JP2004252877A - Communication system, server device, and socket communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent illicit access based on a specific port number to a computer. <P>SOLUTION: Key data are extracted by a server 1 to be transmitted to a client 2. In the server 1 and the client 2, a TCP port number matching the key data is extracted and defined as a TCP port number, which is used for socket communication, with respect to application. On the basis of the TCP port number, socket communication is carried out between the server 1 and the client 2. In every lapse of a fixed time, a different TCP port number is extracted to be defined to the application. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a communication system, a server device, and a socket communication method using, for example, a TCP port number.
[0002]
[Prior art]
FIG. 7 is a diagram showing an outline of socket communication by a conventional communication system.
In the case of performing socket communication between a plurality of, for example, two computers 4 and 5, a common application program corresponding to the socket communication is installed in each of the computers 4 and 5, and these application programs are assigned in advance. A port number for socket communication, for example, a TCP port number "A" is defined in an application program, and socket communication is performed between the computers 4 and 5 (for example, see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP-A-11-175439
[0004]
[Patent Document 2]
JP-A-7-21724
[0005]
[Problems to be solved by the invention]
However, if the set TCP port number “A” is known by others, there is a risk that the computers 4 and 5 may be subject to unauthorized access. Since the defined TCP port number “A” is fixed, once the TCP port number “A” is known, the computers 4 and 5 are always subject to unauthorized access.
[0006]
The present invention has been made in view of the above problems, and has as its object to provide a communication system, a server device, and a socket communication method that can prevent unauthorized access to a computer based on a specific port number. .
[0007]
[Means for Solving the Problems]
That is, a communication system according to claim 1 of the present invention is a communication system including a first computer and a second computer, wherein the first computer corresponds to port number information for socket communication. Key data setting means for setting key data to be set, key data resetting means for resetting the key data set by the key data setting means to the key data setting means, and the key data according to the key data resetting means. Key data transmitting means for transmitting the new key data set by the setting means to the second computer; and the second computer based on the key data set by the key data setting means in accordance with the key data resetting means Port number information setting means for setting port number information common to Port number information storage means for storing the port number information set by the port number information setting means, and port number information common to the port number information based on the port number information stored by the port number information storage means. Communication means for communicating with the second computer, the second computer comprising: key data reception means for receiving key data transmitted by the first computer; and a key received by the key data reception means. Port number information setting means for setting port number information common to the first computer based on data; port number information storage means for storing new port number information set by the port number information setting means; Based on the port number information stored by the port number information storage means, this port Wherein the common port number information and issue information and a communication means for communicating with said stored first computer.
[0008]
That is, in the communication system according to claim 1 of the present invention, when the key data set in the first computer is reset by the key data resetting means, the key data is transmitted to the second computer by the key data transmitting means. When the key data is transmitted and received, the port number information setting means sets the common port number information with the first computer, and the first computer sets the common port number information with the port number information setting means. I do. Then, the set port number information is stored in the port number information storage means of the first and second computers, and based on the port number information, socket communication between the first computer and the second computer is performed by the communication means. Will be executed.
[0009]
The communication system according to claim 2 of the present invention is the communication system according to claim 1, wherein the first computer further includes a counting unit, and the key data resetting unit includes the counting unit. The key data set by the key data setting means is reset every time a predetermined time is counted.
[0010]
That is, in the communication system according to claim 2 of the present invention, the key data is reset by the key data resetting unit every time the predetermined time is counted by the counting unit of the first computer. Then, the reset key data is transmitted to the second computer by the key data transmitting means, and when the key data is received, the port number information setting means sets the common port number information with the first computer, Common port number information is set by the port number information setting means of one computer. Then, the set port number information is stored in the port number information storage means of the first and second computers, and based on the port number information, socket communication between the first computer and the second computer is performed by the communication means. Will be executed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an outline of a communication system according to an embodiment of the present invention.
When performing socket communication between a plurality of computers, for example, a synchronization server 1 (hereinafter, referred to as a server 1) and a synchronization client 2 (hereinafter, referred to as a client 2), first, a common application program corresponding to the socket communication (Hereinafter, referred to as an application) are installed in the server 1 and the client 2, respectively. It is necessary to associate a TCP port number for socket communication with an application. The TCP port number associated with the application installed on the server 1 and the TCP port number associated with the application installed on the client 2 must be common.
