I have to put nodejs in port 80, but apache is already using it. How can I put both (nodejs and apache) on the same port 80? I need it because in my university all the ports
You can't. You have to run node.js on another port and then proxy requests through apache. You can do this using mod_proxy
http://davybrion.com/blog/2012/01/hosting-a-node-js-site-through-apache/