Patent ID: 7949703

Claim:
A client device for joining a group by registering with a server that belongs to the group, the group being a range within which contents are available, the client device including a processor comprising: a judging unit that judges whether a total number of groups that the client device is currently registered to be in is less than a maximum number of groups that the client device is permitted to be in, when the client device attempts to join the group to be connected to the server, wherein the judging unit selects a server from among a plurality of servers belonging to the group based on at least one of a set of predetermined conditions including a distance to the client device, a time period taken to communicate with the client device, a performance capability and a processing state of each server; a communicating unit that (i) transmits to the server information unique to the client device, and receives from the server identification information identifying the group to which the server belongs when the total number of groups is less than the maximum number of groups that the client device is permitted to be in, and (ii) prevents transmission of the unique information to the server when the total number of groups is equal to or greater than the maximum number of groups; and a registering unit that registers the received identification information in the client device, wherein the registering unit monitors expiration of a valid period and deletes the identification information upon the expiration of the valid period.