JP2004199307A - Session identifier management system, session identifier management method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate prediction of a session identifier in a system establishing a session between a host computer and a terminal to execute communication. <P>SOLUTION: When connection is required from the terminal 2B, the host computer 1 generates a session object 421B which manages information about the terminal 2B and a session identifier B for uniquely identifying the session object 421B. The host computer 1 adds the session identifier B to the session object 421B, stores the session object 421B into a session object storage area 42, and transmits the session identifier B to the terminal 2B. When a message is sent from the terminal 2B being in a session connection state, the host computer 1 generates a new session identifier B1, replaces the session identifier B in the session object 421B with the new session identifier B1, and transmits the new session identifier B1 to the terminal 2B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a session identifier management technique in a host computer that establishes a logical communication path (session) with a plurality of terminals and performs communication, and in particular, makes it very difficult to predict a session identifier. The present invention relates to session identifier management technology.
[0002]
[Prior art]
In an online system composed of a terminal and a host computer connected via a network, the number of terminals and the amount of communication are steadily increasing with the spread of the client-server model or the three-layer model. Often become. In order to solve such a problem, it has been conventionally performed to divide a logical communication path into two layers (a connection layer and a session layer) and to share and use a connection in a plurality of sessions. The prior art will be described in detail below.
[0003]
At the time of session connection with the terminal, the host computer manages information relating to the terminal (the necessary information may be designed according to the system, and may include, for example, a terminal protocol and a port number). A session identifier for uniquely identifying the session object is generated. Thereafter, a session identifier is added to the session object and stored in the storage area, and the session identifier is transmitted to the terminal via the network.
[0004]
Thereafter, when transmitting the message to the host computer, the terminal adds the session identifier sent from the host computer to the message.
[0005]
When a message to which a session identifier is added is sent from the terminal, the host computer searches the storage area and acquires a corresponding session object. Then, business processing is performed according to the acquired session object and the message from the terminal.
[0006]
With the above control, the host computer can recognize the real terminal of the request source even for a connection that has been temporarily disconnected and reconnected, a different connection, or a message that has passed through a completely different relay device. That is, the independence of the connection and the session is enhanced, and the network resources can be effectively used.
[0007]
By the way, in the above-mentioned conventional technology, it is important to prevent the session identifier from being easily guessed in order to prevent unauthorized access due to spoofing. As a conventional technique that makes it difficult to estimate a session identifier, a technique of generating a session identifier including the generation time when a session identifier is generated at the time of session connection is known (for example, see Patent Document 1).
[0008]
[Patent Document 1]
JP 2000-163346 A
[0009]
[Problems to be solved by the invention]
However, the conventional technique described in Patent Literature 1 continuously uses the same session identifier while in the session connection state, so that the risk of predicting the session identifier in use is sufficiently low. It is difficult to reduce. That is, since the same session identifier is used for a long time, there is a risk that the session identifier is predicted.
[0010]
Therefore, an object of the present invention is to make it extremely difficult to predict a session identifier, so that the risk of unauthorized access can be extremely reduced.
[0011]
[Means for Solving the Problems]
A first session identifier management device according to the present invention achieves the above object,
For each terminal in the session connection state, a session object that manages information about the terminal is managed using a session identifier that uniquely identifies the session object, and a message with a session identifier added is sent from the terminal. In the case, a session identifier management device in a host computer that searches for a session object specified by a session identifier added to the message,
When the terminal is in the session connection state, a means is provided for changing a session identifier that specifies a session object of the terminal, and transmitting the changed session identifier to the terminal.
[0012]
The second session identifier management device according to the present invention is the first session identifier management device.
When the message is sent from the terminal, the means changes a session identifier for specifying a session object of the terminal.
[0013]
More specifically, the third session identifier management device according to the present invention includes:
A session identifier management device in a host computer that establishes a session with a terminal and performs communication,
At the time of a connection request from a terminal, a session object for managing information on the terminal is generated and a session identifier generation request is output, and a session identifier returned in response to the session identifier generation request is added to the session object. Session object generating means for storing in a storage area and transmitting to the terminal;
When a message with a session identifier added thereto is sent from a terminal, a session object specified by the added session identifier is searched from a storage area and a session identifier generation request is output, and the message is added to the message. A session identifier in the session object specified by the current session identifier to a session identifier returned in response to the session identifier generation request, and further transmitting the returned session identifier to the terminal. When,
Session identifier generating means for generating a new session identifier in response to the session identifier generation request, and returning the generated session identifier to the requestor.
