FTP Control Channel - TCP Port 21
All commands you send and the ftp server's responses to those commands will go over the control connection, but any data sent back (such as "ls" directory lists or actual file data in either direction) will go over the data connection.
FTP Data Channel - TCP Port 20
Used for all data sent between the client and server.
So yeah port 21 has to be accessible as well, not sure if 20 actually has to be
don't remember opening it on any firewalls before, but maybe that's why my ftp server is so terribly slow.
after a little research I figured my problem out. I'm still not sure you have to forward port 20 since it's not open on my firewall and my connection works fine, but with vsftp you do want to add
to the iptables-config file.