code: def _iana_unassigned_port_ranges():
      
      page = urllib2.urlopen(IANA_DOWNLOAD_URL).read()
      xml = ElementTree.fromstring(page)
      records = xml.findall('{%s}record' % IANA_NS)
      for record in records:
          description = record.find('{%s}description' % IANA_NS).text
          if description == 'Unassigned':
              numbers = record.find('{%s}number' % IANA_NS).text
              yield numbers
docs: Returns unassigned port ranges according to IANA.