Since WP All Import only supports fetching data files over HTTP or HTTPS, many users employ their own proxy script in PHP to act as an intermediary. This script would read the data file from the FTP server and output it over HTTP (for consumption by WP All Import).
For example, you could have a PHP script on your server called ftp-proxy.php and then tell WP All Import to import from that URL:
http://example.com/ftp-proxy.php
Security note: Anyone could access your data if they guess this URL.We recommend either removing this file from the server after you've run your import or renaming this file to something "unguessable" (e.g. 'ftp-proxy-24dxfi3.php') but understand that method is not perfectly secure. For best security use an .htaccess rule allowing access only from localhost.