JP4140728B2 - Management server and program - Google Patents

Description

  The present invention relates to a network communication system for exchanging data such as messages between clients.

  Conventionally, in a network system in which data communication is performed using a request / response communication protocol such as HTTP, for example, when data such as a message is exchanged between clients via a server, the client accesses and updates the server every predetermined time. The presence or absence of information was confirmed. A method in which a client accesses a server at every predetermined time to acquire / update information is generally called a polling method.

  For example, a case where messages are exchanged between client A and client B will be described as an example. After client B sends a request to server at time T1, client A registers message data for client B in the server. The client B transmits a request to the server at the next access time T2 (= time T1 + Δt), and acquires message data registered in the server.

  In the system as described above, if an attempt is made to exchange data between clients in a manner closer to real time, requests from the client to the server are frequently generated. In this case, there is a problem that the amount of communication packets increases and the network load increases. Further, since communication occurs even when information is not updated on the server side, there is a possibility that communication efficiency may be reduced due to generation of useless packets (empty packets).

  Further, there is an instant message function or the like as one of the Internet functions that enables highly real-time data communication (message exchange) between clients. Instant messages are mainly used in personal computers due to the nature of exchanging messages between clients connected to the network, and for use in mobile terminals, mobile phones, etc. that cannot communicate depending on the situation. It was not suitable. For example, since a message cannot be transmitted / received when a mobile terminal or the like is out of the communication range and is in an offline state, a message transmitted to a user of the mobile terminal or the like is wasted. there were.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a management server capable of exchanging messages in real time between clients and improving communication efficiency.
In addition, the present invention provides a management server or the like that can improve the real-time property in data exchange between clients and reduce the network load in a network system using a request / response communication protocol. For other purposes.
Another object of the present invention is to provide a management server that enables real-time communication functions such as instant messages to be used between portable terminals and the like.

In order to achieve the above object, the management server according to the first aspect of the present invention provides:
A management server connected via a network to a plurality of clients that can communicate with each other via a network;
Storage means for storing status information indicating the communication state of each client;
According to the communication request from each client, means the client notifies the polling time before sending the next communication request to the client,
Determine whether it has received the communication request from the client within the polling time notifies each client, if it has not received, the status information of the client in the storage unit, the client first incommunicable Means for setting the status,
For the client whose status information in the storage means is set to the first communication disabled state, it is determined whether a communication request has been received from the client within a predetermined time . If the status information of the client indicates that the client is in a communicable state and is not received, the client is in the second communication disabled state in the status information of the client in the storage means. A means to set the effect and end the session with the client;
Means for transmitting status information of the designated other client stored in the storage means to the one client in response to a communication request designating another client from one of the plurality of clients ; ,
It is characterized by providing.

  According to the present invention, since the communication state of the client can be grasped and managed by the management server, the real-time data communication function can be used even by the client whose communication state changes. In addition, since status information indicating the communication state can be output and supplied to other clients or the like, useless message transmission or the like can be reduced.

When the status information receives a message for a client for which the client is set to be in the first communication disabled state , the message is retained, and when the communication with the client is resumed, the retained message May be supplied to the client.

  The client may include at least one of a mobile terminal and a mobile phone.

The program according to the second aspect of the present invention is:
A computer connected via a network to a plurality of clients capable of communicating with each other via the network ;
Storage means for storing status information indicating the communication state of each client;
According to the communication request from each client, means the client notifies the polling time before sending the next communication request to the client,
Determine whether it has received the communication request from the client within the polling time notifies each client, if it has not received, the status information of the client in the storage unit, the client first incommunicable Means for setting the status,
For the client whose status information in the storage means is set to the first communication disabled state, it is determined whether a communication request has been received from the client within a predetermined time . If the status information of the client indicates that the client is in a communicable state and is not received, the client is in the second communication disabled state in the status information of the client in the storage means. Means to end the session with the client by setting
Means for transmitting status information of the designated other client stored in the storage means to the one client in response to a communication request designating another client from one of the plurality of clients ;
To function as.

  According to the present invention, the real-time property in data communication such as message exchange between clients can be improved, and the communication efficiency can be improved.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing the configuration of a network communication system according to the first embodiment of the present invention.
As shown in the figure, this network communication system includes a client 11 and a management server 13 connected to each other via a network 10.

