Discovery protocols are known as a technique for automatically acquiring service information of a network device connected on the same LAN. Discovery protocols are found in various forms. Examples of discovery protocols include UPnP (Universal Plug and Play), proposed by Microsoft, and Bonjour, proposed by Apple. There are various other ones, such as WS-Discovery and SLP (Service Location Protocol).
“Service information” refers to, for example, information (e.g., a service name) for identifying a service such as printing or file storing provided by a network device, and information required for connection, such as the network device name. A network device can easily implement connection with another network device by acquiring the service information of the other device.
In a discovery protocol, each device periodically broadcasts its service information over a network or inquires for the service information of a device at the other end, thereby managing a list of services on a LAN. In the case where an inquiry signal is sent to a device with service(s) that has once been found through a search and no response to the inquiry signal is detected, at the time of a service inquiry (search), it is determined that the device has left (disappeared from) the network and that provision of the service(s) in question by that device has stopped, and the connection with the service-providing-device at the other end is then disconnected.
Disconnecting a connection with a service-providing device is performed in a recognizable manner when the service-providing device has disappeared. The above-described service discovery is intended for a wired network. Accordingly, if there is no response to a service inquiry, it can be determined that the device at the other end has disappeared.
This causes a problem specific to wireless communication environments. Examples of such a problem include a temporary deterioration in radio wave conditions and various problems associated with movement of a device. If this kind of problem occurs, throughput decreases due to a temporary deterioration in radio wave condition at a wireless layer. However, connection with a device at the other end is still maintained, and a service-providing device is correctly performing processing.
In spite of this, if a service inquiry is sent, no response is obtained, at least temporarily, from the service-providing device. For this reason, a higher-level application which performs service discovery mistakenly determines that provision of a service has stopped and disconnects the lower-level (wireless layer) communication.