drftpd error pret

[frozenwolf]

500 You need to use a client supporting PRET (PRE Transfer) to use PASV
501- ==YOU'RE BEHIND A NAT ROUTER==
501- Configure the firewall settings of your FTP client
501- to use your real IP: XXX.XXX.XXX.XXX
501- And set up port forwarding in your router.
501- Or you can just use a PRET capable client, see
501 http://drftpd.org/ for PRET capable clients

questo errore mi esce quando cerco di trasferire dei file con flashfxp come sistemo?