IP tables are great because you can ask the OS to redirect privileged ports. This means that you can run application servers (e.g. play, spray or jetty etc.) under a less privileged account and bind to port 8080 or 9000 etc.

# Redirect port 80 to 8080.
sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080

# List redirects.
sudo iptables -t nat --line-numbers -n -L

# Delete redirect 1 (in the list above).
sudo iptables -t nat -D PREROUTING 1