To run Node.js on port 80, we route port 80 to the local port the Node app is running on.
For instance, we run
sudo iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 8080
to run iptables to add a route entry to route port 80 to our Node app running on port 8080.