[0014]
A fourth session identifier management device according to the present invention is a third session identifier management device,
An identifier counter, and
The apparatus is characterized in that the session identifier generation means increments the identifier counter in response to a session identifier generation request, and generates a session identifier including the incremented count value of the identifier counter.
[0015]
A fifth session identifier management device according to the present invention is the third session identifier management device,
The session identifier generation means may be configured to generate a session identifier including a current time in response to a session identifier generation request.
[0016]
A sixth session identifier management device according to the present invention is the fifth session identifier management device.
Wireless terminal deletion means for deleting a session object of a terminal in a non-communication state for a predetermined time or more based on a session identifier added to each session object stored in the storage area. .
[0017]
[Action]
Since the session identifier is changed even during the session connection, the prediction of the session identifier can be made extremely difficult. As a result, the risk of unauthorized access impersonating another terminal can be extremely reduced. The session identifier is changed, for example, every time a message is sent from the terminal. As the session identifier, for example, one that includes the time at which the message was sent, or one that is incremented each time a message is sent For example, one including the value of the identifier counter to be used can be used. Also, by including the time when the message was sent in the session identifier, a terminal in a non-communication state for a predetermined time or more is detected based on the session identifier, and a session object corresponding to the terminal is stored in the storage area. Can be deleted from.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
[Configuration of the embodiment]
Referring to FIG. 1, one embodiment of the present invention includes a host computer 1 and terminals 2A, 2B, and 2C physically connected to the host computer 1 via a network 3. A logical communication path (session) is established between the host computer 1 and the terminals 2A, 2B, 2C, and they communicate with each other.
[0020]
The host computer 1 includes a memory 4, a communication control unit 5, a terminal connection processing unit 6, a business processing unit 7, a terminal disconnection processing unit 8, a session identifier generation unit 10, a session object generation unit 11, It comprises an object searching means 12, a session object deleting means 13, and a recording medium K1.
[0021]
The memory 4 includes a session object management table 41, a session object storage area 42, and an identifier counter 43.
[0022]
The session object storage area 42 stores a session object that manages information about each terminal in a connected state. In the example of FIG. 1, a session object 421A for managing information about the terminal 2A and a session object 421B for managing information about the terminal 2B are stored.
[0023]
The session object management table 41 is a table for managing the session objects 421A and 421B stored in the session object storage area 42, and has an entry number and a session object pointer as items. The session object management table 41 shown in FIG. 1 has n entries, and can manage session objects relating to a maximum of n terminals. The item of the session object pointer of each entry expresses a pointer relationship by an arrow extending from a black circle. Open circles represent empty entries. For example, entry 2 stores a pointer to the session object 421B. Entry 1 is an empty entry. By using the session object management table 41 having such an array configuration, the table reference person can directly (in a very short time) obtain a session object pointer by accessing the array by specifying an entry number. .
[0024]
The session identifier generation means 10 has a function of generating a session identifier for uniquely identifying a session object in response to a session identifier generation request from the session object generation means 11 or the session object search means 12, and a function of generating the generated session identifier. Has a function to return to the requester. As shown in FIG. 5, the session identifier includes an entry number and a value of an identifier counter. Illustrated as an example is a session identifier with an entry number = 2 and an identifier counter = 5.
[0025]
The session object generation means 11 generates a session object and stores it in the session object storage area 42, and stores a pointer to the session object stored in the session object storage area 42 in an empty entry in the session object management table 41. To add a session identifier returned from the session identifier generation unit 10 to a session object stored in the session object storage area 42 or a function of outputting a session identifier generation request to the session identifier generation unit 10. Has functions etc.
[0026]
The session object search means 12 searches the session object management table 41 based on the session identifier added to the message from the terminal and obtains a pointer to the corresponding session object. A session identifier generation request for the session identifier, a function of replacing the session identifier in the session object pointed to by the obtained session object pointer with the session identifier returned from the session identifier generation means 10, and a function of updating the session identifier after updating the session identifier. It has a function of returning objects to the business processing means 7 and the like.
