Showing ftp server error:21

showing ftp server error while i m trying to install or uninstall some thing after that it shwoing me like this

have a look on screenshot

Cloudflare doesn’t proxy FTP, so that would break installations that rely on an FTP connection to your web domain.

Wordpress only falls back to FTP if it can’t install updates internally. You should fix this process rather than fall back to FTP: