I'm having problems settig up my application using Thin and Sinatra. I have created a development-config.ru file that contains the following settings: # This is a rack configuration file to fire up the Sinatra application. # This allows better control and configuration as we are using the modular # approach here for controlling our application. # # Extend the Ruby load path with the root of the API and the lib folder # so that we can automatically include all our own custom classes. This makes # the requiring of files a bit cleaner and easier to maintain. # This is basically what rails does as well. # We also store the root of the API in the ENV settings to ensure we have # always access to the root of the API when building paths. ENV['API_ROOT'] = File.dirname(__FILE__) $:.unshift ENV['API_ROOT'] $:.unshift File.expand_path(File.join(ENV['API_ROOT'], 'lib')) $:.unshift File.expand_path(File.join(ENV['API_ROOT'], 'db')) # Now we can require all the gems used for the entire API by simpling requiring # them here. We can also include the classes that we have defined inside the lib # folder. require 'rubygems' require 'bundler' # Run Bundler to setup our gems properly. This will install all the missing gems on # the system and ensure that the deployment environment is ready to run. Bundler.require # To make the loading easier for the application, we will now automatically load all # models that have been defined inside the lib folder. This ensures that we do not need # to load them anymore anywhere else in our application, as the models will be known to # ruby everywhere. Dir.glob(File.join(ENV['API_ROOT'], 'lib', '**', '*.rb')).each{|file| require file} # Now we will configure the Sinatra application so that we can fire up the entire API. # This requires some detailed settings like whether logging is allowed, the port to be # used and some folder locations. require 'sinatra' require 'app' set :logging, true set :dump_errors, true set :port, 3001 set :views, "#{ENV['API_ROOT']}/views" set :public_folder, "#{ENV['API_ROOT']}/public" set :environment, :test # Start up the Sinatra application with all the settings that we have defined. run App.new This is based upon the information I found on the Sinatra website. However, the problem is that I cannot get the application running on port 3001. If I use thin start -R development-config.ru it runs on port 3000. If I use rackup config-development.ru it runs on port 9696. However I never see Sinatra kick in or run over port 3000. My application looks like this: # Author : Arne De Herdt # Email : # This is the actuall application that will be running under Sinatra # to serve the requests for the billing middleware API. # We use the modular approach here to allow control when deploying # the application using Capistrano. require 'sinatra/base' require 'logger' require 'savon' require 'billcrux' class App < Sinatra::Base # This action responds to POST requests on the URI '/billcrux/register' # and is responsible for handeling registration requests with the # BillCrux payment system. # The post "/billcrux/register" do # do stuff end end Can someone tell me what I am doing wrong?