JP4174455B2 - Service use device - Google Patents

Description

The present invention relates to a service equipment which is connected to a network service providing equipment utilizes services provided.

  Currently, there are many digital devices having a digital interface. This type of digital device is connected via a digital interface to construct a network. However, conventionally, one network is constructed with one type of interface, and it has been difficult to construct different types of interfaces as one network.

  In order to solve this problem, UPnP (Universal Plug and Play) is currently proposed (see, for example, Non-Patent Document 1). UPnP can use IP (Internet Protocol) to communicate between different interfaces to build a single network.

FIG. 8 shows a configuration example of a UPnP network connected using a plurality of different interfaces. In FIG. 8 , a plurality of devices are connected using IEEE1394, Power Line, and Home PNA that are wired interfaces and 802.11b that is a wireless interface to form one UPnP network.

UPnP defines the functions of devices as services, and there are two devices on the UPnP network: “devices” that provide services and “control points” that control devices. For example, in FIG. 8 , PC1, PC2, NotePC and DTV can be used as control points to control the DVCR device. PC1 and PC2 are personal computers, NotePC is a notebook computer, DTV is a digital TV, and DVCR is a digital video camera.

  In UPnP, devices and control points use SSDP (Simple Service Discovery Protocol) to notify and detect services and the like. Notification of this service or the like is performed by transmitting a discovery message, and the discovery message is described using XML (Extensible Markup Language).

  When a device is connected to a UPnP network, it acquires an IP address from a DHCP server existing on the network, and multicasts the type of the device and the services that the device has as an ssdp: alive message. For example, when a device has a VTR function, the device describes information such as the type, recording format, and playback function of the corresponding recording medium in XML and transmits the information. Information such as supported recording media and recording formats are defined as state variables, and functions for performing device operations such as playback functions are defined as actions. When a device is disconnected from the UPnP network, it is recommended to send a multicast ssdp: bye-bye message notifying that the device is disconnected. The ssdp: alive message describes the period during which the device or service notified by this ssdp: alive message is valid. If the ssdp: bye-bye message is not sent, the control point has passed the valid period received. By doing so, the corresponding service is invalidated.

  When a control point is connected to the network, it obtains an IP address from a DHCP server on the network and waits for a service notification from a controllable device, or requests a search for the required service. Detect devices by multicasting over the network. Each device on the UPnP network receives this search request, and the device having the search target service transmits a response to the control point.

The control point that has acquired the necessary service in this way inquires the device about the state variable and requests the action. The inquiry or action request is transmitted from the control point to the device using an HTTP request, and the result is transmitted from the device to the control point using an HTTP response.
Universal Plug and Play Device Architecture, Version 1.0, 08 Jun2000

  However, in the above conventional example, a value during which the device or service notified by the ssdp: alive message is valid is specified to be greater than 1800 seconds (30 minutes). Therefore, if the device leaves the network without sending an ssdp: bye-bye message due to a sudden power failure, the worst case is that the removal is not recognized by the control point for 30 minutes. . In addition, when the control point displays a connection state such as an icon, the display lasts for 30 minutes in the worst case, and the current connection state cannot be properly displayed.

The present invention has been made to solve the above problems, the service providing apparatus connected to the network, if not send a message indicating the leaving from those the network, such as detached from the network even, and an object thereof is to provide a service using apparatus which can recognize promptly that the person the service providing apparatus is disconnected from said network.

Engaging Ru service using apparatus of the present invention, there is provided a service using apparatus service providing apparatus connected to the network to use the services provided, the first message a first time which indicates that the service is valid First determination means for determining whether or not the service has been received from the service providing apparatus before the elapse of time, and the first message from the service providing apparatus until the first time has elapsed. If it is not received, the transmission means for transmitting the second message for searching for the service providing apparatus, and the service providing apparatus until a second time elapses in response to the second message. And receiving a response from the service providing apparatus until the second time elapses. If no come, and judging with the service providing apparatus is disconnected from the network.

According to the present invention, the service providing apparatus connected to the network, even if not to send a message indicating the leaving from those the network as leaves from said network, quickly those said service providing apparatus There Ru can recognize that it has detached from the network.