[0012]
Therefore, a common socket communication port number corresponding to the application is stored in a communication information management table (not shown) provided in the server 1 and the client 2, for example. This communication information management table manages a TCP port number used by the application for socket communication. Hereinafter, the process of storing the TCP port number corresponding to the application in the communication information management table is referred to as the process of defining the TCP port number for the application. Thus, socket communication using an application is performed between the server 1 and the client 2.
When a plurality of types of applications are installed in the server 1 and the client 2, a TCP port number is defined for each type of application.
[0013]
In the present embodiment, the TCP port number defined for the application of the server 1 and the client 2 is automatically changed to a different TCP port number, for example, “B” after synchronization between the server 1 and the client 2. change. Then, the TCP port number is automatically changed to, for example, "C" or "D" every time a predetermined time elapses. As a result, even if a specific TCP port number is known to another person, continuous unauthorized access to the server 1 and the client 2 cannot be executed.
[0014]
FIG. 2 is a block diagram showing the configuration of the communication system according to the embodiment.
The communication system shown in FIG. 2 is configured by connecting a server 1 and a client 2 via a communication cable 3. The communication cable 3 is, for example, an Ethernet (registered trademark) cable.
[0015]
The server 1 extracts at least one from a key data group in which key data associated with a TCP port number is stored in advance, and defines a TCP port number corresponding to the extracted key data to an application. And it has a function of executing socket communication with the client 2 based on this TCP port number. It also has a function of extracting and defining a different TCP port number every time a predetermined time elapses.
[0016]
The client 2 has a function of defining a TCP port number common to the TCP port number extracted by the server 1 for an application and executing socket communication with the server 1.
[0017]
As shown in FIG. 2, the server 1 is configured by connecting a storage unit 12 and a communication interface 13 to a CPU 11. The communication interface 13 is connected to the communication cable 3.
[0018]
The CPU 11 executes a TCP port number change process. In this TCP port number change process, at least one type of key data is randomly extracted from the key data stored in the key data storage area 12a of the storage unit 12 in the server 1 and transmitted to the client 2, and a new TCP port number is set. The process of extracting and defining the application to the application, the process of extracting the TCP port number based on the extracted key data, and using the extracted TCP port number as a new TCP port number used for socket communication with the client 2 to the application. This is the process of defining.
[0019]
The storage unit 12 is a memory in which information stored therein can be rewritten.
The storage unit 12 has a key data storage area 12a for storing key data, and a key data / TCP port number conversion table storage area for storing a key data / TCP port number conversion table in which key data is associated with a TCP port number. 12b, a buffer memory 12c for temporarily storing working data, and a TCP port number storage area 12d for storing a TCP port number extracted by the TCP port number changing process. Further, an area (not shown) for storing an application for socket communication is provided. A plurality of types of applications can be stored in the application storage area.
[0020]
FIG. 3 shows the contents of the key data stored in the key data storage area 12a shown in FIG.
As shown in FIG. 3, the key data storage area 12a stores key data composed of a plurality of characters, for example, six alphabets. The number of key data is the same as the number of TCP port numbers that can be defined for the application.
[0021]
Further, among the TCP port numbers corresponding to the key data, there are numbers already used by the applications installed in the server 1 and the client 2. These TCP port numbers must not be specified as the destination TCP port numbers. Therefore, a prohibition flag “1” is set to key data corresponding to a TCP port number already used, and a prohibition flag “0” is set to other key data. Key data for which the prohibition flag “1” is set is not extracted as key data corresponding to the change destination TCP port number.
[0022]
FIG. 4 is a diagram showing the contents of the key data / TCP port number conversion table stored in the key data / TCP port number conversion table storage area 12b shown in FIG.
In the key data / TCP port number conversion table, key data is stored in association with a predetermined range, for example, 256 types of TCP port numbers from 0 to 255, as shown in FIG.
[0023]
The TCP port number storage area 12d stores the TCP port number currently used for the socket communication between the server 1 and the client 2, and the TCP port number extracted in the TCP port number change process.
[0024]
The communication interface 13 is for connecting the client 2 with the communication cable 3, and transmits a control signal and various data input by the CPU 11 to the client 2. Further, it receives the control signals and various data transmitted from the client 2 and outputs them to the CPU 11.
[0025]
As shown in FIG. 2, the client 2 is configured by connecting a storage unit 22 and a communication interface 23 to a CPU 21. The communication interface 23 is connected to the communication cable 3.
[0026]
The CPU 21 executes a control process for changing the TCP port number. That is, a process of receiving the key data transmitted by the server 1, a process of extracting the TCP port number based on the received key data, and a process of defining the extracted TCP port number for the application are executed.
