A sending-receiving system, a sender apparatus, a sending method, a receiver apparatus, a receiving method, a recording medium, and a program for improving the reliability of communication. A TS packet sequence furnished with an RTP header includes audio data. The audio data alone constitutes a TS packet sequence having the RTP header as well. That is, an RTP packet having the same sequence number of, for example, "1235h" is transmitted twice in a row. If the receiving side can receive at least one of the two RTP packets thus transmitted, that means the audio data has been sent intact. This arrangement makes it possible to prevent disconnections of audio being offered to the user. The invention applies to both the transmitting and the receiver apparatus for sending and receiving data therebetween.