Patent ID: 8023509

Claim:
A communication terminal apparatus that receives a data packet by multicast communication, the communication terminal apparatus comprising: a packet receiving section that receives a packet comprising one of a data packet and a retransmission packet as a type of the packet; a packet loss detecting section that detects whether a packet loss has occurred in a series of data packets received by the packet receiving section; a retransmission request destination selecting section that, when the packet loss detecting section detects an occurrence of the packet loss, selects a retransmission request destination IP address from one or more IP addresses contained in a distribution destination address list of the data packet received by the packet receiving section; a retransmission request packet creating section that creates a retransmission request packet that makes a request for retransmission of data of the data packet for which the packet loss occurred to the retransmission request destination IP address; a packet transmitting section that transmits the retransmission request packet to the retransmission request destination IP address; a packet check section that determines the type of the packet received by the packet receiving section; a data storing section that, when the packet check section determines the packet to be the data packet, stores data and a sequence number contained in the data packet; and a retransmission packet receiving section that, when the packet check section determines the packet to be the retransmission packet, stores data and a sequence number contained in the retransmission packet in the data storing section.