The purpose of "async-io-from-scratch" (aifs) is to gain a better understanding of libraries like Boost Asio that provides tools for making asynchronous programs.
To do this, the following example implements the same echo server as implemented in Asio's C++20 examples with coroutines.
See https://github.com/chriskohlhoff/asio/blob/master/asio/src/examples/cpp20/coroutines/echo_server.cpp