And requires port forwarding, which may not be an option for people who are not on IPv4 at home (e.g. my ISP uses DS-Lite, so I cannot use IPv4 port forwarding)

And requires port forwarding, which may not be an option for people who are not on IPv4 at home (e.g. my ISP uses DS-Lite, so I cannot use IPv4 port forwarding). Bittorrent Sync works pretty good. Somebody should reverse engineer the protocol and make an open source client. Edit: why the heck is the grandparent downvoted? He/she offers a good suggestion.