AIOHTTP

Kestrel is a cross-platform web server for ASP.NET Core. Kestrel is the web server that's included and enabled by default in ASP.NET Core project templates. Kestrel supports HTTPS, HTTP/2 (except on macOS), Opaque upgrade used to enable WebSockets, Unix sockets for high performance behind Nginx. Kestrel is supported on all platforms and versions that .NET Core supports. Some browsers require granting explicit permission to trust the local development certificate. Project templates configure apps to run on HTTPS by default and include HTTPS redirection and HSTS support. The Kestrel web server has constraint configuration options that are especially useful in Internet-facing deployments. There's a separate limit for connections that have been upgraded from HTTP or HTTPS to another protocol (for example, on a WebSockets request). The default maximum request body size is 30,000,000 bytes, which is approximately 28.6 MB.

Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user. Tornado is different from most Python web frameworks. It is not based on WSGI, and it is typically run with only one thread per process. While some support of WSGI is available in the tornado.wsgi module, it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe. Tornado is integrated with the standard library asyncio module and shares the same event loop (by default since Tornado 5.0). In general, libraries designed for use with asyncio can be mixed freely with Tornado.