JP5982436B2 - Screen transfer server device and screen transfer method - Google Patents

Description

  Embodiments described herein relate generally to a screen transfer server and a screen transfer method for transferring screen data based on a user operation.

With the spread of cloud applications, an application for transferring screen data from a server to a client (terminal device on the user side) is increasing based on user operations.
As this application, for example, a thin client, application virtualization, and an edge server that takes over terminal processing in an edge computing platform as disclosed in Non-Patent Document 1, for example (hereinafter referred to as an output function division server) And so on).

  In these technologies, since the server continuously transmits screen data to the client, the consumption of the network bandwidth is a problem. Therefore, when screen data is sent from the server to the client, not all screen data is sent at once, but only the minimum data required for screen display is sent, thereby reducing network bandwidth consumption. There is a need to reduce. On the other hand, when screen data update or display area update occurs, the updated screen data must be promptly transmitted to the client and provided to the user.

  As a bandwidth reduction technique related to screen data transfer, for example, as shown in Non-Patent Document 2, a method of adjusting a transmission interval according to a delay amount in a display driver, or as shown in Non-Patent Document 3, for example, There is a method of switching the transmission method to a moving image or a still image according to the update amount for each screen area.

“Developing an“ edge computing concept ”to promote the development of new applications that require high response and big data processing”, [online], NTT Holding Company news release, January 23, 2014, [2014 Search on July 23rd], Internet <URL: http://www.ntt.co.jp/news2014/1401/140123a.html> Shinya Murai, Hiroshi Kawazoe, “PC Screen Transfer Technology for Application Sharing”, [online], Toshiba Review 2006 VOL.61 NO.4, [Search July 23, 2014], Internet <URL: https: / /www.toshiba.co.jp/tech/review/2006/04/61_04pdf/a06.pdf> Kazuki Matsui and three others, “High-speed display technology in virtual desktop environment: RVEC”, [online], FUJITSU 2012-January issue (Vol.63, No.1), [July 2014 Search on the 23rd], Internet <URL: http://img.jp.fujitsu.com/downloads/jp/jmag/vol63-1/paper12.pdf>

  However, the method disclosed in Non-Patent Document 2 is a method of detecting data congestion and reducing the data transmission rate. In this method, the minimum necessary screen data cannot be sent to the client in consideration of the fact that the display area has been updated as the user operates the client.

  Further, the method disclosed in Non-Patent Document 3 is a method of switching the transmission method to either a moving image or a still image, and cannot reduce the bandwidth of image transfer.

  Further, any of the above methods is not a screen transfer method considering partial update of the display screen by a user operation, but a method of transferring the entire screen data.

  An object of the present invention is to provide a screen transfer server device and a screen transfer method that can reduce the bandwidth associated with the transfer of screen data while maintaining response performance to screen updates.

In order to achieve the above object, a first aspect of the screen transfer server device according to the embodiment of the present invention includes a screen data creation unit that creates the latest screen data for each predetermined period, and the created latest screen. An acquisition unit that acquires data, a holding unit that holds screen data acquired last time by the acquisition unit, and a difference between the acquired latest screen data and the held screen data acquired last time is transmitted to the client device. A transmission control unit, and when the screen data read request is generated in the client device, the screen data generation unit extends a screen data generation cycle until a predetermined time elapses after receiving the request. A screen transfer server device is provided.
In order to achieve the above object, a second aspect of the screen transfer server device according to the embodiment of the present invention includes a screen data creation unit that creates the latest screen data for each predetermined period, and the created latest screen. An acquisition unit that acquires data, a holding unit that holds screen data acquired last time by the acquisition unit, and a difference between the acquired latest screen data and the held screen data acquired last time is transmitted to the client device. A transmission control unit, and the transmission control unit, when scrolling on the screen on the client device, the actual scrolling amount after the operation for scrolling on the screen on the client device is made The screen data corresponding to the difference is scrolled by the operation in consideration of the time difference until it reaches the client device. Provided is a screen transfer server device that transmits screen data corresponding to a difference between a screen before scrolling and a screen after scrolling to the client device based on a scroll amount that is increased by a predetermined expected scroll amount. To do .

According to a third aspect of the screen transfer server device configured as described above, in the first or second aspect, the difference is the acquired latest screen data and the held previous time in a rectangular area defined on the screen. This is screen data corresponding to the difference from the acquired screen data.

