By SFTP are you looking for encryption? SFTP is ftp over SSH. So, you can look for a SSH daemon (there are some freeware on the internet) to install on the server and SSH clients on the client side. Some ftp clients (e.g. WRQ Reflection) also support SSH, but you need to configure its use. FTP servers run on port 20 and 21 and SSH servers run on port 22 so they can co-exist on one server.