Abstract: A low cost communication apparatus enables detection of an apparatus present on a different network in a router multistage network having a plurality of routers. When a communication apparatus cannot detect, on a network thereof, a desired apparatus, the communication apparatus requests a connection support server securing communication paths with all the apparatuses on a home network, to relay an apparatus detection request. The connection support server transfers the request to relay the apparatus detection request, to an arbitrary apparatus belonging to a different network from the network to which the communication apparatus belongs, and the arbitrary apparatus, by proxy, performs an apparatus detection, and transfers information about a detected apparatus to the connection support server. By obtaining the information from the connection support server, the communication apparatus detects the apparatus on the different network.

Abstract: The present invention improves the reliability and safety of communication in a communications system wherein communication is relayed. When an on-premise terminal 100 sets relay information, such as NAT information or the setting information of a packet filter, in a gateway 110, the relay information is set after confirming whether the NAT information for which a setting attempt is being made duplicates the NAT information of another on-premise terminal 101. The same applies to the case of deleting relay information. If the NAT information is duplicate, then interference with the communication of the other on-premise terminal 101 is prevented by modifying the relay information for which a setting attempt is being made, specifically the port number of the gateway 110 on a global network 001.

Abstract: A communication apparatus (10) transmits to a server (001) three address information, check requests 1 to 3 whose destination port numbers are set to be [SP1] and whose source port numbers are set to be respective [LP1] to [LP3] different from each other. The communication apparatus (10) also transmits a P2P communication preparation packet whose source port number is set to be one of [LP1] to [LP3], to a destination different from the server (001), between the address information check requests 1 and 3. The communication apparatus (10) determines the NAT characteristic of a router (101) based on port numbers [GP11], [GP12] and [GP14] of the router (101) notified of by address information check responses 1 to 3.

Abstract: Provided is a communication terminal capable of establishing a P2P communication path with a communication terminal connected to a different private network. A communication terminal (10) transmits and receives messages to and from a server (30) via a router (11), thereby examining a relay characteristic of the router (11). When the examined relay characteristic of the router (11) is Port Reuse, the communication terminal (10) determines address information, which contains at least a port number of the communication terminal (10), which port number is to be used for P2P communication with a communication terminal (20), to be address information about the router. The communication terminal (10) exchanges the determined address information about the router (11) with the communication terminal (20). Based on the exchanged address information, the communication terminal (10) establishes a P2P communication path with a communication terminal (20).

Abstract: The NAT type of a router can be examined by communicating with one server having one IP address, and a P2P communication path is established efficiently using the NAT type obtained by the examination. A terminal 100 transmits a plurality of port number examination request packets having a plurality of port numbers of a server 001 set as the destination port. The terminal 100 refers to a port number examination response packet received from the server 001 to acquire a plurality of port numbers obtained by address translation by a router 101 for the port number examination request packets respectively. The terminal 100 determines the NAT type of the router 101 based on the acquired translated port numbers. The terminals 100 and 200 establish a P2P communication path efficiently using the determined NAT type.

Abstract: To provide, without requiring a user to have special knowledge or to pay a high cost, a communication apparatus which enables detection of an apparatus present on a different network in a router multistage network comprising a plurality of routers. When a communication apparatus (101) cannot detect, on a network thereof, a desired apparatus, the communication apparatus requests a connection support server (001) securing communication paths with all the apparatuses on a home network, to relay an apparatus detection request. The connection support server (001) transfers the request to relay the apparatus detection request, to an arbitrary apparatus belonging to a different network from the network to which the communication apparatus (101) belongs, and the arbitrary apparatus, by proxy, performs an apparatus detection, and transfers information about a detected apparatus to the connection support server (001).

Abstract: Provided is a communication terminal capable of establishing a P2P communication path with a communication terminal connected to a different private network. A communication terminal (10) transmits and receives messages to and from a server (30) via a router (11), thereby examining a relay characteristic of the router (11). When the examined relay characteristic of the router (11) is Port Reuse, the communication terminal (10) determines address information, which contains at least a port number of the communication terminal (10), which port number is to be used for P2P communication with a communication terminal (20), to be address information about the router. The communication terminal (10) exchanges the determined address information about the router (11) with the communication terminal (20). Based on the exchanged address information, the communication terminal (10) establishes a P2P communication path with a communication terminal (20).

Abstract: The present invention improves the reliability and safety of communication in a communications system wherein communication is relayed. When an on-premise terminal 100 sets relay information, such as NAT information or the setting information of a packet filter, in a gateway 110, the relay information is set after confirming whether the NAT information for which a setting attempt is being made duplicates the NAT information of another on-premise terminal 101. The same applies to the case of deleting relay information. If the NAT information is duplicate, then interference with the communication of the other on-premise terminal 101 is prevented by modifying the relay information for which a setting attempt is being made, specifically the port number of the gateway 110 on a global network 001.

Abstract: The NAT type of a router can be examined by communicating with one server having one IP address, and a P2P communication path is established efficiently using the NAT type obtained by the examination. A terminal 100 transmits a plurality of port number examination request packets having a plurality of port numbers of a server 001 set as the destination port. The terminal 100 refers to a port number examination response packet received from the server 001 to acquire a plurality of port numbers obtained by address translation by a router 101 for the port number examination request packets respectively. The terminal 100 determines the NAT type of the router 101 based on the acquired translated port numbers. The terminals 100 and 200 establish a P2P communication path efficiently using the determined NAT type.