docs: def port_type(arg):
  	"""An argparse type representing a tcp or udp port number."""
  	error_msg = "{0} is not a valid port".format(repr(arg))
  	try:
  		arg = ast.literal_eval(arg)
  	except ValueError:
  		raise argparse.ArgumentTypeError(error_msg)
  	if arg < 0 or arg > 65535:
  		raise argparse.ArgumentTypeError(error_msg)
  	return arg