[0027]
The session object deletion means 13 searches the session object management table 41 based on the session identifier added to the disconnection request from the terminal and obtains a pointer to the corresponding session object. It has a function of deleting the session object pointed by from the session object storage area 42, a function of rewriting the corresponding entry on the session object management table 41 to an empty entry, and the like.
[0028]
Access to the session object management table 41, the session object storage area 42, and the identifier counter 43 is exclusively controlled by the lock 14.
[0029]
The communication control means 5 controls communication with the terminals 2A to 2C, determines a connection request, a disconnection request, and a message from the terminals 2A to 2C, and determines a terminal connection processing means 6, a terminal disconnection processing means 8, a business processing means, respectively. 7 and a function of distributing a session identifier to the terminals 2A to 2C according to an instruction from the connection processing means 6 or the business processing means 7.
[0030]
The recording medium K1 is a disk, a semiconductor memory, or another recording medium. The program recorded on the recording medium K1 is read by the host computer 1, and by controlling the operation thereof, the communication control unit 5, the terminal connection processing unit 6, the business processing unit 7, the terminal A disconnection processing unit 8, a session identifier generation unit 10, a session object generation unit 11, a session object search unit 12, a session object deletion unit 13, a session object management table 41, a session object management area 42, and an identifier counter 43 are realized.
[0031]
Description of operation of the embodiment
Next, the operation of this embodiment will be described in detail with reference to the drawings.
[0032]
When a connection request from the terminal (for example, the terminal 2B) to the host computer 1 occurs, the communication control means 5 recognizes the connection request and notifies the terminal connection processing means 6 of the connection request (FIG. 7, step S71). , S72). The terminal connection processing means 6 having received the connection request requests the session object generation means 11 to generate a session object.
[0033]
The session object generating means 11 performs the processing shown in the flowchart of FIG. 2 in response to the request.
[0034]
First, the lock 14 is acquired for exclusive control (step S201). Thereafter, a free entry is searched from the session object management table 41 (step S202).
[0035]
If there is no empty entry, it is determined that the session object generation has failed, the lock 14 is released, and the operation ends (NO in step S203, S210, S209).
[0036]
On the other hand, if there is an empty entry, a new session object (for example, session object 421B) is generated and stored in the session object storage area 42 (YES in step S203, S204, S205). Thereafter, a pointer to the session object 421B is stored in the empty entry searched in step S202 (step S206). Further, the session object generation unit 11 passes the entry number of the entry searched in step S202 to the session identifier generation unit 10 and requests generation of a session identifier (step S207).
[0037]
In response to this session identifier generation request, the session identifier generation means 10 increments the identifier counter 43 as shown in the flowchart of FIG. 6 (step S61), and the value of the incremented identifier counter 43 and the input value are inputted. A session identifier as shown in FIG. 5 is generated by combining the entry identifier with the entry number, and the generated session identifier (for example, session identifier B) is returned to the session object generating means 11 (step S62).
[0038]
The session object generating means 11 adds the session identifier B returned from the session identifier generating means 10 to the session object 421B in the session object storage area 42, then releases the lock 14 and ends the operation (FIG. 2). , Steps S208, S209).
[0039]
The terminal connection processing means 6 can judge the operation result (success / failure) of the session object generation means 11, and if the generation is successful, the terminal connection is determined to be successful and the session identifier B is transmitted to the terminal 2B through the communication control means 5. Distribute to On the other hand, in the case of the generation failure, the terminal connection is determined to be unsuccessful, and the connection rejection is notified to the terminal 2B through the communication control means 5.
[0040]
Upon receiving the session identifier B from the host computer 1, the terminal 2B stores the session identifier B in a session identifier storage unit (not shown). Thereafter, when a message requesting the host computer 1 to perform business processing occurs in the terminal 2B, the terminal 2B adds the session identifier B stored in the session identifier storage unit to the message and transmits the message to the host computer 1.
[0041]
When the message with the session identifier B added is sent from the terminal 2B, the communication control means 5 in the host computer 1 recognizes the message and notifies the business processing means 7 (FIG. 7, steps S71, S73). ).
[0042]
The business processing unit 7 extracts the session identifier B added to the message and requests the session object searching unit 12 to search. At that time, the session identifier B is passed as an input.
[0043]
In response to this request, the session object search means 12 performs the processing shown in the flowchart of FIG.
