Patent ID: 8559428

Claim:
A network system, comprising: a router; a first and second terminal apparatuses connected to the router; and a server coupled to and separate from the router and having a database in which a correspondence relation comprising at least an identifier of the router and an identifier of the first terminal apparatus has been registered, wherein: when the second terminal apparatus requests to communicate with the first terminal apparatus, the first terminal apparatus transmits, via the router, to the server an inquiry regarding whether the second terminal apparatus and the first terminal apparatus belong to the same group associated with the router, wherein the router transmits the identifier of the router to the server with the inquiry; the server determines whether the second terminal apparatus and the first terminal apparatus belong to the same group by checking whether an identifier of the second terminal apparatus is included in the correspondence relation, and the server allows communication between the first and second terminal apparatuses when the identifier of the second terminal apparatus is included in the correspondence relation, and denies communication between the first and second terminal apparatuses when the identifier of the second terminal apparatus is not included in the correspondence relation.