Depending on the implementation, but most probably it would burn the coils ("transformer") in the port, and probably the whole port module around, since the ene

Depending on the implementation, but most probably it would burn the coils ("transformer") in the port, and probably the whole port module around, since the energies are high enough to burn quite a large chunk of material. Cables are a lot thicker than the electronics inside the port itself, so my bet would be, port goes first, probably fails in a way that disconnects the current, if not, the ethernet cable would probably compete with the circut breaker on who melts first (circut breakers, even if they're marked with (eg.) 20A on them, survive a much higher current for a short time, before they eventually fail, due to some electronics, especially motors and large lightbulbs act almost like a short circut when they're starting up).