To provide a data communication system which permits a portable terminal to securely receive content data being plural pieces of packet data and which uses near radio communication.

The portable terminal device is provided with an ID reading means 41b reading packet ID and serial ID of received packet data, a reception ID broadcast means 38 emitting maximum serial ID which is read in the form of broadcast, an ID confirmation signal reception means 39 receiving maximum serial ID which is broadcast from the other portable terminal and an ID discrimination means 41d which compares maximum serial ID which the means itself reads with serial ID received by the ID confirmation signal reception means and emits the maximum serial ID which the means itself reads in the form of broadcast by the broadcast means of reception ID when serial ID that ID confirmation signal reception means receives is larger.