  The network 10 includes a mobile communication network, a telephone line, the Internet, and the like, and enables information to be transmitted and received between the client 11 and the management server 13.

The client 11 includes a mobile terminal, a mobile phone, a personal computer, and the like that include a control unit 111, a storage unit 112, a display unit 113, an input unit 114, a communication control unit 115, and the like. Communicate between the two.
As illustrated in FIG. 2, the control unit 111 of the client 11 logically implements a browser unit 111 a and a request control unit 111 b by executing an operation program or the like stored in the storage unit 112.

The browser unit 111a has a conventional browser function, and performs processing for transmitting request information to the server, processing for receiving response information from the server, and the like in conjunction with the request control unit 111b.
The request control unit 111b refers to predetermined information (polling interval information) included in the response information received from the management server 13, and sends the next request information to the management server 13 at the polling interval indicated by the information. To control.

  An example of request information transmitted from the client 11 to the management server 13 is shown in FIG. This request information includes data such as protocol version, request command, control flag, number of receivable events, AckID, and request event. Among these, the control flag includes an immediate return flag indicating whether or not to immediately return a response corresponding to the request. For example, an immediate return flag is set to “on” for a request for which a response should be returned immediately (for example, “login request”, “setting change request”, etc.), and an immediate return flag is set for other requests. Set to “Off”.

An operation program executed by the storage unit 112 and the control unit 111 and various data necessary for processing are stored.
The display unit 113, a CRT, and a liquid crystal display are included, and various screen displays are performed in accordance with instructions from the control unit 111.
The input unit 114 includes an input device such as a mouse and a keyboard, and notifies the control unit 111 of input data.
The communication control unit 115 is for performing data communication with the management server 13 or the like via the network 10.

  As illustrated in FIG. 4, for example, the management server 13 includes a computer or the like that includes a control unit 131, a storage unit 132, and a communication control unit 133.

  The control unit 131 logically implements the web server unit 131a, the response control unit 131b, and the like by executing an operation program or the like stored in the storage unit 132.

  The web server unit 131a has the same function as the conventional web server, and in response to the response control unit 131b, response information including polling interval information for instructing the client 11 the next polling interval Process to send. Further, when the web server unit 131a receives the request information, the web server unit 131a does not immediately reply to the response information, but transmits the response information to the client 11 at a predetermined timing such as when a predetermined event occurs or immediately before timeout. To do. For request information that is set to return response information immediately, response information is returned immediately.

  Further, the web server unit 131 a stores event information (communication record) indicating the date and time of occurrence, event contents, and the like in the event database 132 a of the storage unit 132 for events (various key operations and the like) that have occurred in each client 11.

  In response to reception of request information from the client 11, the response control unit 131b determines a polling interval to be notified to the client 11, and passes polling interval information indicating this to the web server unit 131a. For example, the polling interval determination method refers to the event information stored in the event database 132a, and information such as the event occurrence frequency in the client 11 of the request transmission source and the event occurrence frequency of the communication partner of the request transmission source client. Based on the above, a time interval with good communication efficiency is calculated by operations research or the like. For example, a multivariate analysis may be performed on a user's past usage pattern, and an optimal polling interval may be determined using the result.

  An example of response information transmitted from the management server 13 to the client 11 is shown in FIG. This response information includes, for example, data such as response ID, response code, polling interval information, session ID length, session ID, number of event / request results, event / request results.

  The storage unit 132 stores an operation program executed by the control unit 131 and various data necessary for processing. In addition, the storage unit 132 includes an event database 132a that stores information (event information) on events that have occurred in each client.

  The communication control unit 133 is for performing data communication with the client 11 and the like via the network 10.

  Next, the operation of the network communication system according to the first embodiment will be described focusing on the features of the present invention.

First, the request transmission process in the client 11 will be described with reference to the flowchart of FIG.
First, the client 11 generates request information corresponding to the user's input operation and transmits it to the management server 13 (step S1).

When the response information corresponding to the transmitted request information is received from the management server 13, the polling interval information included in the response is stored in a predetermined area of the storage unit (step S2).
Then, processing corresponding to the content of the received response information (for example, displaying HTML data if the response information is attached) is performed (step S3).

  Then, after the polling time indicated by the polling interval information has elapsed (step S4), the process returns to step S1, and repeats the process of generating the next request information and transmitting it to the management server 13 (steps S1 to S4).