According to a fourth aspect of the screen transfer server device configured as described above, in the first or second aspect, the difference is the acquired latest screen data and the retained previous acquired screen in bit units on the screen. This is screen data corresponding to the difference from the data.
According to a fifth aspect of the screen transfer server device configured as described above, in the first aspect, the transmission control unit is obtained from information acquired from the client device when the screen on the client device is scrolled. Based on the scroll amount, screen data corresponding to the difference between the screen before scrolling and the screen after scrolling is transmitted to the client device.

A first aspect of a screen transfer method according to an embodiment of the present invention is a method applied to a screen transfer server device, wherein the screen transfer server device creates the latest screen data every predetermined cycle, and The latest screen data created is acquired, the screen data acquired last time is retained, the difference between the acquired latest screen data and the retained screen data is transmitted to the client device, and the screen is displayed on the client device. When a data read request is generated, the screen data creation cycle is extended until a predetermined time elapses after the request is received .
A second aspect of the screen transfer method according to the embodiment of the present invention is a method applied to a screen transfer server device, wherein the screen transfer server device creates the latest screen data every predetermined cycle, and The latest screen data created is acquired, the screen data acquired last time is retained, the difference between the acquired latest screen data and the retained screen data is transmitted to the client device, and the client device When the screen is scrolled, the actual scrolling amount is taken into account the time difference from when the operation for scrolling the screen on the client device is performed until the screen data corresponding to the difference reaches the client device. , Based on the scroll amount increased by a predetermined scroll amount expected to be scrolled by the operation, Transmitting the screen data corresponding to the difference between the screen after crawling previous screen and scroll to the client device.

  According to the present invention, it is possible to reduce the bandwidth associated with the transfer of screen data while maintaining response performance to screen update.

The figure which shows an example of the procedure of the screen transfer by the screen transfer system in embodiment of this invention. The figure which shows an example of the difference of the screen by the screen transfer system in embodiment of this invention. The figure which shows an example of the form of the scroll of the screen by the screen transfer system in embodiment of this invention. The figure which shows an example of the procedure of the screen transfer accompanying the scroll operation of the screen by the screen transfer system in embodiment of this invention. The figure which shows an example of the form of the extension of the drawing process space | interval of screen data by the screen transfer system in embodiment of this invention. The figure which shows the 1st example of a function structure of the screen transfer system in embodiment of this invention. The figure which shows the 2nd example of a function structure of the screen transfer system in embodiment of this invention. The figure which shows the 3rd example of a function structure of the screen transfer system in embodiment of this invention.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an example of a screen transfer procedure by the screen transfer system according to the embodiment of the present invention.
The screen transfer system according to the present embodiment includes a client 10 used by a user and a server 20 that performs screen transfer (hereinafter referred to as server 20).
In this system, when there is a change in the screen area of the screen data transmitted from the server 20 to the client 10, the screen data transmitted to the client 10 is updated.

  The server 20 includes a screen data transmission control unit 21 and a screen data creation unit 22. The screen data transmission control unit 21 transmits screen data to the client 10. The screen data creation unit 22 creates screen data for the client 10.

The server 20 incorporates a drawing timer, and interrupts the screen data transmission control unit 21 by operating the drawing timer at regular intervals.
The screen data transmission control unit 21 detects an interruption by the drawing timer and transmits a screen data acquisition request to the screen data creation unit 22.
In response to the screen data acquisition request, the screen data creation unit 22 creates the latest screen data and transmits it to the screen data transmission control unit 21.

The screen data previously transmitted from the screen data creation unit 22 to the screen data transmission control unit 21, that is, the screen data created once before the latest screen data is held in the storage device in the server 20.
The screen data transmission control unit 21 sends the latest screen data acquired from the screen data creation unit 22 and the screen data held in the storage device as described above, that is, from the screen data creation unit 22 to the screen data transmission control unit 21 last time. Compare the transmitted screen data and check the difference between both screen data.

  When there is a difference between the two screen data, the screen data transmission control unit 21 transmits a request message indicating the difference screen data to the client 10. The screen data held in the storage device as described above is updated to the latest screen data created by the screen data creation unit 22 as described above. The updated screen data is used as the screen data transmitted last time from the screen data creation unit 22 to the screen data transmission control unit 21 in the comparison of differences after the next time.

When the client 10 receives the difference screen data from the server 20, the client 10 updates the display screen based on the difference screen data and sends a response message indicating that the difference screen data has been received to the screen data transmission control unit of the server 20. To 21. When the difference screen data is transmitted using a reliable protocol (for example, TCP), the response message may be omitted.
The difference check may be performed on a rectangular area defined in advance on the screen data, or may be performed on a bit unit on the screen data.

