ENet's purpose is to provide a relatively thin, simple and robust network communication layer on top of UDP (User Datagram Protocol). The primary feature it provides is optional reliable, in-order delivery of packets.

ENet is NOT intended to be a general purpose high level networking library that handles authentication, lobbying, server discovery, compression, encryption and other high level, often application level or dependent tasks.

Features and Architecture

ENet evolved specifically as a UDP networking layer for the multiplayer first person shooter Cube. Cube necessitated low latency communcation with data sent out very frequently, so TCP was an unsuitable choice due to its high latency and stream orientation. UDP, however, lacks many sometimes necessary features from TCP such as reliability, sequencing, unrestricted packet sizes, and connection management. So UDP by itself was not suitable as a network protocol either. No suitable freely available networking libraries existed at the time of ENet's creation to fill this niche.

UDP and TCP could have been used together in Cube to benefit somewhat from both of their features, however, the resulting combinations of protocols still leaves much to be desired. TCP lacks multiple streams of communication without resorting to opening many sockets and complicates delineation of packets due to its buffering behavior. UDP lacks sequencing, connection management, management of bandwidth resources, and imposes limitations on the size of packets. A significant investment is required to integrate these two protocols, and the end result is worse off in features and performance than the uniform protocol presented by ENet.

ENet thus attempts to address these issues and provide a single, uniform protocol layered over UDP to the developer with the best features of UDP and TCP as well as some useful features neither provide, with a much cleaner integration than any resulting from a mixture of UDP and TCP.