  Note that the timing of starting and ending the request transmission process is arbitrary. For example, the request transmission process may be started when logging in to the management server 13 or when a predetermined input operation (for example, selecting “Message exchange” from the operation menu) Alternatively, the process may be terminated when logging out or a predetermined input operation (for example, selecting “end message exchange” from the operation menu).

Next, the response transmission process in the management server 13 will be described with reference to the flowchart of FIG.
When the management server 13 receives the request information from the client 11, the management server 13 refers to the immediate return flag included in the request information (step S 10), and notifies the request source when it is determined that the setting content is “off”. Determine if there is already an event to be performed.
If there is no event to be notified (step S11: N), it waits for the occurrence of a predetermined event (for example, data update by the communication partner) until just before the HTTP session timeout (step S12).

  If it is determined in step S11 that there is an event to be notified, or if it is just before the timeout in step S12, processing for calculating the polling time for the requesting client is performed (step S13). Then, request information including polling interval information indicating the calculated polling time is transmitted to the requesting client 11 (step S14), and this process is terminated.

  In step S10, if the immediate return flag included in the request information is set to “on”, the polling interval calculation process is continued (step S13), and the response information is returned. (Step S14), the process is terminated.

Next, the flow of processing between the devices in this system will be described with reference to FIG. 8 by taking as an example the case where user A and user B exchange messages.
First, for example, the user B transmits a login request req1 to the management server 13 using the client 11B (L1).
When receiving the login request req1 from the client 11B, the management server 13 calculates a polling interval td0 for the client 11B, and transmits a login completion notification res1 including this information to the client 11B (L2).

On the other hand, the user A also transmits a login request req2 to the management server 13 using the client 11A (L3).
The management server 13 calculates a polling interval td1 for the client 11A, and transmits a login completion notification res2 including this information to the client 11A (L4). For example, at this time, the user A is also notified that the user B is logging in.

On the client 11B side, when the notified polling interval td0 has elapsed, the request information req3 is transmitted to the management server 13 (L5).
The management server 13 does not immediately return a response to the received request req3, but waits until an event occurs or immediately before a timeout.

At this time, for example, before the polling interval td1 elapses, the client 11A transmits a presence change request req4 to the management server 13 in accordance with an input operation by the user A (or automatically) (L6).
When the management server 13 receives the presence change request req4 from the client 11A, it calculates a polling interval td2, transmits a change completion notification res4 including this information to the client 11A (L7), and this event (presence change of the user A) ) To send the response information res3 (corresponding to the request req3) to notify the client 11B (L8). This response res3 includes information on the polling interval td3.

  Next, it is assumed that the client 11A transmits a message req5 to the user B according to the input operation by the user A (L9). The management server 13 updates / stores information on a message from the user A to the user B. Also, the management server 13 does not immediately return a response to the received request req5, but waits until an event occurs or immediately before a timeout.

On the client 11B side, when the notified polling interval td3 has elapsed, the request information req6 is transmitted to the management server 13 (L10).
At this time, since an event to be notified to the client 11B (message from the user A) has already occurred, the management server 13 sends a message transmission completion notification res5 (corresponding to the request req5 and includes information on the polling interval td4). Is transmitted to the client 11A (L11), and a message res6 (including information on the polling interval td5) from the user A is transmitted to the client 11B (L12).

On the client 11A side, when the notified polling interval td4 has elapsed, the request information req7 is transmitted to the management server 13 (L13). On the client CB side, when the notified polling interval td5 elapses, the request information req8 is transmitted to the management server 13 (L14). The management server 13 receives these requests and transmits corresponding responses to the clients 11B and 11C.
Thereafter, the exchange of requests and responses as described above is continued between the clients 11A and 11B and the management server 13 until the communication is completed.

  As described above, according to the first embodiment of the present invention, the management server 13 instructs the client 11 on a suitable polling interval, causes the client 11 to send a request at this time interval, and the management server 13 In 13, by transmitting a response at the timing such as the occurrence of an event or immediately before a timeout, the network load can be reduced and the communication efficiency can be improved while improving the real-time property of data communication between clients.

The data structure of the request and response in the first embodiment is an example, and is not limited to this and is arbitrary.
The method for determining the polling interval is arbitrary, and various calculation methods, analysis methods, and the like can be applied.
Further, in the client 11, before the request Rn based on the notified polling time is transmitted, if the user generates a request and transmits it to the management server 13, the transmission of the request Rn may be stopped.

