Can FileTransfer be used to target remote FTP servers? I need to send files to a remote server within an ajax callback.
Snooping around Drupal's includes, I came across the FileTransfer class, but I haven't fully understood the concept of its access limit to $jail (defaults to Drupal's root).
Is it possible to use this class to access remote FTP directories as well?
If so, how?
What used for the $jail parameter is the directory for which the operations are limited; if you try deleting a file outside that directory, the operation is not allowed.

If you want FTP access to a directory on a remote site, you should use the FileTransferFTP class, and create an instance with FileTransferFTP::factory().