check.rb

require 'net/http'

def get_response(url)
  uri = URI.parse(url)
  path = (uri.path.empty?) ? '/' : uri.path

  request = Net::HTTP.new(uri.hostname, uri.port)
  request.request_head(path)
end

def is_site_up?(url)
  response = get_response(urL)
  ["200", "302"].include? response.code
end

p is_site_up? "http://stackoverflow.com"
#=> false

p is_site_up? "http://www.business.uconn.edu"
#=> true