(Second Embodiment)
Next, a network communication system according to the second embodiment of the present invention will be described. This network communication system is a system for directly exchanging messages between terminals connected to the Internet. Such a message exchange function is generally called instant message.

FIG. 9 is a diagram showing a configuration of a network communication system according to the second embodiment of the present invention.
As shown in the figure, this network communication system includes a client 16 and a management server 17 connected to each other via a network 15.

  The network 15 is composed of a mobile communication network, a telephone line, the Internet, and the like, and enables information to be transmitted and received between the client 16 and the management server 17.

  The client 16 includes a mobile terminal, a mobile phone, and the like including a control unit 161, a storage unit 162, a display unit 163, an input unit 164, a communication control unit 165, and the like. Communicate.

  As illustrated in FIG. 10, the control unit 161 of the client 16 logically implements a message transmission / reception unit 161 a and a session management unit 161 b by executing an operation program or the like stored in the storage unit 162.

  The message transmission / reception unit 161a generates a message addressed to another user according to an input operation by the user, transmits a message to the management server 17, and receives a message addressed to the user from the management server 17. Perform processing.

  The session management unit 161b stores information such as a polling interval value and a session timeout value notified from the management server 17 in the storage unit 162 after logging in to the management server 17 in accordance with an input operation by the user. The next communication request is transmitted to the management server 17 at the polling interval indicated by. In addition, the session management unit 161b communicates with the management server 17 at least once within the time indicated by the session timeout value.

The storage unit 162 stores an operation program executed by the control unit 161 and various data necessary for processing.
The display unit 163 includes a display device such as a CRT or a liquid crystal display, and performs various screen displays according to instructions from the control unit 161.
The input unit 164 includes an input device such as a mouse and a keyboard, and notifies the control unit 161 of input data.
The communication control unit 165 is for performing data communication with the management server 17 via the network 15.

  As shown in FIG. 11, for example, the management server 17 includes a computer or the like that includes a control unit 171, a storage unit 172, and a communication control unit 173.

  The control unit 171 logically implements a message exchange control unit 171a, a connection state check unit 171b, and the like by executing an operation program or the like stored in the storage unit 172.

The message exchange control unit 171a performs processing for exchanging messages between logged-in users. Specifically, a process for receiving a message addressed to another login user from the login user and supplying the message in response to a communication request or the like from another login user (message destination user) is performed.
In this message exchange process, the message exchange control unit 171a checks the communication status of the destination user with reference to the connection status information of each user (client 16) stored in the connection status database 172a of the storage unit 172.

  For example, as shown in FIG. 12, this connection status information includes, for each user, a user ID, status, login time, last communication time, temporary unavailable time (time when the status is set to “temporarily unavailable”), and the like. Contains data. Among these, for example, information indicating the communication state of the client 16 such as “communication enabled”, “temporarily disabled”, and “communication disabled” is set in the status. The last communication time is updated each time a communication request is received from the client 16.

  When the status of the message destination user is “temporarily disabled”, the message exchange control unit 171a queues the message in a predetermined area of the storage unit 172 for each user. Then, when the “temporarily disabled” status is resolved, the queued message is supplied to the client 16 of the user. In addition, when the “temporarily disabled state” status is changed to “communication disabled state (offline)”, “transfer message by e-mail”, “send to sender” according to the countermeasures set in advance by the user Predetermined processing such as “Prompt to resend message” is performed.

  The connection state check unit 171b performs processing for checking and managing the connection state of the client 16 of each user. Specifically, the polling interval value and the session time value are notified to each client 16 logged into the management server 17. For each logged-in user, the last communication time in the connection state information is updated every time there is a communication request. For each logged-in user, it is checked whether there is a communication request to the management server 17 within the time indicated by the polling interval value from the time of the last communication, and if there is no communication request within the polling time, the status of that user Is set to “temporarily disabled”. Further, the connection state check unit 171b checks whether or not there is a communication request to the management server 17 within the time indicated by the session time value when the status is set to “temporarily disabled” for each login user, When there is no communication request within the session time, the login session of the client 16 is terminated and the status of the user is set to “communication disabled state”. Further, when a communication request is received from the client 16 of the user whose status is “temporarily disabled”, the connection status check unit 171b returns the status to “communicable”.

