sockets
Sometimes it can be enormously instructive to work through an elementary task at a low level. Doing so might reveal that the assumptions one has been relying on are not quite as reliable or trustworthy as one had thought.
One day, while I was locked out of my car in Lake Tahoe and my friends were off skiing, I went back to basics of internet protocol client-server communication. Stephen Cleary's listening sockets blog post dispelled the fog which clouded my understanding of socket usage on the server side. The product is in my edison-sockets repository.