PassiveMode
(boolean) Use passive/firewall mode when accessing the file. Passive mode (also known as "firewall mode") is required whenever you need to transfer files to or from an FTP server from behind a firewall. Passing the default value true enables passive mode and passing false disables it.
Normally, your computer makes a connection to an FTP server, and the FTP server responds by opening a connection back to your computer. This return connection won't work if your computer can't be reached directly from the Internet. In passive mode, both connections are made from your computer, so the FTP server doesn't have to do any connecting-it just waits passively for your computer to make both of the connections to it.
Most servers support passive mode connections, so it's generally best to leave this setting enabled.