SyncServer 4.5+

SyncServer - Maintain a copy of files on another server, handy for load-sharing servers, or to have a secondary server standing by to take over in case of a crash. This utility makes an exact replica of files on a machine via the network to another machine. It was designed for load-sharing situations where all the servers need to have a copy of all the files, but can also be used for other situations, for example to publish files from a development machine to a production machine, or to have a backup server standing by that can immediately take over without first having to restore from a backup. The utility uses it's own protocol on TCP/IP port 9577 and is totally independent, you don't need things like an FTP server or Microsoft Networking (disk sharing). Traffic is one-way only, files are only sent from the master to the slave. The program uses passwords (challenge/response) to protect the access and an MD5 hash to make sure the files on the slave are exactly the same as on the master.

http://www.kessels.com/SyncServer/index.html