Next, the operation when scrolling the screen will be described. When the user performs a scroll operation on the screen of the client 10, the client 10 measures the scroll amount.
If the display device of the client 10 is a touch panel, the scroll amount is calculated as the amount of screen movement with respect to the elapsed time from the event occurrence time, based on the event occurrence position and speed on the screen. If the input device of the client 10 is a remote controller, the scroll amount is calculated based on the scroll amount assigned to one button operation of the remote controller.

The client 10 transmits information indicating the calculated scroll amount to the server 20. The latest scroll position information is held in a storage device in the server 20. The server 20 updates the scroll amount information by overwriting the scroll amount information from the client 10 on the scroll position information held in the storage device in the own device. Based on the latest screen data held in the storage device and the updated scroll amount, the screen data transmission control unit 21 calculates the difference screen data corresponding to the updated scroll amount, that is, the screen before scrolling and the screen after scrolling. A difference from the screen is calculated, and a request message indicating the difference screen data is transmitted to the client 10. Thereby, a difference can be obtained without comparing the screen data as described above.
Alternatively, the client 10 can store the latest scroll position in the storage device, calculate the coordinates of the screen data that needs to be updated based on the occurrence position and speed of the event, and transmit the calculated data to the server 20. . Alternatively, the client 10 measures the event occurrence position and speed, and transmits the information to the server 20, so that the server 20 can calculate the amount of screen movement with respect to the elapsed time from the event occurrence time.

FIG. 3 is a diagram showing an example of a screen scroll mode by the screen transfer system according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a screen transfer procedure associated with a screen scroll operation by the screen transfer system according to the embodiment of the present invention.
FIG. 3 shows an image when the scroll direction is downward. The scroll detection direction in this embodiment can be applied to any scroll direction, up, down, left, and right, but can also be applied to only some scroll directions.

  In the transmission of the difference information, since there is a time difference from when the user performs a scroll operation on the client 10 until the screen information actually reaches the client 10 from the server 20, the operation feeling for the user is unnatural. There is a case.

  In order to eliminate this unnatural feeling of operation, the screen data transmission control unit 21 adds a predetermined value corresponding to the scroll amount expected to be scrolled by the user later to the scroll amount transmitted from the client 10. A so-called prefetching process is performed in which a difference screen corresponding to the scroll amount is created and a request message indicating the difference screen data is transmitted to the client 10. This pre-reading process can also be applied to any scroll direction, up, down, left, and right. In this prefetching process, a scroll amount obtained by adding a predetermined value to the scroll amount measured by the client 10 by the client 10 can be transmitted to the server 20.

Next, a sequence for reducing the network bandwidth by changing the operation interval (drawing processing interval) of the drawing timer according to the screen reading state will be described.
FIG. 5 is a diagram showing an example of a form of extending the screen data drawing processing interval by the screen transfer system according to the embodiment of the present invention.

Specifically, the server 20 includes a scheduler for managing the screen data drawing (creation) processing interval by the screen data creation unit 22.
In accordance with the screen data read request from the user, the client 10 transmits a screen data read request to the server 20.
Thereby, the screen data creation unit 22 of the server 20 creates screen data based on the drawing start instruction from the scheduler 23. Immediately after the screen data creation unit 22 starts drawing the screen data, the screen page drawing update frequency is low. For this reason, the drawing processing interval is extended to t2 longer than the normal interval t1 for a fixed time after the screen data reading unit 22 receives the screen data reading request. The scheduler 23 performs a thinning process on the drawing start instruction interval to the screen data creation unit 22. This reduces the frequency of screen transfer updates.
When the predetermined time has elapsed, the drawing processing interval in the screen data creation unit 22 is returned to t1 which is a normal drawing processing interval.

Hereinafter, various embodiments of the screen transfer system will be described.
(First embodiment)
FIG. 6 is a diagram illustrating a first example of a functional configuration of the screen transfer system according to the embodiment of the present invention.
The system shown in FIG. 6 is applied to, for example, an online game or an electronic book system.

  In the system shown in FIG. 6, the client 10 uses a service provided by the server 20 for providing a screen transfer service. The server 20 includes a screen data transmission control unit 21, a screen data creation unit 22, a scheduler 23, a screen data holding unit 24, and a storage device 25.

  The client 10 transmits a content acquisition request to the server 20 via the network (NW) 30. The content acquisition request includes the server and information (for example, URI) that can specify the content.

