def connect(location, timeout)

      # capture debug output in instance variable, use SSL if necessary
      uri = URI.parse(location.to_s)
      http = Net::HTTP.new(uri.host, uri.port)
      http.set_debug_output @trace
      if uri.scheme == 'https' then
        http.use_ssl = true
        http.verify_mode = OpenSSL::SSL::VERIFY_NONE
      end

      # open connection, yielding HTTP object and path to block
      begin
        response = Timeout::timeout(timeout) do
          http.start do |http|
            yield http, uri.request_uri
          end
        end
      rescue Timeout::Error
        #@dump_trace = true
        @trace << "\r\n*** Timeout::Error -- #{timeout}s ***"
        timeout *= 2
        retry
      rescue IOError
        #@dump_trace = true
        @trace << "\r\n*** IOError: #{$!} ***\r\n"
        retry
      end
      response
    end #connect()

    #---------------------------
    # Perform an HTTP POST
    # returns response
    #---------------------------
    def post(location, form_variables, timeout=@initial_timeout)
      post_data = form_variables.map do |key, value|
        CGI::escape(key.to_s) + '=' + CGI::escape(value.to_s)
      end.join('&')

      # Connect, POST, return response. Make sure to set Content-Type
      # explicitly.
      @headers['Content-Type'] = 'application/x-www-form-urlencoded'
      connect(location, timeout) do |http, path|
        http.post(path, post_data, @headers)
      end
    end # post()

    def authenticate(config)

      raise ArgumentError, 'No endpoint params specified in config', caller if config['endpoint_params'].nil?
      raise ArgumentError, 'No endpoint URI specified in config', caller if config['endpoint_uri'].nil?

      auth_params               = config['endpoint_params']
      location                  = config['endpoint_uri']
      @headers['Content-Type']  = 'application/x-www-form-urlencoded'

      response = connect(location, 5) do |http, path|
        http.post(path, auth_params, @headers)
      end

    end