How to make local port mappings with iptables
Following should work
iptables -t nat -A PREROUTING -p tcp -d <your-ip> --dport 80 -j DNAT --to-destination <your-ip>:8080
Following should work
iptables -t nat -A PREROUTING -p tcp -d <your-ip> --dport 80 -j DNAT --to-destination <your-ip>:8080