Hereinafter, with reference to the accompanying drawings will be described implementation form of the present invention.

<First Embodiment>
A digital video camera as an example of a communication apparatus according to the first embodiment of the present invention will be described below with reference to FIG. The communication device according to the first embodiment of the present invention is not limited to a digital video camera, and may be a device such as a digital camera or an information terminal with a digital camera (including a mobile phone with a digital camera). 1, 701 is a microphone, 702 is an audio signal processing unit, 703 is a lens unit, 704 is an image sensor such as a CCD, 705 is a camera signal processing unit, 706 is a compression / expansion unit, 707 is a recording / playback processing unit, and 708 is a recording unit. A reproduction head, 709 is a recording medium such as a magnetic tape, 710 is a stream processing unit, 711 is a digital interface unit (hereinafter referred to as a DIF unit), 712 is a central processing unit (hereinafter referred to as a CPU), and 713 is a wireless circuit. 714 is an antenna (hereinafter referred to as an RF circuit).

  The operation of the digital video camera having the above configuration will be described. The audio signal input to the audio signal processing unit 702 through the microphone 701 is input to the compression / decompression processing unit 706. An image signal formed by the lens unit 703 and output from the CCD 704 is input to the compression / expansion processing unit 706 in the same manner. During the photographing operation, the compression / decompression processing unit 706 performs a compression operation on the input image signal and audio signal. For example, the compression / decompression processing unit 706 performs DV compression processing for recording on a recording medium and MPEG-4 compression processing for DIF output. The compressed image signal and audio signal are subjected to recording processing in a recording / playback processing unit 707 and then recorded on a recording medium 709 via a head 708. When the compressed image signal and audio signal are wirelessly output to the outside, the compressed image signal and audio signal are input to the stream processing unit 710 to be packetized, and after being packetized, DIF The signal is output to the outside via the unit 711, the RF circuit 713, and the antenna 714.

  Further, during the reproduction operation, the compression / decompression processing unit 706 performs an expansion operation. For example, assuming that data subjected to DV compression processing is recorded on the recording medium 709, the DV signal reproduced by the head 708 is reproduced by the recording / reproduction processing unit 707, and the compression / decompression processing unit 706 is obtained. DV decompression processing is performed at. The image signal after the DV expansion processing is sent to a display device (not shown) (for example, a display panel included in the video camera) and displayed. In addition, when the playback image is transmitted to the outside, the compression / decompression processing unit 706 performs, for example, MPEG-4 compression processing for DIF output. The MPEG-4 compressed image signal is input to the stream processing unit 710 to be packetized, and after being packetized, is output to the outside via the DIF unit 711, the RF circuit 713, and the antenna 714, respectively. . In the digital video camera of this embodiment, the DIF unit 710 and the RF circuit 713 are digital interfaces (DIF) using a known wireless LAN technology according to the IEEE802.11a standard, for example. It goes without saying that other standards such as IEEE802.11b and IEEE802.11g may be used for this wireless LAN technology.

  Next, a digital television device (hereinafter referred to as a digital television) according to the present embodiment will be described with reference to FIG. In FIG. 2, a radio frequency (RF) signal is supplied to the RF input terminal 400 of the tuner 402. The tuner 402 selects individual signals under the control of the tuner control unit 404. The control unit 404 supplies a tuning control signal to the tuner 402 via the signal line 403, and supplies a band switching signal via the control bus 403 ′. The tuner control unit 404 is controlled by the microprocessor 410. The microprocessor 410 is a controller or microcomputer, and includes a central processing unit (CPU) 412, a read only memory (ROM) 414 and a random access memory (RAM) 416. The microprocessor 410 receives a control signal input by a user from an input switch (SW) 420 and an infrared (IR) receiver 422. The IR receiver 422 receives and decodes the remote control signal transmitted from the remote control transmitter 425.

