The outlet behind your couch and the outlet behind your router terminate at the same busbar in your breaker panel. That shared copper is the entire trick behind powerline networking. Two adapters turn any pair of outlets into the endpoints of a wired link, with no drilling, no fishing cable through insulation, and no cord stapled along a baseboard. I went this route for a smart TV stranded in my three-season room, where the nearest network jack sat more than 30 feet away through finished walls. I used the TP-Link AV1000 powerline adapter, and it worked. Not every outlet performs the same, though, and the reasons trace back to decisions your electrician made before the drywall went up.