After acquiring the screen data acquisition request, the screen data creation unit 22 creates the latest screen data (content) by interruption by the drawing timer, and transmits the screen data to the screen data transmission control unit 21.
The screen data previously transmitted from the screen data creation unit 22 is held in the storage device 25 in the server 20 by the screen data holding unit 24 in the server 20. The screen data transmission control unit 21 includes the latest screen data transmitted from the screen data creation unit 22 and the screen data held in the storage device 25 as described above, that is, from the screen data creation unit 22 to the screen data transmission control unit 21. Compare the previous screen data sent to and check the difference between the screen data.

  When there is a difference between the two screen data, the screen data transmission control unit 21 transmits the difference screen data indicating the difference to the client 10. The screen data holding unit 24 updates the screen data held in the storage device 25 as described above to the latest screen data transmitted from the screen data creation unit 22 as described above.

  The screen data transmission control unit 21 in the server 20 that holds the content detects an interruption by the drawing timer and transmits a screen data acquisition request to the screen data creation unit 22. The screen data transmission control unit compares the newly acquired screen data with the screen data held in the storage device 25, and checks the difference between the two screens. If there is a difference between the two screens, the screen data transmission control unit 21 transmits a request message indicating the difference screen data indicating the difference to the client 10. The screen data holding unit 24 updates the screen data held in the storage device 25 as described above to the latest screen data transmitted from the screen data creation unit 22 as described above. This difference occurs, for example, when the screen data is dynamically changed by a program included in the content, or by a user operation.

  When the client 10 receives the screen data as the difference information from the server 20 via the network 30, the client 10 updates the display screen based on the difference screen data and also indicates that the difference screen data has been received. Is transmitted to the screen data transmission control unit 21 of the server 20. When the difference screen data is transmitted using a reliable protocol (for example, TCP), the response message may be omitted.

  When the user performs a scroll operation on the client 10, the server 20 transmits the difference screen data corresponding to the scroll amount to the client 10 as described above. Regarding the transmission of the difference screen data corresponding to the scroll amount, as described above, a prefetching process for transmitting the difference screen data corresponding to the scroll amount obtained by increasing the actual scroll amount by a predetermined value may be applied.

  Further, the client 10 transmits a screen data read request to the server 20 in accordance with a user operation. As a result, when the screen data creation unit 22 of the server 20 needs to create screen data, the screen data creation unit 22 that has received the screen data read request increases the drawing processing interval until a predetermined time elapses. Based on the drawing processing interval widened as described above, the scheduler 23 widens the interval for instructing the screen data creation unit 22 to start drawing for a certain period of time. That is, as described above, the thinning process of the drawing process interval is performed.

(Second embodiment)
FIG. 7 is a diagram illustrating a second example of the functional configuration of the screen transfer system according to the embodiment of the present invention.
The system shown in FIG. 7 is a system that displays screen data on the client 10 using content (information necessary for creating screen data) transmitted by the content server 20a. In this system, the output function dividing server 40 is arranged between the client 10 and the content server 20 a, and screen data is created by the output function dividing server 40.

The output function dividing server 40 includes a screen data transmission control unit 41, a screen data creation unit 42, a scheduler 43, a screen data holding unit 44, and a storage device 45.
The client 10 transmits a connection request to the management server 50 before transmitting the content acquisition request. The management server 50 returns the access destination (for example, address and port number) of the output function division server to the client 10. The client 10 transmits a content acquisition request to the output function dividing server 40 via the network (NW) 30 based on the received access destination information. The content acquisition request includes a content server and information for identifying the content (for example, URI).

  The output function dividing server 40 transmits a content acquisition request to the content server 20a via the content acquisition request transmission / transfer unit 46 to obtain content. The output function dividing server 40 creates the latest screen data at the screen data creation unit 42 based on the content received from the content server 20a.

  The screen data created based on the content transmitted from the content server 20 a last time is held in the storage device 45 in the output function dividing server 40 by the screen data holding unit 44 in the output function dividing server 40. The screen data transmission control unit 41 includes the screen data created by the latest content transmitted from the content server 20a and the screen data held in the storage device 45 as described above, that is, from the content server 20a to the output function dividing server 40. The difference between the two screen data is checked by comparing with the screen data created by the content transmitted last time.

