Depending on the level of your students, if you get the chance to talk a little bit about sockets, you can always guide them to build a very simple HTTP Server.
In reality, you don't need to go much deep on sockets, just talk about send() and recv(), and in very simplistic terms. You can check this [1] blog post of mine, and the final code is very simple but very useful to learn how the "internet" works..
Good luck!