Open Source C KCP Software

Like libevent, libev, and libuv, libhv provides event loop with non-blocking IO and timer, but simpler api and richer protocols. Cross-platform (Linux, Windows, MacOS, BSD, Solaris, Android, iOS) High-performance EventLoop (IO, timer, idle, custom) TCP/UDP client/server/proxy. TCP supports heartbeat, reconnect, upstream, MultiThread-safe write and close, etc. Built-in common unpacking modes (FixedLength, Delimiter, LengthField) RUDP support: WITH_KCP. SSL/TLS support: (via WITH_OPENSSL or WITH_GNUTLS or WITH_MBEDTLS) HTTP client/server (support https http1/x http2 grpc). HTTP supports static service, indexof service, proxy service, sync/async API handler. HTTP supports RESTful, router, middleware, keep-alive, chunked, SSE, etc. WebSocket client/server.

KCP is a fast and reliable protocol that can achieve the transmission effect of a reduction of the average latency by 30% to 40% and reduction of the maximum delay by a factor of three, at the cost of 10% to 20% more bandwidth wasted than TCP. It is implemented by using the pure algorithm, and is not responsible for the sending and receiving of the underlying protocol (such as UDP), requiring the users to define their own transmission mode for the underlying data packet, and provide it to KCP in the way of callback. Even the clock needs to be passed in from the outside, without any internal system calls. The entire protocol has only two source files of ikcp.h, ikcp.c, which can be easily integrated into the user's own protocol stack. You may have implement a P2P, or a UDP-based protocol, but are lack of a set of perfect ARQ reliable protocol implementation, then by simply copying the two files to the existing project, and writing a couple of lines of code, you can use it.

xkcptun is a C-language implementation of kcptun built on KCP and libevent2. It is mainly designed for embedded and router-oriented environments such as LEDE and OpenWrt, where lightweight networking tools are often preferred. The project provides client and server components that use KCP-based tunneling to improve performance over unreliable or high-latency network links. It also includes a spy utility, making the generated build more than a minimal two-binary tunnel setup. xkcptun can be built with CMake and supports static linking for easier deployment on constrained systems. It is most relevant to users who need a compact KCP tunnel implementation for routers, gateways, and custom network appliances.