Using Passive (PASV) or Active (PORT) FTP Mode
How FTP Works
FTP works by opening two different connections between your FTP program (also
called an FTP Client) and the FTP Server (FTP site you are trying to connect to).
These connections are opened on what is called ports. A port is like a
passageway for data to flow between two computers. The first connection opened
is on Port 21, which is the standard FTP port and is the Command connection.
This is the port where commands are send from your computer to the FTP server to
tell it what you want to do, be it listing a directory, moving to another one,
deleting a file, uploading or downloading a file, or changing file permissions,
etc. You probably have seen these commands pop up in the message area of your
FTP program, like RETR, CWD, and LIST for example. The second connection is where
the actual data (like a file) is transferred between your computer and the server.
Now the port that the transfer takes place on depends on whether you have your
FTP program set to Passive mode or Active mode.
When your FTP program is in Passive mode, it opens a data communications port
between your computer and the server on port 21 by using a PASV command. Then
the server will respond back telling your FTP program what IP address and port
to connect to for the actual transfer of data. Your FTP program will then connect
to that IP address and port, and the transfer of the file will start. If you are
using a corporate firewall or even a personal firewall such as ZoneAlarm or the
firewall in Windows XP, these should be able to let you use Passive mode. This
is because most firewalls will see this data transmission as outbound traffic
and normally should not attempt to block it. If for some reason you are having
problems with Passive mode, such as the directory listing hanging or stalling
during data transfers, you can always try Active mode.
Active mode works the opposite direction of Passive mode in that instead of the
server determining the IP address and port to connect to, your FTP program will
give this information to the FTP server. So when data transmission is requested,
your FTP program will issue a PORT command and the IP address and port number it
wants to use for the data connection. The FTP server will then connect directly
to your FTP program on that IP address and port and data transfer will start. If
the FTP server is behind a firewall (as is Active Web Hosting's FTP server),
then this is the mode you should use.
Which mode should I use?
Because Active Web Hosting's server is behind a firewall, it's recommended that
you have your FTP program set to Active mode. However, if you are having
problems with this connection, you may try Passive mode. You might see messages
in your FTP client from the server recommending "PASV" or Passive mode. You
shouldn't need to change to this mode though unless you are experiencing