The command ftpsync is a tool allowing incremental and recursive FTP transfer from a local directory to a remote FTP-served directory.
We sometimes need to mirror a set of files on a remote ftp server. The perfect tool (rsync) is not always available.
Developing a script invoking a standard FTP client software will cause useless transfers (all files again and again even if they have not changed), and taking sub-directories into account will not be easy.
ftpsync is the adequate tool because it reduces the amount of data transferred by not transferring a given local file if the remote copy has an newer date (so the copy is already done and up to date) and the same size (transfer completely done). The difference between system clocks is taken into account using the ftp protocol. ftpsync is somewhat "like" the rsync command but it uses the FTP protocol and only transfers local files to a remote FTP server. Moreover it implements the missing 'recursive PUT' FTP command.