Inspired by this question I came up with this weird idea of making what that user actually wants to prevent. So, bear with me for a little bit:
Let's assume that for some reason we could make the traffic sent from a specific application to another to travel to a router/routing device because the source device cannot determine on its own where does it have to send the packet. This means, even names like "localhost" or IPs like 127.0.0.1 does not work for this source device, but it rather has to send everything to another device to send the information its "destination" device (which, we know, it's that same server).
So, simplifying and making it an actual question: is there any way, remotely as it could be, to hijack routing tables/loopback interfaces/whatever it takes to make a machine send it's traffic out when those communications are supposed to be internal?
Think in how many web server do have their databases in there and send "internal" requests for connection with data... TCP services... and how firewalls are configured to block weird traffic in but not so much for traffic out. This made me tick and come and ask this weird question.