[0044]
First, the lock 14 is acquired (step S31). After that, “entry number” is extracted from the input session identifier B, and array access is made to the session object management table 41 using this “entry number” (step S32). The time required for the search for the array access is extremely short, and a pointer (session object pointer) to the corresponding session object 421B can be obtained instantaneously.
[0045]
If the session object pointer is not stored in the corresponding entry of the session object management table 41, it is determined that the session object search has failed, the lock 14 is released, and the process ends (NO in step S33, S40, S39). This means that the session object has already been destroyed.
[0046]
On the other hand, when the session object pointer is stored in the corresponding entry of the session object management table 41, the value of the session identifier in the session object 421B indicated by the session object pointer and the input session The value is compared with the value of the identifier B (step S34).
[0047]
If the session identifiers do not match, it is determined that the session object search has failed, the lock 14 is released, and the process ends (NO in step S34, S40, S39). This means that the session object has already been deleted, and the corresponding entry has been reused by connecting a new terminal.
[0048]
On the other hand, if the session identifiers match, it is determined that the session object search has succeeded, and a request is made to the session identifier generating means 10 to generate a new session identifier (steps S35 and S36). At this time, the session object search means 12 passes the “entry number” obtained in step S32 to the session identifier generation means 10 and requests generation of a new session identifier.
[0049]
In response to the session identifier generation request, the session identifier generation unit 10 generates a new session identifier B1 including the incremented count value of the identifier counter 43 and the input entry number, and 12 (FIG. 6, steps S61, S62).
[0050]
When the new session identifier B1 is returned from the session identifier generating means 10, the session object searching means 12 updates the session identifier B in the session object 421B to the new session identifier B1, as shown in the flowchart of FIG. Then, the updated session object 421B is returned to the business processing unit 7 (steps S37 and S38). After that, the session object search means 12 releases the lock 14 and ends the processing (Step S39).
[0051]
The session object 421B returned by the session object search unit 12 stores information about the terminal, and the business processing unit 7 can perform a business conscious of the session. That is, continuous communication between the terminal and the host computer can be realized. Further, when returning the message indicating the processing result of the business process requested by the message from the terminal to the terminal 2B, the business processing unit 7 adds a new session identifier B1 and returns the message.
[0052]
When receiving the message to which the new session identifier B1 has been added, the terminal 2B replaces the session identifier B stored in the session identifier storage unit with the new session identifier B1. Thereafter, when a message to be transmitted to the host computer 1 occurs in the terminal 2B, the terminal 2B adds a new session identifier B1 stored in the session identifier storage unit to the message and transmits the message to the host computer 1. When receiving the message with the new session identifier B1 added thereto, the host computer 1 again performs the same processing as the above-described processing, and transmits a message indicating the business processing result to the terminal 2B. The identifier B2 is added to the message and transmitted. The terminal 2B and the host computer 1 repeat the above-described processing until a disconnection request occurs in the terminal 2B. As described above, in the present embodiment, the session identifier is changed even during the session connection, so that the prediction of the session identifier can be made extremely difficult, and as a result, the risk of unauthorized access is extremely reduced. Can be reduced.
[0053]
When a disconnection request occurs in the terminal 2B, the terminal 2B transmits a disconnection request including the latest session identifier (for example, the session identifier Bn) to the host computer 1. Upon receiving the disconnection request, the communication control means 5 in the host computer 1 notifies the terminal disconnection processing means 8 of the request (FIG. 7, steps S71, S74). As a result, the terminal disconnection processing unit 8 passes the session identifier Bn included in the disconnection request to the session object deletion unit 13 and requests that the corresponding session object 421B be deleted.
[0054]
In response to this request, the session object disappearing means 13 performs the processing shown in the flowchart of FIG.
[0055]
First, the session object disappearing means 13 acquires the lock 14 (step S41). After that, the session object annihilation unit 13 extracts the entry number from the session identifier Bn, and accesses the session object management table 41 using the entry number (step S42).
[0056]
If the session object pointer is not stored in the corresponding entry in the session object management table 41, it is determined that the session object has been deleted, the lock 14 is immediately released, and the process ends (NO in step S43). S48, S47).
[0057]
On the other hand, when the session object pointer is stored in the corresponding entry of the session object management table 41, the value of the session identifier in the session object 421B indicated by the session object pointer and the input session The value is compared with the value of the identifier Bn (step S44).
