> Trying to get two file servers set up between two locations - both on
> residential connections, so no static IPs.  Want to have them
> synchronize back and forth.
>


One way to do that is to use an RVP (Rendez vous point; think skype,  
etc) between the two hosts with dynamic IPs. We implemented such a  
scheme
with our peer to peer file sharing scheme a few years ago (combined  
with NAT whole punching). What you are trying to do is
bidirectional file replication with dynamic IPs. I am assuming that  
you don't care about concurrent writes to the files (because unless you
have a distributed lock manager in addition to the RVP, the content of  
the files will not be deterministic).

A. A. El Haddi,
EnduraData