Peer-to-Peer Synchronization of Multiple Computers

Is it possible with any version of SyncBack to connect and synchronize multiple non-connected computers in a peer-to-peer type of environment, without using cloud-based services?

OR

Is there another method that I can synchronize my 3 computers, 2 External HD's and my 128GB USB Drive, without needing to do them individually, so that they all have the same information on them and also without using cloud-based services?

Thank You.