This is a little HTTP/1.1 library written from scratch in Python, heavily inspired by hyper-h2. It's a "bring-your-own-I/O" library; h11 contains no IO code whatsoever. This means you can hook h11 up to your favorite network API, and that could be anything you want: synchronous, threaded, asynchronous, or your own implementation of RFC 6214 - h11 won't judge you. (Compare this to the current state of the art, where every time a new network API comes along then someone gets to start over reimplementing the entire HTTP protocol from scratch.)