oriented API over the User Datagram Protocol (UDP), enabling games and simulations to send small, frequent updates with predictable latency. ENet supports both reliable and unreliable delivery modes and allows multiplexing data over multiple channels to preserve ordering per channel while reducing head-of-line blocking.

The core concepts are hosts, peers, and channels. A host binds to a local port and manages connections to one or more peers. Each connection yields an ENetPacket that can be flagged as reliable or unreliable. Reliability is achieved via per-channel sequencing, acknowledgments, and retransmission; fragmentation is supported so large messages can be split into smaller packets.

ENet uses a lightweight event loop. Applications poll for events (connect, disconnect, receive) via a service function, enabling integration with game loops. It is designed to minimize CPU usage and provide steady throughput suitable for real-time simulations.

Platform and usage: ENet is cross-platform and written in C, with bindings to other languages. It has been used in a variety of real-time multiplayer projects and games, particularly where low latency is critical. The library emphasizes simplicity and performance, offering a compact API and predictable behavior at scale.

History and licensing: ENet originated as a standalone networking library for low-latency applications and has since seen broad adoption and contributions from the community. The project is open-source and maintained in public repositories.