[0027]
The storage unit 22, like the storage unit 12, is a memory in which information stored therein can be rewritten.
The storage unit 22 includes a key data / TCP port number conversion table 22a that stores key data and TCP port numbers in association with each other, a TCP port number storage area 22b, and a buffer memory 22c that temporarily stores working data. Provided. Further, an area for storing an application common to the server 1 is provided.
[0028]
In the key data / TCP port number conversion table storage area 22a, the same key data / TCP port number conversion table (see FIG. 4) as the contents stored in the key data / TCP port number conversion table storage area 12b of the server 1 is stored. It is memorized.
[0029]
Like the TCP port number storage area 12d of the server 1, the TCP port number storage area 22b stores the TCP port number used for the socket communication between the server 1 and the client 2 and the change destination extracted in the TCP port number change processing. Is stored.
[0030]
The communication interface 23 is for connecting the server 1 with the communication cable 3 and transmits control signals and various data input by the CPU 21 to the server 1. Further, it receives the control signals and various data transmitted from the server 1 and outputs them to the CPU 21.
[0031]
Next, the TCP port number automatic change processing of the communication system having the above configuration will be described.
FIG. 5 is a diagram showing an outline of a TCP port number automatic change process of the communication system according to the embodiment.
The server 1 performs socket communication with the client 2 based on the old TCP port number, that is, the TCP port number before the change.
The server 1 extracts the same number of key data as the number of TCP port numbers to be changed, that is, the number of TCP port numbers used for socket communication with the client 2 from the key data corresponding to the 256 types of TCP port numbers ( Step S1). Next, the extracted key data is transmitted to the client 2. When receiving the key data, the client 2 transmits a reception confirmation signal indicating that the key data has been received to the server 1 (step S12). When receiving the reception confirmation signal, the server 1 reads the key data / TCP port number conversion table (step S4) and extracts the TCP port number corresponding to the key data (step S5).
[0032]
On the other hand, when the client 2 transmits the key data reception confirmation signal to the server 1, the client 2 reads the key data / TCP port number conversion table (step S14) and extracts the TCP port number corresponding to the key data in the same manner as the server 1. (Step S15). As a result, a TCP port number common to the server 1 and the client 2 is generated.
[0033]
Then, the socket connection between the server 1 and the client 2 is executed based on the new TCP port number, that is, the newly generated TCP port number. The socket connection is a process for securing a line used for the socket communication before the socket communication between the server 1 and the client 2.
[0034]
Next, the server 1 executes a process of changing assignment to a task (step S8). In this allocation change processing, the newly generated TCP port number is stored in the TCP port number storage areas 12d and 22b, and is defined as a new TCP port number used by the application installed in the server 1 and the client 2. Processing. The assignment change process is also executed by the client 2 (step S18). For this allocation process, a conventionally applied procedure can be used, and the type is not limited.
[0035]
Then, socket disconnection between the server 1 and the client 2 based on the old TCP port number is executed. This socket disconnection is a process of disconnecting a line established for socket communication between the server 1 and the client 2.
[0036]
When the server 1 counts a predetermined time, it extracts the key data again, and thereafter repeats the processing shown in FIG. 5 (step S11). As a result, the TCP port number commonly defined for the applications installed on the server 1 and the client 2 is changed every predetermined time.
[0037]
Next, the details of the TCP port number automatic change processing of the communication system according to the above configuration will be described.
FIG. 6 is a flowchart showing a TCP port number automatic change process of the communication system.
First, the socket communication is performed between the server 1 and the client 2 based on one or more of the 256 types of TCP port numbers from 0 to 255, for example.
In the TCP port number storage area 12d, TCP port numbers currently used for socket communication, for example, "2" and "255" are stored.
[0038]
First, the CPU 11 of the server 1 accesses the TCP port number storage area 12d and checks the number of currently used TCP port numbers. Then, key data of the same number as the number of TCP port numbers stored in the TCP port number storage area 12d is extracted from the 256 types of key data stored in the key data storage area 12a (step S1). However, key data associated with the prohibition flag “1”, for example, “NHCZSP” and “ZAUCVL” are key data corresponding to TCP port numbers “2” and “255” already used for socket communication. So do not extract. The key data to be extracted are, for example, “GGDRME” and “ASOIGY”.
[0039]
The method of extracting key data from the key data storage area 12a is not limited to the method described here, but may be a method of extracting key data different from the key data corresponding to the TCP port number currently used for socket communication. If there is, the type does not matter.
