Patent ID: 8611342

Claim:
A receiving apparatus comprising: a communication interface configured to receive a check packet transmitted from a transmitting apparatus using Transfer Control Protocol (TCP), the check packet including a random number that is different from random numbers included in other check packets transmitted from the transmitting apparatus; circuitry configured to: generate a TCP acknowledgment message to the check packet, the TCP acknowledgment message including acknowledgment information based on shared data shared with the transmitting apparatus; and control the communication interface to transmit the TCP acknowledgment message to the transmitting apparatus; and a display configured to display data received from the transmitting apparatus, wherein the transmitting apparatus computes expected acknowledgment information based on the shared data shared with the receiving apparatus, produces a comparison result for the receiving apparatus based on the acknowledgment information and the expected acknowledgment information, counts a time elapsed from transmitting the check packet, and prohibits transmission of data to the receiving apparatus when the comparison result indicates that acknowledgment information and the expected acknowledgment information do not match or a predetermined time elapsed from transmitting the check packet expires before the acknowledgment message is received.