IIRC, 580EXII has a PC sync socket, so that means you can use any PC cord.
To connect a PC cord to the Skyport, you'll need an adapter. $20 available at Cathay Photo. 'Made' by PW. These flimsy and delicate adapters are known to fail. Best is to hardwire a 3.5mm monoplug directly to a short PC sync cable for much better reliability. And it costs faaaaar less than the crappy adapters.