[0040]
Then, the extracted key data “GGDRME” and “ASOIGY” are transmitted to the client 2 via the communication interface 13 and the connection cable 3 (step S2).
[0041]
The processing related to the transmission of the key data may be executed based on, for example, an IP address separately stored in the storage unit 12 of the server 1 and the storage unit 22 of the client 2, or may be executed based on another communication protocol. No problem.
[0042]
When the CPU 21 of the client 2 receives the key data “GGDRME” and “ASOIGY” transmitted from the server 1 via the communication interface 23, the key data reception confirmation signal for notifying the server 1 that the key data has been received. Is transmitted to the server 1 (steps S12 and S13).
[0043]
When receiving the key data reception confirmation signal via the communication interface 13, the CPU 11 of the server 1 reads the key data / TCP port number conversion table stored in the key data / TCP port number conversion table storage area 12 b of the storage unit 12. (Steps S3 and S4). In the key data / TCP port number conversion table, the received key data "GGDRME" and "ASOIGY" are searched, and TCP port numbers "100" and "254" associated with these key data are extracted (step). S5). As a result, a new TCP port number used for the socket communication between the server 1 and the client 2 is generated.
[0044]
On the other hand, when the client 2 transmits the key data reception confirmation signal to the server 1 in step S13, the client 2 reads the key data / TCP port number conversion table from the key data / TCP port number conversion table storage area 22a as in the server 1, and The TCP port numbers “100” and “254” corresponding to the key data “GGDRME” and “ASOIGY” are extracted (steps S14, S15). As a result, a new and common TCP port number is generated for the server 1 and the client 2.
[0045]
The CPU 11 of the server 1 stores the new TCP port numbers “100” and “254” extracted in step S5 in the TCP port number storage area 12d (step S6).
[0046]
Further, the CPU 21 of the client 2 stores the new TCP port numbers “100” and “254” extracted in step S15 in the TCP port number storage area 22b (step S16).
[0047]
The new TCP port numbers “100” and “254” stored in step S6 and step S16 correspond to the old TCP port numbers “2” and “255” already stored in the TCP port number storage area 12d and the TCP port number storage area 22b. ", For example, by a flag.
[0048]
Then, a socket connection is performed between the server 1 and the client 2 based on the TCP port numbers "100" and "254" stored in the TCP port number storage areas 12d and 22b, respectively (steps S7 and S17). This socket connection is performed regardless of the TCP port number currently defined for the application.
[0049]
Then, the CPU 11 executes a process of changing assignment of the application installed in the storage unit 12 to a task. That is, instead of the old TCP port number, the new TCP port numbers “100” and “254” stored in the TCP port number storage area 12d are defined to the application as TCP port numbers used for socket communication (step S8). This assignment change process is also executed by the CPU 21 of the client 2. That is, for the application installed in the storage unit 22, the TCP port numbers “100” and “254” stored in the TCP port number storage area 22b are defined instead of the old TCP port number (Step S18).
Then, the socket is disconnected between the server 1 and the client 2 using the old TCP port numbers “2” and “255” (steps S9 and S19).
[0050]
Then, the server 1 deletes the old TCP port numbers “2” and “255” from the TCP port numbers stored in the TCP port number storage area 12d (Step S10). The client 2 deletes the old TCP port numbers “2” and “255” from the TCP port numbers stored in the TCP port number storage area 22b (Step S20).
[0051]
Accordingly, the CPU 11 of the server 1 executes a process related to rewriting the prohibition flag corresponding to the key data stored in the key data storage area 12a. That is, the prohibition flag “1” is set for key data corresponding to the new TCP port number defined in the allocation change processing, and the prohibition flag “0” is set for other key data.
[0052]
Note that the procedures related to the processing up to TCP port number extraction, socket connection, socket disconnection, and TCP port number definition processing are not limited to the above-described procedures, and the use of the old TCP port number for socket communication is stopped. The type does not matter as long as the procedure uses the new TCP port number extracted in steps S5 and S15 for a new socket communication.
[0053]
Then, when the CPU 11 of the server 1 counts a predetermined time (step S11), the processing after step S1 is executed again. Thus, different TCP port numbers can be periodically generated and defined for the application.
[0054]
Therefore, according to the communication system having the above configuration, when key data is extracted by the server 1, the key data is transmitted to the client 2. Next, in the server 1 and the client 2, a TCP port number corresponding to the key data is extracted, and socket communication between the server 1 and the client 2 is executed. Since a TCP port number is newly extracted every time a predetermined time elapses, it is possible to prevent another person from continuously performing unauthorized access to the server 1 and the client 2 based on the specific TCP port number. .
