Remote File Access Without a Router

For a few weeks I had been successfully accessing my Mac mini remotely thanks to the help of this guide.

Today my router stopped working. As a fix I connected my Mac directly to the modem and am using the internal Airport card to broadcast WiFi in my apartment. I prefer this method because it means one less thing on my desk. But it broke my remote file access.

Is it possible to configure remote file access now that I am no longer using a router? Any help would be appreciated.

 

Perhaps more directly, I need to establish port forwarding on my Mac mini's internal airport.