  The tuner 402 generates an intermediate frequency (IF) signal and supplies it to the processing unit 430. The processing unit 430 comprises a video IF (VIF) amplification stage, an AFT circuit, a video detector and an audio IF (SIF) amplification stage. The processing unit 430 generates a baseband video signal (TV) and an audio carrier signal. The audio carrier signal is supplied to an audio signal processing circuit 435 including an audio detector and a stereo decoder. The audio signal processing circuit 435 generates left and right baseband audio signals and supplies them to a pair of speakers 438 to reproduce the audio.

  The baseband video signal (TV) output from the processing unit 430 is input to the switching unit 453. A video input terminal 442 (AUX input) is provided for receiving a baseband video signal from an external signal source. The input signal from the AUX input terminal 442 is supplied to the switching unit 453 similarly to the TV signal described above, and the output to the video signal processing circuit 455 is selected by the switching signal from the microprocessor 410. The video signal processing circuit 455 processes the input signal and finally displays it on the screen of a display device (not shown). The video signal is also supplied to the sync separation circuit 460. The sync separation circuit 460 extracts a vertical sync signal and a horizontal sync signal from the video signal. The extracted vertical and horizontal synchronization signals are supplied to the microprocessor 410 and the deflection unit 470, and a deflection signal is generated and supplied to a yoke structure (not shown).

  Microprocessor 410 is coupled to a digital interface (DIF) unit 495. The DIF unit 495 is connected to the outside via an interface port (not shown). The DIF unit 495 is, for example, a digital interface using IEEE1394. An external command can be input using an IEEE1394 asynchronous communication method, and a video signal is input using an IEEE1394 isochronous communication method. The input video signal is appropriately processed by the DIF unit 495 and input to one terminal of the switching unit 453. As described above, the switching unit 453 can select and display one of the tuner input, the AUX input, and the DIF unit input. A signal from the tuner 402 is also input to the DIF unit 495. When the DIF unit 495 is controlled to be an external output, a signal from the tuner is output to the outside as an isochronous signal. A command using the above-described Asynchronous communication method is input to the microprocessor 410, and a control operation corresponding to the command is performed.

  Next, an example of a network connection mode according to the present embodiment will be described with reference to FIG. Reference numeral 300 denotes a digital video camera (video camera) according to the present embodiment, 302 denotes a digital television, and 304 denotes a wireless LAN access point (hereinafter referred to as an access point). As described above, in the video camera 300 according to the present embodiment, for example, a well-known wireless LAN technology is used according to the IEEE802.11a standard. Therefore, there is a physical connection between the video camera 300 and the access point 304 by wiring or the like. No connection has been made. However, the video camera 300 and the access point 304 can communicate with each other via a wireless LAN. On the other hand, the digital television 302 and the access point 304 are connected by IEEE1394, and communicate with each other using, for example, RFC2734 “IPv4 over IEEE 1394” standard. Of course, it goes without saying that the digital television and the access point of this embodiment may be connected using other communication methods such as Ethernet (registered trademark).

  In the present embodiment, the video camera 300 and the digital television 302 communicate with each other using, for example, a known TCP / IP protocol. At this time, the access point 304 controls the route of the TCP / IP packet as a router. In association with UPnP, the digital television 302 of this embodiment functions as a control point (CP), the video camera 300 functions as an Audio / Video (AV) device, and the access point 304 functions as an Internet Gateway device (IGD). In UPnP, “device” provides various services to “control point” on the network, and “control point” uses various services by performing various controls using “device” service. The function can be realized.

  When connection to the network is established by turning on the power or establishing a physical connection, the video camera 300, the digital television 302, and the access point 304 try to acquire an IP address. These devices first try to obtain an IP address from a DHCP server, for example according to the RFC 2131 “Dynamic Host Configuration Protocol” standard, so-called DHCP. If an IP address cannot be obtained by DHCP because there is no DHCP server on the network, the above device will send an Internet address "http://www.upnp.org/download/draft-ietf-zeroconf -IPv4-linklocal-01-Apr.txt "publicly known," Dynamic Configuration of IPv4 link-local addresses "standard for determining IP addresses Determines the IP address of the device using the so-called AutoIP standard .

