A method and apparatus for controlling communication between components connected to a bus. All equipment manufacturers may use every application available on each connected apparatus by using a unique vendor command in accordance with the IEEE-1394 standard. A controller, when accepting a target key code, calculates an application key code based on a cipher function and a target key code therefor. Then, an opening command is transmitted for the application associated with the application key code. The target apparatus, when accepting the opening command, decodes the target key code in the command. If the result of decoding is equal with the target key code of its own, an application is placed in an executable open state.