code: def with_port_scanning(cls):
    
  
    def init(wsgi_app, flags):
      # base_port: what's the first port to which we should try to bind?
      # should_scan: if that fails, shall we try additional ports?
      # max_attempts: how many ports shall we try?
      should_scan = flags.port is None
      base_port = core_plugin.DEFAULT_PORT if flags.port is None else flags.port
      max_attempts = 10 if should_scan else 1
  
      if base_port > 0xFFFF:
        raise TensorBoardServerException(
            'TensorBoard cannot bind to port %d > %d' % (base_port, 0xFFFF)
        )
      max_attempts = 10 if should_scan else 1
      base_port = min(base_port + max_attempts, 0x10000) - max_attempts
  
      for port in xrange(base_port, base_port + max_attempts):
        subflags = argparse.Namespace(**vars(flags))
        subflags.port = port
        try:
          return cls(wsgi_app=wsgi_app, flags=subflags)
        except TensorBoardPortInUseError:
          if not should_scan:
            raise
      # All attempts failed to bind.
      raise TensorBoardServerException(
          'TensorBoard could not bind to any port around %s '
          '(tried %d times)'
          % (base_port, max_attempts))
  
    return init
docs: Create a server factory that performs port scanning.
  
    This function returns a callable whose signature matches the
    specification of `TensorBoardServer.__init__`, using `cls` as an
    underlying implementation. It passes through `flags` unchanged except
    in the case that `flags.port is None`, in which case it repeatedly
    instantiates the underlying server with new port suggestions.
  
    Args:
      cls: A valid implementation of `TensorBoardServer`. This class's
        initializer should raise a `TensorBoardPortInUseError` upon
        failing to bind to a port when it is expected that binding to
        another nearby port might succeed.
  
        The initializer for `cls` will only ever be invoked with `flags`
        such that `flags.port is not None`.
  
    Returns:
      A function that implements the `__init__` contract of
      `TensorBoardServer`.