NETWORK COMMUNICATION MONITORING SYSTEM, NETWORK COMMUNICATION MONITORING METHOD, CENTRAL APPARATUS, RELAY UNIT, AND MEMORY PRODUCT FOR STORING A COMPUTER PROGRAM

The central apparatus obtains the destination information of a plurality of terminal devices, generates one request packet consolidating the obtained plural destination information, and transmits the generated one request packet. The relay unit receives one request packet, generates a plurality of request packets on the basis of the consolidated destination information, and transmits the generated request packet. The relay unit receives reply packets from a plurality of terminal devices, generates one reply packet consolidating the destination information of the transmission origins of the received plural reply packets, and transmits them to the central apparatus. The central apparatus receives the returned one reply packet and determines continuation and blockade of the network connection for each terminal device.