A network control system which transmits mass data efficiently, speedily, and reliably, and which includes a controller that can easily decide what a target has transmitted. The controller and the target are used in this network control system. The network control system includes the a controller for transmitting a message, the target for performing processing according to the message, and an initiator for establishing a connection for data transmission between the controller and the target, and the system performs data transmission by using plural protocols. Either or both of the controller and the target is/are present in a device, and the target is constructed so as to receive a message by a first one of the plural protocols and to transmit data onto the connection by a second one of the plural protocols according to the received message.