  Next, a data exchange procedure according to this embodiment will be described with reference to FIG. FIG. 4 is a sequence chart showing the data exchange operation according to this embodiment using the ITU-T Recommendation Z.120, Message Sequence Chart standard. When the IP address is determined, the video camera 300 transmits an Advertise message to all devices on the network by so-called broadcast. This Advertise message uses a message of the ssdp: alive format, and the above transmission form is called “Advertisement”. By this advertisement, the control point on the network can acquire information that the device or the service that the device has becomes effective, and information such as what service or device exists on the network. In the present embodiment, the digital television 302 serving as a control point acquires, for example, function information and control information possessed by the video camera 300 and the access point 304, or attribute information of the device.

  Next, the digital television 302 performs a display for identifying and selecting the video camera 300 such as an icon on the display surface of the digital television based on the information acquired by the above-described advertisement. The video camera 300 according to the present embodiment notifies, for example, that the service valid period is 1800 seconds (30 minutes) by using the ssdp: alive message. That is, in the digital television 302 as a control point, the service valid period of the video camera 300 is set to 1800 seconds (30 minutes). The video camera 300 periodically transmits an ssdp: alive message to the digital television 302 at an interval shorter than the effective period of 1800 seconds (30 minutes). Each time the digital television 302 receives the ssdp: alive message, the digital television 302 measures the time interval at which the ssdp: alive message arrives and starts the first timer. The first timer is reset every time an ssdp: alive message arrives.

  Here, a default value is set as an initial value for the timeout value of the first timer, but thereafter, the timeout value is set based on a representative value obtained by performing statistical processing of a time interval at which the ssdp: alive message arrives. . For example, the arithmetic average of the time interval at which the ssdp: alive message arrives is calculated, and the timeout value of the first timer is set based on the calculated value. This value is not limited to the arithmetic mean, and other representative values such as a statistical median (median) or mode (mode) may be used. When the median value or the mode value is used, there is an effect that the operation can be made more robust against an outlier value caused by a measurement error or the like than the average value. In addition, since the control point can dynamically set the timeout time of the ssdp: alive message by the above operation, the time interval at which the ssdp: alive message sent from the device arrives at the control point differs depending on the device. Even if it is, there is an effect that can be easily handled.

  Normally, the ssdp: alive message is received from the video camera 300 within the set time interval, that is, without the first timer being timed out. However, if communication between the video camera 300 and the digital television 302 becomes impossible due to the video camera 300 going out of the wireless LAN reachable range, the ssdp: alive message does not reach the digital television 302. The first timer times out.

  When the first timer times out, the digital television 302 performs a search operation for transmitting a search message to the video camera 300 based on the timeout information and starts the second timer. Normally, the video camera 300 is configured to respond to the search operation within a predetermined time. As described above, when the video camera 300 is out of the wireless LAN reachable range, the second timer times out. Will be generated. Based on the time-out information, the digital television 302 determines that the video camera 300 is disconnected, and erases the display of the icon indicating the video camera 300 and the like. With the above operation, even when the device is unexpectedly disconnected from the network or suddenly shuts down, the control point can quickly detect the state and reflect it on the display. The search operation is performed by, for example, a ssdp: discover message using a known HTTP M-SEARCH method.

  Next, an operation when the communication state is restored due to the reason that the first timer times out and returns to the wireless reachable range will be described. FIG. 5 is a sequence chart showing the operation of this embodiment using the ITU-T Recommendation Z.120, Message Sequence Chart standard as in FIG. As in FIG. 4, when the IP address is determined, information acquisition and icon display are performed by the Advertise message, and reception of the ssdp: alive message is started. That is, every time an ssdp: alive message is received, the time interval at which the ssdp: alive message arrives is measured and the first timer is started.

  As described above, when communication between the video camera 300 and the digital TV 302 becomes impossible due to the video camera 300 going out of the wireless LAN reachable range, the ssdp: alive message does not reach the digital TV 302. The first timer times out. When the first timer times out, the digital television 302 performs a search operation for transmitting a search message to the video camera 300 based on the timeout information, and starts the second timer. Here, when the video camera 300 returns to the wireless LAN wireless area, a response to the search request is received before the second timer times out, and the second timer does not time out. For this reason, the digital television 302 recognizes that the above-described video camera 300 is still connected, and maintains the display of an icon or the like indicating the video camera 300.