[0058]
If the session identifiers do not match, the operation is terminated after releasing the lock 14 (NO in step S44, S48, S47). This means that the session object has already been deleted and that the entry has been reused by the connection of a new terminal.
[0059]
On the other hand, if the session identifiers match, the corresponding session object 421B is deleted, and the corresponding entry in the session object management table 41 is updated to an empty entry (steps S45 and S46). Thereafter, the lock 14 is released (step S47), and the process ends.
[0060]
Another Embodiment of the Invention
Next, another embodiment of the present invention will be described.
[0061]
FIG. 8 is a block diagram of another embodiment of the present invention, which is different from the embodiment shown in FIG. 1 in that a host computer 1a is provided instead of the host computer 1. The host computer 1a includes a time acquisition unit 9 instead of the identifier counter 43, a session identifier generation unit 10a instead of the session identifier generation unit 10, and a non-communication terminal deletion unit 15 is added. This is different from the host computer 1 shown in FIG. 1 in that a recording medium K2 is provided instead of the recording medium K1.
[0062]
The time obtaining means 9 has a function of obtaining the current time in response to a request from the session identifier generating means 10a and returning the current time to the session identifier generating means 10a.
[0063]
When requested to generate a session identifier from the session object generating means 11 or the session object searching means 12, the session identifier generating means 10a converts the session identifier composed of the entry number and the message reception time as shown in FIG. It has a function to generate and return to the requester. Illustrated as an example is a session identifier of entry number = 2, message reception time = “2002.01.01 01:02:03”.
[0064]
The non-communication terminal deletion unit 15 has a function of deleting, from among the session objects stored in the session object storage area 42, a session object corresponding to a terminal in a non-communication state for a predetermined time or more.
[0065]
The recording medium K2 is a disk, a semiconductor memory, or another recording medium. The program recorded on the recording medium K2 is read by the host computer 1a and by controlling its operation, the communication control means 5, the terminal connection processing means 6, the business processing means 7, the terminal Disconnection processing means 8, time acquisition means 9, session identifier generation means 10a, session object generation means 11, session object search means 12, session object deletion means 13, non-communication terminal deletion means 15, session object management table 41, session object management The area 42 is realized.
[0066]
[Description of Operation of Another Embodiment]
Next, the operation of this embodiment will be described. In the present embodiment, only the operations of the session identifier generating means 10a and the non-communication terminal deleting means 15 are different from the operations of the embodiment of FIG. I will explain only.
[0067]
When the session identifier generation unit 10a receives the entry number from the session object generation unit 11 or the session object search unit 12, and is requested to generate a session identifier (step S207 in FIG. 2 or step S36 in FIG. 3), the session identifier generation unit 10a returns to FIG. As shown in the flowchart of FIG. 5, the time acquisition unit 9 is requested to acquire the current time (step S101). In response to this request, the time obtaining means 9 obtains the current time and returns it to the session identifier generating means 10a. When the current time is returned, the session identifier generating means 10a generates a session identifier composed of the input entry number and the returned current time (message receiving time), and sends the session identifier to the request source (session object generating means 11). Alternatively, it returns to the session object search means 12) (step S102).
[0068]
The non-communication terminal deletion unit 15 performs the process shown in the flowchart of FIG.
[0069]
In step S111, it is determined whether or not there is an unattentioned session object in the session object storage area 42. If there is an unfocused session object, one of them is focused on (YES in step S111, S112). Thereafter, based on the difference between the message reception time and the current time, which are components of the session identifier in the session object of interest, the terminal corresponding to the session object of interest is in a non-communication state for a predetermined time T or longer. It is determined whether or not (step S113). Then, when it is determined that the communication state has not been established for the predetermined time T or more (step S113: YES), the session object of interest is deleted (step S114). The above processing is repeated until there is no session object that has not been noted. A session object corresponding to a terminal that has been in a non-communication state for a long time is likely to be a meaningless object for communication management, such as omission of a disconnection notification or a terminal stall, and deleting it has a significant meaning from the viewpoint of effective use of resources. There is.
[0070]
【The invention's effect】
As described above, the present invention changes the session identifier for uniquely identifying a session object even during a session connection, so that it is extremely difficult to predict the session identifier. Can be. As a result, the risk of unauthorized access impersonating another terminal can be extremely reduced.
