# be root
sudo su
# note: port 13666 is for LCDd (apt-get install LCDd)
iptables -I INPUT -p tcp --dport 13666 -j ACCEPT
iptables-save
# list rules
iptables -L
# save to config
/sbin/iptables-save > /etc/iptables.conf
nano /etc/rc.local
# add this line before exit, to reload the rules in every reboot
iptables-restore < /etc/iptables.conf
shutdown -r now