  With the above operation, there is an effect that the display of the controller can be made robust even when the device frequently moves between the wireless reachable range and the impossible range around the wireless LAN reachable range. The search operation is performed by, for example, a ssdp: discover message using a known HTTP M-SEARCH method.

Next, the operation of the control point according to the present embodiment will be described with reference to FIG. Figure 6 is a flowchart showing the operation of the control points of the present embodiment.

  The operation is started in step S1, and initial setting is performed in the next step S2. In step S3, the reception of the above-described Advertise message is waited. When the Advertise message is received, device data is analyzed based on the information of the Advertise message received in step S4. In the next step S5, the icon of the device that has been advertised is displayed. As described above, the device according to the present embodiment periodically transmits the ssdp: alive message to the controller at intervals shorter than 1800 seconds (30 minutes), for example. In the next step S6, it waits for the ssdp: alive signal transmitted from the device.

  When receiving the ssdp: alive signal, the control point sets a predetermined value (default value) as a Timeout value in step S7 and starts the first timer. In the next step S8, a timeout is determined for the first timer. If the first timer has not expired in step S8, the process proceeds to the next step S9. In step S9, the ssdp: alive signal transmitted from the device is again waited. When the control point receives ssdp: alive in step S9, in next step S10, an average arrival time which is an average reception interval of the ssdp: alive signal is calculated, and a Timeout value is calculated based on the average arrival time. Set to the first timer. Then, the first timer is restarted, and the process returns to step S8. In step S10, the average value of arrival times of the ssdp: alive signal is calculated and set as the Timeout value. As described above, this value is a median value, a mode value (mode), or the like. Other representative values may be used.

  On the other hand, if ssdp: alive has not been received in step S9, a timeout determination is made for the first timer in step S8. If the first timer expires in step S8 and a timeout has occurred, search: request is transmitted to the device in the next step S11 to start the device search operation. The search: request signal is, for example, an ssdp: discover message using a known HTTP M-SEARCH method. Thereafter, in step S12, a predetermined value (default value) predetermined for the Timeout value is set in the second timer, and the second timer is started.

  In the next step S13, a timeout is determined for the second timer. If the time-out has not occurred in step S13, a search: response signal is waited for in step S14. The search: response signal is a device response signal to the search: request signal, and is a response to the search operation. If the search: response signal has not been received in step S14, the process returns to step S13, and a timeout is determined for the second timer. When the search: response signal is received in step S14, the process returns to step S7 described above, and the ssdp: alive signal reception process is resumed. In the present embodiment, the operation of steps S7 to S14 has an effect that communication can be easily restarted even when communication between the device and the controller is disabled for a short period of time. On the other hand, if the second timer has timed out in step S13, the display of icons and the like is deleted in the next step S15, and the connection state registration is also released. In step S16, the operation of the present embodiment ends.

  The above process is performed for each device whose connection is registered in the network.

[Description of ssdp: alive]
As described above, ssdp: alive is a message signal transmitted from a device that has joined the network and indicating that the device is valid or that one of the services of the device is valid. When a device joins the network, the device uses ssdp: alive to make all devices on the network aware of the services it provides. The ssdp: alive message is transmitted using, for example, the NOTIFY method of GENA (General Event Notification Architecture) on the SSDP multicast channel. GENA is a known protocol by the document “GeneralEventNotification Architecture Base: Client to Arbiter” published at the Internet address “http://www.upnp.org/download/draft-cohen-gena-client-01.txt”. It is a protocol for sending and receiving event messages. In GENA, devices or devices that transmit and receive messages are called publishers and subscribers. The subscriber requests, updates, and cancels the event issuance reservation. The publisher also issues events. Thus, in GENA, an event is transmitted from a publisher to a subscriber. The SSDP is a protocol for discovering resources based on HTTP on a local area network (LAN). SSDP is a well-known protocol according to the document “SimpleServiceDiscovery Protocol / 1.0” published on the Internet address “http://www.upnp.org/download/draft_cai_ssdp_v1_03.txt”.

