Do you use these for anything? If so, which ones and for what purpose? Indirectly, yes all the time. A couple of them are mirrored on Unix, Mac, BSD and Linux

Do you use these for anything? If so, which ones and for what purpose? Indirectly, yes all the time. A couple of them are mirrored on Unix, Mac, BSD and Linux to /etc/services and /etc/protocols and I use them all the time for looking up which protocol codes to use in tcpdump and firewall rules. Some stay in my memory but some are so rarely used I forget them.