uninitialized constant Rails::Server (NameError)

Currently while trying to set up my ruby files, i am running into this problem. Im not sure what the problem is, as Rails is correctly installed. I am mostly new to Rails/Ruby, and am picking up rails. I haven't seen this problem else where.

I am working on windows 10, all gems are installed, and rails is installed. Im am running this in RubyMine.

Here is the line where the error is thrown:

config.action_mailer.asset_host = 'http://localhost:' + Rails::Server.new.options[:Port].to_s

Here is an image of the console Console