Allow two servers to transfer entities to eachother

Devise a system whereby two servers can transfer entities to each others. From the client's point of view this would appear as being teleported into a new world.
The entities are serialized to Atlas and sent from one server to another.
Any child entity must also be sent along, and any entity reference updated (as the entities will have their id changed).

For detection, a crude system where each server's peers are coded in a configuration file will initially suffice.
A protocol needs to be specified for the server-to-server communication.