Did you cancel or otherwise interrupt a print? If so and you didn't do it exactly right, the "can't open port" is the usual result.
Since it was working and now, without any apparent change of anything, it's not, I doubt your network software has changed.
Since the ethernet plugs directly into the printer, unplug the ethernet cable and the printer, don't merely power it off, unplug it. Power off your computer, don't simply restart it, turn it off. Plug everything back in. restart the computer and power on the printer. See if that doesn't change things.