It is useful mainly if you have to do some netprog in C, and secondarily if you have to deal with language bindings that do a 1:1 mapping to the BSD socket API.

It is useful mainly if you have to do some netprog in C, and secondarily if you have to deal with language bindings that do a 1:1 mapping to the BSD socket API. In other words, you will know when you need it - unless you forget it exists (note: bookmarking it might be a good idea, cause you could remember something like this exists but "what was the name again?").