  In addition, the connection state check unit 171 b supplies information such as the status in the connection status information of the login user to the client 16 that has issued a communication request to the management server 17. The status supply method is arbitrary. For example, a status inquiry request may be received together with user designation, and the status of the designated login user may be supplied to the requesting client 16. The status of a plurality of users belonging to a group may be notified in response to a communication request from a user belonging to the group.

The storage unit 172 stores an operation program executed by the control unit 171 and various data necessary for processing.
The storage unit 172 includes a connection state database 172a that stores connection state information (FIG. 12), and a user database 172b that stores predetermined user information (user ID, user name, mail address, etc.).

  The communication control unit 173 is for performing data communication with the client 16 and the like via the network 10.

The operation of the network communication system according to the second embodiment will be described below with a focus on the features of the present invention.
First, connection state check processing in which the management server 17 checks the connection state for each login user will be described with reference to the flowchart of FIG. This process is executed at a timing such as every predetermined time.

The management server 17 reads the connection status information of one login user from the connection status database 172a (step S21).
Then, the status of the read connection state information is determined (step S22). For example, if “communication is possible”, it is determined whether the polling time has elapsed from the last communication time (step S23). If the polling time has elapsed, the status is changed to “temporarily disabled” (step S24).

  If the status of the read connection state information is “temporarily disabled” in step S22, the management server 17 determines whether the session timeout time has elapsed from the temporarily disabled time (step S25). The client 16 terminates the login session of the client 16 and changes its status to “communication disabled” (step S26).

If it is determined in step S23 that the polling time has not elapsed, the status is changed in step S24. Then, if it is determined in step S25 that the session timeout time has not elapsed, the status is determined in step S26. After the change, it is determined whether or not the processing has been completed for all the logged-in users (step S27), and the processing of steps S21 to S27 is repeated until the processing is completed for all the logged-in users.
By this connection state check process, the management server 17 can grasp the communication states of all the logged-in users.

Next, a specific processing flow when the management server 17 grasps the communication state of the client 16A of a login user A will be described with reference to FIG.
For example, when the user A inputs a user name and password to the client 16A and presses a predetermined login button, the client 16A transmits login information based on the input data to the management server 17 (L21).

  The management server 17 receives login information from the client 16, performs predetermined login authentication, and starts a session with the client 16A. Then, the management server 17 notifies the client 16A of information such as a session timeout value and a polling value together with a login success response (L22).

  The client 16A stores the session timeout value and polling value received from the management server 17. When the notified polling time has elapsed, the client 16A transmits a communication request for acquiring update information (for example, a new message addressed to the user A) to the management server 17 (L23).

  In response to a communication request from the client 16A, the management server 17 updates the connection state information of the client 16A in the connection state database 172a at the time of the final communication, and updates information regarding the user A and polling for the next polling The value and the like are notified to the client 16A (L24).

The client 16A stores the polling value received from the management server 17. Then, after the elapse of the notified polling time, an attempt was made to send a communication request to the management server 17, but it was assumed that communication with the management server 17 could not be made because the communication request was out of the communication range.
The management server 17 sets the status in the connection status information to “temporarily disabled” because there is no communication request for the client 16A within the polling time from the previous communication (L25). Then, for example, another user who has made a communication request may be notified that the client 16A is in a “temporarily disabled state”.

For example, when the client 16A is in the communication range, communication is retried, and the communication request is transmitted to the management server 17 before the session timeout (L26).
Since the client 16A has polled before the session time-out, the management server 17 changes the status of the client 16A to “communication enabled” (L27), and notifies the client 16A of a polling value for the next polling (L28).

Next, it is assumed that the client 16A cannot communicate with the management server 17 because it is out of the communication range again, for example.
The management server 17 sets the status in the connection status information to “temporarily disabled” because there is no communication request for the client 16A within the polling time from the previous communication (L29). If the session time-out occurs without a communication request, the status of the client 16A is set to “communication disabled” and the session is terminated (L30).

  In this way, according to the second embodiment of the present invention, the communication state of the client 16 can be grasped and managed by the management server 17, so that an instant message function etc. Real-time data communication function can be used. Further, each user can confirm the communication state of the other party and transmit a message, so that useless message transmission can be reduced.

