I'm carrying out a tutorial to implement NTLM authentication inside a ruby website => Tutorial

Within this tutorial the say to create a "Private method submitted_user extracts Home windows username from HTTP header" I'm attempting to access this http header but i am unable to work out how. I attempted:

url = URI.parse('http://my.website...')
req = Net::HTTP::Get.new('http://my.website....')
@res = Net::HTTP.start(url.host, url.port) {|http|
  http.request(req)
}

I quickly obtain the http header of my server not from the client, this really is off beam logic since it is server side code. I really hope someone might help and sorry if this sounds like a stupid question!