Supranim's HTTP server and WebSocket support are built on powpow, a high-performance event notification library written entirely in Nim. It provides TCP/UDP, HTTP/1.1 and WebSocket server capabilities and is the only backend shipped with Supranim.
The web server lives in supranim/network/webserver and the WebSocket support in supranim/network/websocket, both re-exported through import supranim.
For more information related to low-level UDP, TCP and WebSocket sockets, check the PowPow package on GitHub, and the PowPow API reference.