Ruby on Rails server times out

I am following this tutorial:

I’m stuck here:

Run the command: ruby script\server to start the server.
Now open your browser and browse to http://127.0.0.1:3000/

I’m stuck because when I type http://127.0.0.1:3000/ in my browser, it
takes forever to open, and after several minutes it times out. I have
added the 3000 port to my exception list (tcp & udp) but with no luck.

The Webricks server is launched normally and doesn’t report any error.

Any idea?
Thanks,