When there is a difference between the two screen data, the screen data transmission control unit 41 transmits the difference screen data indicating the difference to the client 10 according to the above. The screen data holding unit 44 updates the screen data held in the storage device 45 as described above to the screen data created based on the latest content transmitted from the content server 20a as described above.
Further, the output function dividing server 40 detects an interruption by the drawing timer, creates new screen data, and compares it with the screen data held in the storage device 45. When there is a difference between the two screen data, the screen data transmission control unit 41 transmits the difference screen data indicating the difference to the client 10 according to the above. This difference occurs, for example, when the content server 20a transmits new content by push processing, or the screen data dynamically changes by a program included in the content, or by a user operation.

  When the client 10 receives the difference screen data from the output function division server 40 via the network 30, the client 10 updates the display screen based on the difference screen data and also indicates that the difference screen data has been received. Is transmitted to the screen data transmission control unit 41 of the output function dividing server 40. When the difference screen data is transmitted using a reliable protocol (for example, TCP), the response message may be omitted.

  When the user performs a scroll operation on the client 10, as described above, the output function division server 40 transmits the difference screen data corresponding to the scroll amount to the client 10. Regarding the transmission of the difference screen data corresponding to the scroll amount, as described above, a prefetching process for transmitting the difference screen data corresponding to the scroll amount increased by a predetermined value may be applied.

  When the client 10 transmits a content acquisition request to the output function dividing server 40, the output function dividing server 40 that has received the content acquisition request receives the content necessary for creating screen data via the content acquisition request transfer unit 46. Is acquired from the content server 20a, and the screen data creation unit 42 creates screen data. The screen data creation unit that has received the content acquisition request widens the drawing processing interval until a predetermined time elapses. The scheduler 43 extends the interval for instructing the screen data creation unit 42 to start drawing based on the drawing processing interval widened as described above for a certain period of time. That is, as described above, the thinning process of the drawing process interval is performed.

(Third embodiment)
FIG. 8 is a diagram illustrating a third example of the functional configuration of the screen transfer system according to the embodiment of the present invention.
The system shown in FIG. 8 is a system in which screen data is displayed on the client 10 using Web content (information necessary for creating a screen) transmitted by the Web server 20b. The output function dividing server 40 is arranged between them, and screen data is created by the output function dividing server 40.

  Prior to transmitting the Web content acquisition request, the client 10 transmits a connection request for the output function dividing server to the management server 50, and information on the connection destination of the output function dividing server (for example, address and port number) from the management server 50. Receive. The client 10 transmits a Web content acquisition request to the output function dividing server 40 via the network (NW) 30. The Web content acquisition request includes information (for example, URL) for identifying the Web server and the Web content.

  The output function dividing server 40 transmits a Web content acquisition request to the content server 20a via the content acquisition request transmission / transfer unit 46, and obtains a response. The output function division server 40 creates the latest screen data by the screen data creation unit 42 based on the response from the Web content server 20b.

  The screen data created based on the web content transmitted last time from the web server 20 b is held in the storage device 45 in the output function dividing server 40 by the screen data holding unit 44 in the output function dividing server 40. The screen data transmission control unit 41 includes the screen data created by the latest web content transmitted from the web server 20b and the screen data held in the storage device 45 as described above, that is, the output function dividing server from the web server 20b. The screen data created based on the Web content previously transmitted to 40 is compared. If there is a difference between the two screen data, the difference screen data indicating the difference is transmitted to the client 10. This difference occurs, for example, when the web server 20b transmits new content by push processing, or the screen data changes dynamically by a program included in the web content, or by a user operation.

  The screen data holding unit 44 updates the screen data held in the storage device 45 as described above to the latest screen data as described above.

  The client 10 receives the difference screen data from the output function dividing server 40 via the network 30 and then updates the display screen based on the difference screen data and also indicates that the difference screen data has been received. Is transmitted to the screen data transmission control unit 41 of the output function dividing server 40. When the difference screen data is transmitted using a reliable protocol (for example, TCP), the response message may be omitted.

  When the user performs a scroll operation on the client 10, as described above, the output function division server 40 transmits the difference screen data corresponding to the scroll amount to the client 10. For the transmission of the difference screen data corresponding to the scroll amount, as described above, a prefetching process that transmits the difference screen data corresponding to the scroll amount obtained by increasing the actual scroll amount by a predetermined value may be applied. .

