Venku Tur'Mukan Newbie Poster

I've recently become interested in trying to adapt my Rock-Paper-Scissors game into a multiplayer-friendly program, so today I decided I'd look up a tutorial on servers. It seems I'm following it precisely (aside from using a different IDE). However, something is going wrong and I'm not sure exactly what it is. I've looked up EOFException but it all felt like a bunch of super-behind-the-scenes mumbo jumbo that I wouldn't understand.

The tutorial

My screenshot

Could it possibly be as simple as forwarding port 7777?