Abstract: A network system includes at least one computer which includes a processor for processing data and attaching an associated contents code corresponding to the processed data and data group information indicative of a data group corresponding to the attributes of the processed data to ask a data transmission request and a transmission controller connected to the processor for controllably transmitting a frame including the transmission sub-network, the contents code and the processed data to the first sub-network according to the data group information of the processed data. A second computer connected judges whether or not the contents code of the frame received from the first sub-network conforms to one of a plurality of data reception enable/disable judgement conditions.

Abstract: A communication system and communication method having protocols used are to priorly process real-time data without delay. Information of a protocol header of data to be sent or received is used as priority decision information to decide whether or not the data should be priorly send- or receive-processed. The information to be priorly processed of combination of the priority decision information is registered and managed as priority data information before being stored. The data send or receive process fetches the priority decision information from the send or receive data before deciding whether or not the data are registered as the priority data information. If so, the data are send- or receive-processed prior to the data that are not registered.