my apple tv doesn't connect automatically to iTunes unless i turn on iTunes on computer

Hello I have two apple tv's 3rd gen. the problem i am having is any time i want to access my movie library it tells me to turn on home sharing in which i already have home sharing turned on. I have noticed for me to access my movies i have to go upstaires and open up itunes on my computer to access the movies. on my computer i have it set to wake when there is network activity i.e. when the apple tv is trying to access my itunes library. how do i fix this so i dont physically have to go turn on computer and open up itunes?