  Further, when the client 10 transmits a Web content acquisition request to the output function dividing server 40, the output function dividing server 40 that has received the Web content acquisition request is necessary for creating screen data via the content acquisition request transfer unit 46. The screen data creation unit 42 creates screen data after acquiring a valid content from the Web server 20b. The screen data creation unit 42 that has received the Web content acquisition request widens the drawing processing interval until a predetermined time elapses. The scheduler 43 increases the interval for instructing the screen data creation unit 42 to start drawing based on the drawing processing interval widened as described above for a certain period of time. That is, as described above, the thinning process of the drawing process interval is performed.

  In the embodiment described above, since the minimum screen data can be transmitted in consideration of the update of the screen data based on the user operation etc., the bandwidth to be used is reduced while maintaining the response performance to the screen update. It becomes possible to do.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  In addition, the method described in the embodiment is, for example, a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), optical disk (CD-ROM, DVD) as programs (software means) that can be executed by a computer (computer). , MO, etc.), a semiconductor memory (ROM, RAM, flash memory, etc.) or the like, or can be transmitted and distributed via a communication medium. The program stored on the medium side includes a setting program that configures software means (including not only the execution program but also a table and data structure) in the computer. A computer that implements this apparatus reads a program recorded on a recording medium, constructs software means by a setting program as the case may be, and executes the above-described processing by controlling the operation by this software means. The recording medium referred to in this specification is not limited to distribution, but includes a storage medium such as a magnetic disk or a semiconductor memory provided in a computer or a device connected via a network.

  DESCRIPTION OF SYMBOLS 10 ... Client, 20 ... Server, 20a ... Content server, 20b ... Web server, 21, 41 ... Screen data transmission control part, 22, 42 ... Screen data creation part, 23, 43 ... Scheduler, 24, 44 ... Screen data holding , 25, 45 ... storage device, 46 ... content acquisition request transmission / transfer unit, 30 ... network, 40 ... output function division server, 50 ... management server.

Claims (7)

A screen data creation unit that creates the latest screen data at predetermined intervals;
An acquisition unit for acquiring the created latest screen data;
A holding unit for holding screen data acquired by the acquisition unit last time;
A transmission control unit that transmits a difference between the acquired latest screen data and the held previously acquired screen data to a client device;
The screen data creation unit
When a screen data read request is generated in the client device, the screen transfer server device extends the screen data creation cycle until a predetermined time elapses after receiving the request. A screen data creation unit that creates the latest screen data at predetermined intervals;
An acquisition unit for acquiring the created latest screen data;
A holding unit for holding screen data acquired by the acquisition unit last time;
A transmission control unit that transmits a difference between the acquired latest screen data and the held previously acquired screen data to a client device;
The transmission control unit
When the screen on the client device is scrolled, the actual scrolling amount is changed from the operation for scrolling on the screen on the client device until the screen data corresponding to the difference reaches the client device. Based on the scroll amount increased by a predetermined scroll amount expected to be scrolled by the operation, the screen data corresponding to the difference between the screen before scrolling and the screen after scrolling is stored in the client device. A screen transfer server device characterized by transmitting. The difference is in the rectangular area defined on the screen, according to claim 1, characterized in that a screen data corresponding to the difference between the most recent screen data and the retained last acquired screen data to which the acquired or 3. The screen transfer server device according to 2. The difference is in the bit unit on the screen, according to claim 1 or 2, characterized in that the screen data corresponding to the difference between the most recent screen data and the retained last acquired screen data to which the acquired Screen transfer server device. The transmission control unit
When the screen on the screen of the client device is scrolled, screen data corresponding to the difference between the screen before scrolling and the screen after scrolling is obtained based on the scroll amount obtained from the information acquired from the client device. The screen transfer server device according to claim 1, wherein A method applied to a screen transfer server device,
The screen transfer server device
Create the latest screen data every predetermined cycle,
Get the latest screen data created,
Holds the previously acquired screen data,
Send the difference between the acquired latest screen data and the held screen data to the client device ,
When a screen data read request is generated in the client device, a screen transfer method is characterized in that after the request is received, a screen data creation cycle is extended until a predetermined time elapses . A method applied to a screen transfer server device,
The screen transfer server device
Create the latest screen data every predetermined cycle,
Get the latest screen data created,
Holds the previously acquired screen data,
Send the difference between the acquired latest screen data and the held screen data to the client device,
When the screen on the client device is scrolled, the actual scrolling amount is changed from the operation for scrolling on the screen on the client device until the screen data corresponding to the difference reaches the client device. Based on the scroll amount increased by a predetermined scroll amount expected to be scrolled by the operation, the screen data corresponding to the difference between the screen before scrolling and the screen after scrolling is stored in the client device. A screen transfer method characterized by transmitting.

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