do_rpc

# File lib/xmlrpc/client.rb, line 463
    def do_rpc(request, async=false)
      header = {
       "User-Agent"     =>  USER_AGENT,
       "Content-Type"   => "text/xml; charset=utf-8",
       "Content-Length" => request.bytesize.to_s,
       "Connection"     => (async ? "close" : "keep-alive")
      }

      header["Cookie"] = @cookie        if @cookie
      header.update(@http_header_extra) if @http_header_extra

      if @auth != nil
        # add authorization header
        header["Authorization"] = @auth
      end

      resp = nil
      @http_last_response = nil

      if async
        # use a new HTTP object for each call
        http = dup_net_http

        # post request
        http.start {
          resp = http.request_post(@path, request, header)
        }
      else
        # reuse the HTTP object for each call => connection alive is possible
        # we must start connection explicitly first time so that http.request
        # does not assume that we don't want keepalive
        @http.start if not @http.started?

        # post request
        resp = @http.request_post(@path, request, header)
      end

      @http_last_response = resp

      data = resp.body

      if resp.code == "401"
        # Authorization Required
        raise "Authorization failed.\nHTTP-Error: #{resp.code} #{resp.message}"
      elsif resp.code[0,1] != "2"
        raise "HTTP-Error: #{resp.code} #{resp.message}"
      end

      # assume text/xml on instances where Content-Type header is not set
      ct_expected = resp["Content-Type"] || 'text/xml'
      ct = parse_content_type(ct_expected).first
      if ct != "text/xml"
        if ct == "text/html"
          raise "Wrong content-type (received '#{ct}' but expected 'text/xml'): \n#{data}"
        else
          raise "Wrong content-type (received '#{ct}' but expected 'text/xml')"
        end
      end

      expected = resp["Content-Length"] || "<unknown>"
      if data.nil? or data.bytesize == 0
        raise "Wrong size. Was #{data.bytesize}, should be #{expected}"
      end

      parse_set_cookies(resp.get_fields("Set-Cookie"))

      return data
    end