code: def _find_listeners():
      
      for i in range(31):
          try:
              if gpib.listener(BOARD, i) and gpib.ask(BOARD, 1) != i:
                  yield i
          except gpib.GpibError as e:
              logger.debug("GPIB error in _find_listeners(): %s", repr(e))
docs: Find GPIB listeners.