OK, I've solved by myself.
There were additional iptables commands to do.
I've found these here:
http://lists.prato.linux.it/pipermai...er/006954.html
Practically, to open port 4662, as root, the commands to do are:
iptables -I INPUT 1 -p tcp --dport 4662 -j ACCEPT
iptables -I INPUT 1 -p udp --dport 4662 -j ACCEPT
iptables -I OUTPUT 1 -p tcp --sport 4662 -j ACCEPT
iptables -I OUTPUT 1 -p udp --sport 4662 -j ACCEPT
I hope it helps.
Thank you anyway.
TheHighwayman