As described above, when a device joins the network, the device announces that the SSDP service exists by sending a message using the NOTIFY method on the SSDP multicast channel. The message includes data on the request line of the message indicating that the message is a GENA message. The request line is, for example,
NOTIFY * HTTP / 1.1
It is like this.

  The ssdp: alive message includes a header as additional information. Table 1 shows the contents of the header of the ssdp: alive message.

  The expiration information provided by the Cache-control header in Table 1 informs the control point how long information about the service must be retained in the cache memory of the control point. . When this period expires, the control point must discard the information from the control point cache. The ssdp: alive message described above is also used for the purpose of indicating to the control point that the service of the device can be continuously used before the cache memory entry is deleted due to expiration of the expiration date.

[Description of ssdp: discover]
As described above, the ssdp: discover request uses the well-known HTTP method M-SEARCH and includes the search target ST in the header of the ssdp: discover message. The client sets the type of service that the client wants in the ST. It is not allowed to include multiple ST headers in one ssdp: discover message. Also, complex searches such as logical operations and name / value pairs are not supported as well. The request line of the ssdp: discover message is, for example, an M-SEARCH request line with “*” indicating that a search is performed for all listed devices in the Request-URI. For example,
M-SEARCH * HTTP / 1.1
become that way.

  UPnP control points and devices use the SSDP URI search capability, but also use special conventions for the ST header in the ssdp: discover message. By setting different values in the ST header in the ssdp: discover message, the UPnP control point can search for all devices, root devices, specified device types, specified service types, and the like. Table 2 shows the headers used for SSDP requests.

  Once the searched device or service is detected, a response message to the ssdp: discover message is directly transmitted as a unicast message to the transmission device of the ssdp: discover message. At this time, the ssdp: discover message includes period information and location information in addition to the service type and the unique service name of the service to be searched. Table 3 shows headers used in response to the ssdp: discover message.

  For UPnP devices, the USN field takes a number of different formats depending on the type of request contained in the ST header in the initially transmitted ssdp: discover message. The format of the ST header is shown in Table 4 below.

  As described above, in the present embodiment, even when a device connected to a network cannot send a message indicating the departure from the network and leaves the network, the controller promptly There is an effect that it can be recognized that the device is detached. In addition, when the connection between devices connected to the network is disconnected for some reason, it is possible to provide a device that can promptly reflect the disconnected state on the display. Furthermore, since the timeout value of the first timer is set based on the time measurement result of the ssdp: alive reception interval from the device (access point), the determination as to whether the device has left the network is accurate and robust. can do.

Second Embodiment
In the first embodiment, a case has been described in which an access point is newly added to a place where the control point is already connected to the network. Therefore, it was possible to recognize the connection of the access point by receiving the advertisement from the access point. However, if the control point is connected to a network to which the access point has already been connected, the access point itself has already joined the network, so the advertise message until just before the service expires. Will not be issued. Therefore, a time difference that cannot be ignored occurs until the control point recognizes the connection of the access point. In the second embodiment, even in such a case, it is possible to quickly recognize the connection of the access point.

  FIG. 7 is a flowchart showing the operation at the control point according to the second embodiment. In FIG. 7, the same reference numerals as those in FIG. 6 indicate the same processes. FIG. 7 differs from the flowchart of FIG. 6 in that access point subscription recognition is performed using the ssdp: alive message. That is, when the operation is started in step S1, initialization is performed in step S2. In step S6, it waits for the ssdp: alive signal transmitted from the device. As described above, the device according to the present embodiment periodically transmits the ssdp: alive message to the controller at intervals shorter than 1800 seconds (30 minutes), for example. In step S4, device data is analyzed based on the received ssdp: alive signal, the connection of the device to the network is registered, and a device icon is displayed in step S5. Thereafter, the operations described in the first embodiment are executed in steps S7 to S15.

  As described above, according to the second embodiment, since the connection to the network is recognized using the ssdp: alive message periodically issued from the access point, the device can be recognized according to the actual connection state. It becomes possible.

