Ususally when they say "dataport" only, they're talking about the telephone jack on the side of the room phone for dialup- simply gives you a way to dial up to a local provider. If they say "internet port", usually they have provided an ethernet jack in each room that you plug right into. Lastly, some provide wireless ethernet, where you just connect from your room. The latter two always use DHCP to assign addresses.
Sometimes it's free, and others cost up to $10/night.
Just call beforehand for the details...