Syncthing provides synchronization of a folder between a number of
collaborating devices.

To start automatic at boot make /etc/rc.d/rc.syncthing executable:
chmod +x /etc/rc.d/rc.syncthing
and add it to /etc/rc.d/rc.local
syncthing will then be started as root

Use your browser to configure syncthing: http://127.0.0.1:8080/