To easily judge whether communications can be directly established or not between radio terminal devices.

The first radio terminal device 102 transmits ICMP_echo_request signals directly to a second radio terminal device 103 after the first radio terminal device 102 is transferred to a DLP mode. When the first radio terminal device 102 receives ICMP_echo_reply signals as a reply from the second radio terminal device 103 within a certain time, the number of replies received is counted up, and on the other hand, when the first radio terminal device 102 receives no ICMP_echo_reply signal from the second radio terminal device 103 within a certain time, the number of no replies is counted up, whereby it can be easily judged whether the first radio terminal device 102 is capable of establishing communications directly with the second radio terminal device 103 in a DLP mode.