To enable one application to use plural kinds of physical interfaces without discriminating a data format viewed from the application according to the kinds of the physical interfaces in use and to enable plural applications to use one physical interface irrelevantly to the kind of the physical interface.

Data transmission equipments 10A and 10B compose data, generated by adding the application ID of an application on a data reception side to a data text body, in the data format corresponding to the communication protocol of physical interfaces to be used and send the data. Data reception equipments 20A-20E decide the application ID in the received data and pass the data text body in the received data to applications corresponding to the application ID.