Old PC into USB HDD

Still though, I am hoping for something like if I just plug in a USB cable to both the old PC and the one that needs storage. And then the console/PC would recognize that old PC as a storage device. My problem is that I don't want to purchase an external enclosure, I'm wondering whether a connection between the two devices can make it work, or am I just talking about the new bi-directional USB 3.1 that's still not out in the market.