  Note that the processing described with reference to FIG. 7 can also be applied to the case where the second timer has timed out in step S13 of the first embodiment or the second embodiment and the device determined to be in the disconnected state returns to the network again. In other words, even if the control point is recognized as disconnected, the device itself may still recognize that it is connected to the network, and in such cases, issuing an advertisement from the device is valid. Not done until the expiration of the period. However, according to the series of processes in steps S2, S6, and S4 of FIG. 7, the device can be quickly re-registered.

<Third Embodiment>
Next, a third embodiment will be described. In the third embodiment, a modification of the timeout value setting process of the first timer is shown.

  In the first and second embodiments, the Timeout value is set based on the average value of the arrival times of ssdp: alive in the Timeout value setting process in Step S10. Further, it has been described that, in addition to using the average value, other representative values such as a median value (median) and a mode value (mode) may be used. In the third embodiment, the Timeout value is determined in consideration of the value calculated from the variance of the arrival time of ssdp: alive, the standard deviation, and the range.

In step S10 of FIG. 6 or FIG. 7, the average arrival time t ₁ that is the average reception interval of the ssdp: alive signal and the standard deviation σ of the arrival interval are calculated, and the measured current arrival interval t is measured so far. From the maximum value t _max and the minimum value t _{min of} the arrival intervals, for example, the timeout value t _out is calculated according to the following equation.

In step S10, this _timeout is set in the Timeout value of the first timer to restart the first timer, and the process returns to step S8.

In the above description, the average value of the arrival times of the ssdp: alive signal is t ₁ , but other representative values such as a statistical median (median) or mode (mode) may be used as t ₁ . Further, instead of the standard deviation σ, it may be calculated using a scale such as variance and range (difference between the maximum value tmax and the minimum value tmin).

  As described above, according to the third embodiment, the controller can dynamically set the timeout time of the ssdp: alive message, and statistically process the arrival time interval of the ssdp: alive message in the setting. Thus, a more appropriate timeout time can be set, and the detection of device detachment can be performed more quickly and accurately.

<Other embodiments>
Another object of the present invention is to supply a storage medium storing software program codes for implementing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

1 is a block diagram illustrating a digital video camera according to a first embodiment. It is a block diagram which shows the digital television by 1st Embodiment. It is a figure which shows the example of a connection by 1st Embodiment. It is a sequence diagram which shows the data transfer procedure of 1st Embodiment. It is a sequence diagram which shows the data transfer procedure of 1st Embodiment. It is a flowchart which shows operation | movement of the control point of 1st Embodiment. It is a flowchart which shows operation | movement of the control point of 2nd Embodiment. It is a figure which shows a prior art example.

Claims (6)

A service using device that uses a service provided by a service providing device connected to a network,
First determination means for determining whether or not a first message indicating that the service is valid has been received from the service providing apparatus until a first time has elapsed;
A transmitting means for transmitting a second message for searching for the service providing apparatus when the first message cannot be received from the service providing apparatus until the first time elapses;
Second determination means for determining whether or not a response to the second message has been received from the service providing apparatus until a second time elapses;
Have
The service using apparatus, wherein if the response cannot be received from the service providing apparatus before the second time elapses, it is determined that the service providing apparatus has left the network. When the first message can be received from the service providing apparatus before the first time elapses, the first determination unit again transmits the first message to the first time. The service use apparatus according to claim 1, wherein it is determined whether or not the service has been received from the service providing apparatus until the time has elapsed. When the response can be received from the service providing apparatus before the second time elapses, the first determination unit again receives the first message until the first time elapses. The service use apparatus according to claim 1, wherein a determination is made as to whether or not the service has been received from the service providing apparatus. A display unit for displaying an icon corresponding to the service providing apparatus;
The display of the icon is erased when the response cannot be received from the service providing apparatus before the second time elapses. The service utilization apparatus as described. The first message is an ssdp: alive message;
The service use apparatus according to claim 1, wherein the second message is an ssdp: discover message. The service providing apparatus is a device in UPnP,
6. The service utilization apparatus according to claim 1, wherein the service utilization apparatus is a control point in UPnP.

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