[0071]
In addition, since there is provided a non-communication terminal deletion unit for deleting a session object corresponding to a terminal in a non-communication state for a predetermined time or more from the storage area, the memory resources of the host computer can be effectively used.
[Brief description of the drawings]
FIG. 1 is a block diagram of one embodiment of the present invention.
FIG. 2 is a flowchart showing a processing example of a session object generating means 11;
FIG. 3 is a flowchart showing a processing example of a session object search means 12;
FIG. 4 is a flowchart showing a processing example of a session object disappearing means 13;
FIG. 5 is a diagram illustrating a configuration example of a session identifier.
FIG. 6 is a flowchart showing a processing example of a session identifier generating means 10;
FIG. 7 is a flowchart showing a processing example of the communication control means 5;
FIG. 8 is a block diagram of another embodiment of the present invention.
FIG. 9 is a diagram illustrating a configuration example of a session identifier according to another embodiment.
FIG. 10 is a flowchart showing a processing example of a session identifier generating means 10a.
FIG. 11 is a flowchart showing a processing example of a non-communication terminal deletion unit 15;
[Explanation of symbols]
1, 1a ... host computer
2A ~ 2C ... terminal
3. Network
4 ... Memory
41: Session object management table
42: Session object storage area
421A, 421B ... session object
43 ... Identifier counter
5. Communication control means
6. Terminal connection processing means
7 Business processing means
8. Terminal disconnection processing means
9: Time acquisition means
10, 10a ... session identifier generating means
11 Session object generating means
12. Session object search means
13: Session object disappearance means
14 ... Lock
15 ... wireless communication terminal deletion means
K1, K2 ... recording medium

Claims (8)

For each terminal in the session connection state, a session object that manages information about the terminal is managed using a session identifier that uniquely identifies the session object, and a message with a session identifier added is sent from the terminal. In the case, a session identifier management device in a host computer that searches for a session object specified by a session identifier added to the message,
A session identifier management device, comprising: means for changing a session identifier for specifying a session object of the terminal when the terminal is in a session connection state, and transmitting the changed session identifier to the terminal. The session identifier management device according to claim 1,
A session identifier management apparatus, characterized in that said means has a configuration in which, when a message is sent from said terminal, a session identifier for specifying a session object of said terminal is changed. A session identifier management device in a host computer that establishes a session with a terminal and performs communication,
At the time of a connection request from a terminal, a session object for managing information on the terminal is generated and a session identifier generation request is output, and a session identifier returned in response to the session identifier generation request is added to the session object. Session object generating means for storing in a storage area and transmitting to the terminal;
When a message to which a session identifier is added is sent from the terminal, a session object specified by the added session identifier is searched from the storage area, and a session identifier generation request is output. A session identifier in the session object specified by the current session identifier, to a session identifier returned in response to the session identifier generation request, and further, transmitting the returned session identifier to the terminal. Means,
A session identifier management apparatus comprising: a session identifier generation unit that generates a new session identifier in response to a session identifier generation request, and returns the generated session identifier to a request source. The session identifier management device according to claim 3,
An identifier counter, and
A session identifier management unit configured to increment the identifier counter in response to a session identifier generation request and to generate a session identifier including the count value of the identifier counter after the increment. . The session identifier management device according to claim 3,
A session identifier management apparatus, wherein the session identifier generation means generates a session identifier including a current time in response to a session identifier generation request. The session identifier management device according to claim 5,
Wireless terminal deletion means for deleting a session object of a terminal in a non-communication state for a predetermined time or more based on a session identifier added to each session object stored in the storage area. Session identifier management device. For each terminal in the session connection state, a session object that manages information about the terminal is managed using a session identifier that uniquely identifies the session object, and a message with a session identifier added is sent from the terminal. In the case, a session identifier management method in a host computer that searches for a session object specified by a session identifier added to the message,
When a terminal is in a session connection state, a session identifier that specifies a session object of the terminal is changed, and the changed session identifier is transmitted to the terminal. For each terminal in the session connection state, a session object that manages information about the terminal is managed using a session identifier that uniquely identifies the session object, and a message with a session identifier added is sent from the terminal. In this case, a host computer that searches for a session object specified by the session identifier added to the message is
A program for causing a terminal to change a session identifier that identifies a session object of the terminal when the terminal is in a session connection state, and to function as means for transmitting the changed session identifier to the terminal.

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