Relay method, relay system, and relay program

1. A relay method performed by a relay system that relays communication between (i) a target terminal within a closed network and having a private address and (ii) a client terminal not within the closed network, the relay system including a first relay apparatus, a second relay apparatus that is connected to the target terminal, and a connection management apparatus for managing a connection at the time of relaying the communication between the client terminal and the target terminal, the method comprising:

acquiring from the client terminal a first connection request including a terminal identification information for identifying the target terminal;

the connection management apparatus, responsive to the acquiring the first connection request, specifying a connecting information indicating one port number selected from among a plurality of port numbers of the first relay apparatus for relaying the communication between the client terminal and the target terminal;

the connection management apparatus storing the connecting information and the terminal identification information in a storage in association with each other;

the connection management apparatus notifying the client terminal about the specified connecting information; and

the first relay apparatus, responsive to receiving a second connection request for communicating with the target terminal, addressed to the one port number indicated by the connecting information from the client terminal, relaying communication between the client terminal and the target terminal on the basis of the terminal identification information associated with the connecting information in the storage, wherein said relaying comprises specifying the second relay apparatus to which the target terminal is connected on the basis of the terminal identification information stored in the storage, and relaying communication between the client terminal and the target terminal via the specified second relay apparatus.

2. The relay method according to claim 1 , wherein

the relay system includes a plurality of first relay apparatuses and a plurality of second relay apparatuses and the plurality of first relay apparatuses and the plurality of second relay apparatuses constitute a mobile network, and the target terminal is connected to the mobile network,

the target terminal is assigned a private address enabling access in the mobile network, and

in the relaying, the first relay apparatus relays communication between the client terminal and the target terminal by communicating with the target terminal on the basis of the private address of the target terminal.

3. The relay method according to claim 1 , wherein

in the storing, the relay system further stores a port number of the target terminal used for communication with the target terminal in association with the connecting information in the storage, and

in the relaying, the first relay apparatus establishes a connection with the target terminal on the basis of the terminal identification information associated with the connecting information and the port number of the target terminal in the storage.

4. The relay method according to claim 3 , wherein

in the acquiring, the relay system further acquires the port number of the target terminal from the client terminal, and

in the storing, the relay system further stores the acquired port number of the target terminal in association with the connecting information in the storage.

5. The relay method according to claim 1 , wherein

in the storing, the relay system stores the connecting information including the port number of the first relay apparatus in the storage,

in the notifying, the relay system notifies the client terminal about the connecting information including the address and the port number of the first relay apparatus, and

in the relaying, the first relay apparatus receives access based on the address and the port number of the first relay apparatus included in the connecting information from the client terminal.

6. The relay method according to claim 1 , wherein

in the storing, the relay system further stores the validity period information indicating a period in which the communication between the client terminal and the target terminal is available, in association with the connecting information in the storage, and

in the relaying, when the first relay apparatus receives the access based on the connecting information from the client terminal, the first relay apparatus relays the communication between the client terminal and the target terminal if the first relay apparatus determines that the communication is available on the basis of the validity period information associated with the connecting information in the storage, and stops relaying of the communication between the client terminal and the target terminal if the first relay apparatus determines that the communication is not available.

7. The relay method according to claim 6 , wherein

in the acquiring, the relay system further acquires the validity period information from the client terminal, and

in the storing, the relay system further stores the acquired validity period information in association with the specified connecting information in the storage.

8. The relay method according to claim 1 , wherein

in the acquiring, the relay system further acquires address information indicating an address of the client terminal when communicating with the target terminal from the client terminal,

in the storing, the relay system further stores the acquired address information in association with the specified connecting information in the storage, and

in the relaying, when the first relay apparatus corresponding to the connecting information receives access based on the connecting information from the client terminal, the first relay apparatus relays the communication between the client terminal and the target terminal if the relay apparatus determines that said address of the client terminal corresponds to the address information associated with the connecting information in the storage, and the first relay apparatus stops the relaying of the communication between the client terminal and the target terminal if the first relay apparatus determines that said address of the client terminal does not correspond to the address information.

9. The relay method according to claim 1 , wherein

in the relaying, the first relay apparatus further acquires client information indicating that the client terminal is eligible when the first relay apparatus receives the access based on the connecting information from the client terminal, relays the communication between the client terminal and the target terminal if the first relay apparatus determines that the client terminal is eligible on the basis of said client information, and stops the relaying of the communication between the client terminal and the target terminal if the first relay apparatus determines that the client terminal is not eligible.

10. The relay method according to claim 1 , wherein

in the relaying, the first relay apparatus relays the communication between the client terminal and the target terminal by communicating with the client terminal while encrypting data and communicating with the target terminal without encrypting data.

11. The relay method according to claim 1 , wherein

in the specifying the connecting information, the first relay apparatus is identified among a plurality of first relay apparatuses belonging to an area to which the client terminal belongs as the first relay apparatus that relays the communication between the client terminal and the target terminal.

12. The relay method according to claim 11 , wherein

in the specifying, the connecting information of the first relay apparatuses that belong to the area to which the client terminal that requested to connect to the target terminal belongs is specified by referring to address information by areas, in which a) the connecting information of the plurality of first relay apparatuses and b) areas where the first relay apparatuses are located are associated with each other.

13. The relay method according to claim 1 , wherein

in the relaying, the communication between the client terminal and the target terminal is relayed on a condition that the communication is within a communication validity period associated with the connecting information.

14. The relay method according to claim 1 , further comprising

notifying, relay information including a port number of the target terminal apparatus before the relaying, the relay information being notified by the connection management apparatus.

15. A relay system including

a first relay apparatus that is configured to relay a communication between (i) a target terminal which is provided in a closed network and assigned a private address and (ii) a client terminal which is not provided in the closed network;

a second relay apparatus that is configured to connect to the target terminal; and

a connection management apparatus that is configured to manage a connection at the time of relaying the communication between the client terminal and the target terminal, wherein

the connection management apparatus includes

an acquisition part configured to acquire a first connection request including terminal identification information for identifying the target terminal from the client terminal,

a specification part configured to specify, when the first connection request is acquired, connecting information for the client terminal to connect to the first relay apparatus, the connecting information indicating one port number selected from among a plurality of port numbers of the first relay apparatus that relays the communication between the client terminal and the target terminal,

a storage controller configured to store the connecting information in a storage in association with the terminal identification information, and

a notification part configured to notify the client terminal about the specified connecting information, wherein the first relay apparatus includes

a relay part configured to relay, responsive to a receipt by the first relay apparatus of a second connection request for communicating with the target terminal, addressed to the one port number indicated by the connecting information from the client terminal, the communication between the client terminal and the target terminal on the basis of the terminal identification information associated with the connecting information in the storage,

wherein the first relay apparatus is further configured to:

specify the second relay apparatus to which the target terminal is connected on the basis of the terminal identification information stored in the storage, and

relay communication between the client terminal and the target terminal via the specified second relay apparatus.