A relay server configured to serve as a second relay server connected to a second network, and communicate with a first relay server connected to a first network, the relay server comprising:
- a relay group information storage unit configured to store relay group information that indicates the first relay server, the second relay server, one or more client terminals connected to the first relay server via the first network, and one or more client terminals connected to the second relay server via the second network define a relay group;
- a relay server information storage unit configured to store relay server information including activation information of the first relay server, activation information of the second relay server, activation/registration information of the one or more client terminals connected to the first relay server, and activation/registration information of the one or more client terminals connected to the second relay server;
- an information sharing unit configured to allow the first relay server, the second relay server, the one or more client terminals connected to the first relay server, and one or more client terminals connected to the second relay server, to share the relay group information and the relay server information;
- a VLAN group information control unit programmed and configured to allow VLAN client terminals defining a VLAN group in the relay group to share VLAN group information, at least two of the one or more client terminals connected to the first relay server and the one or more client terminals connected to the second relay server being the VLAN client terminals, and the VLAN group information including hub information including identification information of the first relay server and identification information of the second relay server, to which the VLAN client terminal is connected, session information that indicates a connecting-side and a connected-side of a session established between the first relay server and the second relay server, and identification information that identifies the VLAN client terminals;
- an activation command control unit programmed and configured to transmit a response signal including address information of a VLAN device as an activatable VLAN client terminal in a case of receiving an activation instruction of the VLAN group;
- a VLAN session control unit programmed and configured to establish a hub session as a VLAN session between the first relay server and the second relay server based on the session information, and establish a device session as a VLAN session with the VLAN device connected to the second relay server;
- a relay server communication control unit programmed and configured to control communication between the VLAN devices, the communication being performed using virtual address information created for a VLAN device as an activatable VLAN client terminal among the VLAN client terminals defining the VLAN group based on the response signal, and the VLAN session;
- and
- a suspension processing unit programmed and configured to provide notification of suspension of the VLAN device;
- wherein
- if the suspension processing unit provides notification of suspension of the VLAN device, during a time when at least two VLAN devices are communicating with each other using the virtual address information and the VLAN session, the VLAN session control unit is programmed and configured to close the VLAN session related to the VLAN device about which suspension has been notified.