libuv is a multi-platform support library with a focus on asynchronous I/O.

Feature highlights:
 + Full-featured event loop backed by epoll, kqueue, IOCP, event ports.
 + Asynchronous TCP and UDP sockets
 + Asynchronous DNS resolution
 + Asynchronous file and file system operations
 + File system events
 + ANSI escape code controlled TTY
 + IPC with socket sharing, using Unix domain sockets or named pipes (Windows)
 + Child processes
 + Thread pool
 + Signal handling
 + High resolution clock
 + Threading and synchronization primitives

WWW: https://github.com/libuv/libuv
