The FTP protocol defines two ways of transferring data. “Passive mode” means that the server will be “passive” and accept data connections from the client, instead of requiring the client be able to accept connections back from the server. (This unusual behavior of server-to-client connections is unique to the FTP protocol.)
Almost all modern network client environments only permit outbound connection requests, for security reasons. This requires the use of passive mode for a successful FTP transfer, as it will be impossible for the server to establish a connection to the client.
In particular, Transmit running on any computer behind a firewall or NAT will not be able to transfer data to or from an FTP server unless passive mode is used.
The issue can be avoided entirely by using any transfer protocol other than FTP, such as SFTP.
In the unlikely event that you need to disable passive mode, there are two ways to do it.
To disable passive mode for all FTP connections:
- Choose Transmit > Preferences…
- Click Transfers
- Uncheck Use passive (PASV) mode for transfers
To disable passive mode for an individual favorite:
- Edit the favorite using the favorites editor
- Uncheck Use passive mode