Uvicorn and ASGI

A Python framework does not listen on a network port by itself. A server such as Uvicorn accepts HTTP and WebSocket connections and hands each request to the app through ASGI (Asynchronous Server Gateway Interface), the async successor to WSGI, which Flask and classic Django use. Any ASGI app runs on any ASGI server, so Hypercorn, Daphne or Granian can stand in for Uvicorn.

Installed with its standard extras, Uvicorn uses uvloop and httptools for speed. In production it usually runs several worker processes, through its own --workers option or under Gunicorn, behind a reverse proxy such as Nginx.