Are you getting anything if you visit port 80 and /api/discovery.xml? If not you will need to forward port 80 to the port the open-hab webserver runs on. Ive done it with this iptables command:
iptables -t nat -A PREROUTING -p tcp -d 192.168.1.6 --dport 80 -j DNAT --to-destination 192.168.1.2:8080
Openhab is listning to 192.168.1.2:8080, and since I have apache configured on port 80 on that IP I added a new IP, and forward port 80 on that to the openhab server:
ifconfig eth0:0 192.168.1.6