TCP client and multithreaded server in 14 lines of Ruby code: https://gist.github.com/TeWu/1234573/52bbbc91b4cd98343b728a9c56f569bad6f68f76
Building a simple websockets server from scratch in Ruby: https://www.honeybadger.io/blog/building-a-simple-websockets-server-from-scratch-in-ruby/
Keep alive without content-length (via transfer-encoding: chunked): https://stackoverflow.com/questions/49256096/are-http-keep-alive-connections-possible-without-content-length-headers
Building a HTTP server from scratch using Ruby: https://arnabsen.rocks/posts/building_server_from_scratch/#2-parsing-the-http-request