Passive and Active FTP
February 28th, 2010I’ve been having some active/passive FTP issues recently. It seems the server had some specific issues with FileZilla (an awesome free, open source FTP client– highly recommended).
From FileZilla’s Wiki:
Setting up FileZilla Client
In case you’re running FileZilla 3, it’s recommended you run the network configuration wizard. It will guide you through the necessary steps and can test your configuration in the end.
Obviously, if you want to connect to any server, you need to tell your firewall that FileZilla should be allowed to open connections to other servers. Most normal FTP servers use port 21, SFTP servers use port 22 and FTP over SSL/TLS (implicit mode) use port 990 by default. These ports are not mandatory though, so it’s best to allow outgoing connections to arbitrary remote ports.
Since there are many servers on the internet that are misconfigured and don’t support both transfer modes, it’s recommended that you configure both transfer modes on your end.
[edit] Passive modeThe client has no control over what port the server chooses for the data connection in passive mode, so in order to use passive mode, you’ll have to allow outgoing connections to all ports in your firewall.
[edit] Active modeIn active mode, the client opens a socket and waits for the server to establish the transfer connection.
By default, FileZilla Client asks the operating system for the machine’s IP address and for a free port number. This configuration can only work if you are connected to the internet directly without any NAT router and if you have set your firewall to allow incoming connections on all ports greater than 1024.
If you have a NAT router, you need to tell FileZilla your external IP address or active mode connections will not work with servers outside your local network:
* If you have a fixed external IP address, you can enter it in the configuration dialog of FileZilla.
* If you have a dynamic IP address, you can let FileZilla obtain your external IP address from a special website automatically each time you start FileZilla. No matter what version of FileZilla you have, no information will be submitted to that website.If in doubt, use the second option.

