FarCry 4 does not work that way
Pc has its own API called windows .. PS4 does not use WINDOWS it has a different API (not direct X 11\MS windows )
plus there are no games that are cross platform co op compatible the way your describing that i know if even out yet
Plus PS4 uses its own network ( the playstation network )
as does X box (x box live network )
that is separate then what a PC uses (the internet and uplay) for establishing a network connection
also the files in the game would not match up as PC has a different Texture pak that what was used in the console version (\pc looks better and has more options for adjusting the video settings )
so if you want to play with your friends on a console you need to have the game \ and the same console\ on the same network , they have for it to connect