def connack_string(connack_code):
    """Return the string associated with a CONNACK result."""
    if connack_code == 0:
        return "Connection Accepted."
    elif connack_code == 1:
        return "Connection Refused: unacceptable protocol version."
    elif connack_code == 2:
        return "Connection Refused: identifier rejected."
    elif connack_code == 3:
        return "Connection Refused: broker unavailable."
    elif connack_code == 4:
        return "Connection Refused: bad user name or password."
    elif connack_code == 5:
        return "Connection Refused: not authorised."
    else:
        return "Connection Refused: unknown reason."