Etc/services

/etc/services is a system file that details what named services run on which numeric ports.

You may find it tempting to inject information about every IANA port you know about into this file, but DON'T - some of the system daemons rely on the information in this file to run, and you may very well confuse them into inoperability if you dump tons of non-FreeBSD-related information into this file. I personally figured this out the hard way when I replaced a system's /etc/services file with one I downloaded from the 'net, and it caused natd to refuse to start until I replaced my hacked-up copy with a stock copy.