A simple solution for many is to go to control panel / uninstall a program / view installed updates (top left corner) and then delete these two updates: KB2966826 and KB2966828. Then go back to windows update / view installed updates / enable windows features and check the .net framework 3.5. Then windows update will download it without saying it cannot connect to the internet. Windows update will reinstall the two removed updates later without any ill effect.
I realize this is an older thread but I spent many hours yesterday pulling my hair out and coming up with interesting words to describe windows 8.1. I tried to use windows update, I tried enabling it in windows features only to be told it could not connect to the internet, I tried to access it in the installation dvd for hours and command prompt never found the source. Finally I saw a comment on youtube video which said to remove the two updates that were blocking it.