Getting a Player's Server to Teleport Others to it

How would I go about making a Server System in which Players can “invade” the worlds of others (Instanced Servers).

My main goal with this system is to allow players to teleport to others’ world if they are in the same area.The problem i’m facing is very simple,I have no idea how to transport data between different servers.
I’ve heard about JobID and other applications of it but that still doesn’t solve my question of how I would go about using it with players who are near each other.