In the second embodiment, the system using the instant message function has been described. However, the scope of application of the present invention is not limited to this, and the present invention can be applied to a system using various real-time data communication functions. .
The client 16 is not limited to a mobile terminal, a mobile phone, or the like, and may include a personal computer or the like.
Moreover, the data structure of connection state information is an example, and is not limited to this, but is arbitrary.

Moreover, in the said 1st and 2nd embodiment, the structure of each apparatus and DB can be changed arbitrarily.
Each server may be composed of a plurality of computer systems operating in cooperation with each other, and the functions of the servers may be integrated by a single computer system.

The system of the present invention can be realized using a normal computer system, not a dedicated system. For example, a program for executing the above operation is stored in a computer-readable recording medium (FD, CD-ROM, DVD, etc.) and distributed, and the program is installed in the computer to execute the above processing. Each client, management server, and the like may be configured. Further, it may be stored in a disk device included in a server device on a network such as the Internet, and may be downloaded onto a computer, for example, superimposed on a carrier wave.
Further, when the OS realizes the above functions by sharing the OS or jointly with the OS and the application, only the part other than the OS may be stored and distributed in a medium, or may be superimposed on a carrier wave to a computer. You may download it.

It is a figure which shows the structure of the network communication system which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the client used with the network communication system of FIG. It is a figure which shows an example of the data structure of request information. It is a figure which shows the structure of the management server used with the network system of FIG. It is a figure which shows an example of the data structure of response information. It is a flowchart for demonstrating the request transmission process in a client. It is a flowchart for demonstrating the response transmission process in a management server. It is a figure for demonstrating concretely the flow of the process between each apparatus in the system which concerns on 1st Embodiment. It is a figure which shows the structure of the network communication system which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the client used with the network communication system of FIG. It is a figure which shows the structure of the management server used with the network system of FIG. It is a figure which shows an example of the data structure of connection state information. It is a flowchart for demonstrating the connection state check process in a management server. It is a figure for demonstrating concretely the flow of the process between each apparatus in the system which concerns on 2nd Embodiment.

Explanation of symbols

10, 15 Network 11, 16 Client 13, 17 Management server 111, 161 Control unit 112, 162 Storage unit 113, 163 Display unit 114, 164 Input unit 115, 165 Communication control unit 111a Browser unit 111b Request control unit 161a Message transmission / reception unit 161b Session management unit 131, 171 Control unit 132, 172 Storage unit 133, 173 Communication control unit 131a Web server unit 131b Response control unit 132a Event DB
171a Message exchange control unit 171b Connection state check unit 172a Connection state DB
172b User DB

Claims (4)

A management server connected via a network to a plurality of clients that can communicate with each other via a network;
Storage means for storing status information indicating the communication state of each client;
According to the communication request from each client, means the client notifies the polling time before sending the next communication request to the client,
Determine whether it has received the communication request from the client within the polling time notifies each client, if it has not received, the status information of the client in the storage unit, the client first incommunicable Means for setting the status,
For the client whose status information in the storage means is set to the first communication disabled state, it is determined whether a communication request has been received from the client within a predetermined time . If the status information of the client indicates that the client is in a communicable state and is not received, the client is in the second communication disabled state in the status information of the client in the storage means. A means to set the effect and end the session with the client;
Means for transmitting status information of the designated other client stored in the storage means to the one client in response to a communication request designating another client from one of the plurality of clients ; ,
A management server comprising: When the status information receives a message for a client for which the client is set to be in the first communication disabled state , the message is retained, and when the communication with the client is resumed, the retained message To the client,
The management server according to claim 1. The client includes at least one of a mobile terminal and a mobile phone.
The management server according to claim 1 or 2, characterized by the above. A computer connected via a network to a plurality of clients capable of communicating with each other via the network ;
Storage means for storing status information indicating the communication state of each client;
According to the communication request from each client, means the client notifies the polling time before sending the next communication request to the client,
Determine whether it has received the communication request from the client within the polling time notifies each client, if it has not received, the status information of the client in the storage unit, the client first incommunicable Means for setting the status,
For the client whose status information in the storage means is set to the first communication disabled state, it is determined whether a communication request has been received from the client within a predetermined time . If the status information of the client indicates that the client is in a communicable state and is not received, the client is in the second communication disabled state in the status information of the client in the storage means. Means to end the session with the client by setting
Means for transmitting status information of the designated other client stored in the storage means to the one client in response to a communication request designating another client from one of the plurality of clients ;
Program to function as.

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