To enable the FTP server on OS X, you have to load the FTP service like this:
sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist
To stop the service you need to unload the service with the same command:
sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist
But this only works for admin account users. How to enable standard account ?