I wrote a rudimentary HTTP server and practiced writing it for the past few days. I used Screenflow to record and replayed it in fast motion so I can see what I was doing. Going through it several times, you make a lot of mistakes and see pretty much every variation of errors you would encounter for that project. I learned a lot and kept my code to the bare minimum. You can see the code on github

It uses Cucumber to set up the expected behavior. Then I jump into RSpec to start implementing the guts. When all the RSpec tests pass, I check on Cucumber again to see if I was able to accomplish my goal. The server only handles one request, but you can keep modifying it to make it more robust and add more features.