[0055]
In the above-described embodiment, the server 1 randomly extracts key data, extracts a TCP port number based on the key data, and the client 2 uses a common key with the server 1 based on the key data received from the server 1. The configuration is such that the TCP port number is extracted. Instead of the key data, a desired number of TCP port numbers are randomly extracted from, for example, 256 types of TCP port numbers stored in the storage unit 12 in the server 1. Then, this TCP port number is transmitted to the client 2 or the client 2 is instructed to set the same TCP port number as the TCP port number set in the server 1, and the client 2 transmits the TCP port number transmitted by the server 1 to the client 2. It may be configured to receive or generate a TCP port number common to the server 1.
[0056]
The present invention is not limited to the above-described embodiment, and can be variously modified in an implementation stage without departing from the gist of the invention. Further, the embodiment includes inventions at various stages, and various inventions can be extracted by appropriate combinations of a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiments, the problem described in “Problems to be Solved by the Invention” can be solved, and the problem described in the “Effect of the Invention” section can be solved. In the case where a certain effect can be obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.
[0057]
【The invention's effect】
As described above, according to the communication system of the first aspect of the present invention, when the key data set in the first computer is reset by the key data resetting means, the key data is transmitted by the key data transmitting means. When the key data is transmitted to the second computer and received, the port number information setting means sets port number information common to the first computer, and the port number information setting means of the first computer sets common port number information. Set the port number information. Then, the set port number information is stored in the port number information storage means of the first and second computers, and based on the port number information, socket communication between the first computer and the second computer is performed by the communication means. Is executed, the port number information commonly set for the first and second computers can be changed after the synchronization between the first and second computers.
[0058]
Further, according to the communication system of the second aspect of the present invention, the key data is reset by the key data resetting unit each time the predetermined time is counted by the counting unit of the first computer. Then, the reset key data is transmitted to the second computer by the key data transmitting means, and when the key data is received, the port number information setting means sets the common port number information with the first computer, Common port number information is set by the port number information setting means of one computer. Then, the set port number information is stored in the port number information storage means of the first and second computers, and based on the port number information, socket communication between the first computer and the second computer is performed by the communication means. , The port number information can be changed periodically.
[0059]
Therefore, the present invention can prevent unauthorized access to a computer based on a specific port number.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a communication system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a communication system according to the embodiment.
FIG. 3 is a view showing contents of key data stored in a key data storage area 12a shown in FIG. 2;
FIG. 4 is a diagram showing contents of a key data / TCP port number conversion table stored in a key data / TCP port number conversion table storage area 12b shown in FIG. 2;
FIG. 5 is a view showing an outline of a TCP port number automatic change process of the communication system according to the embodiment.
FIG. 6 is a flowchart showing a TCP port number automatic change process of the communication system.
FIG. 7 is a diagram showing an outline of socket communication by a conventional communication system.
[Explanation of symbols]
1 ... Synchronization server
2. Synchronous client
3. Connection cable
11 CPU
12. Memory unit
12a Key data storage area
12b Key data TCP port number conversion table storage area
12c buffer memory
12d TCP port number storage area
13. Communication interface
21 CPU
22..Storage unit
22a Key data TCP port number conversion table
22b TCP port number storage area
22c buffer memory
23 Communication interface

Claims (8)

In a communication system including a first computer and a second computer,
The first computer comprises:
Key data setting means for setting key data corresponding to port number information for socket communication,
Key data resetting means for resetting the key data set by the key data setting means to the key data setting means;
Key data transmitting means for transmitting new key data set by the key data setting means to the second computer according to the key data resetting means;
Port number information setting means for setting port number information common to the second computer based on key data set by the key data setting means according to the key data resetting means;
Port number information storage means for storing the port number information set by the port number information setting means,
Based on the port number information stored by the port number information storage means, a communication means for communicating with the second computer in which the port number information and the common port number information are stored;
The second computer comprises:
Key data receiving means for receiving key data transmitted by the first computer;
Port number information setting means for setting port number information common to the first computer based on the key data received by the key data receiving means;
Port number information storage means for storing new port number information set by the port number information setting means;
Communication means for communicating with the first computer in which the port number information and the common port number information are stored based on the port number information stored by the port number information storage means. system. The first computer further includes a counting unit,
2. The communication system according to claim 1, wherein the key data resetting means resets the key data set by the key data setting means every time a predetermined time is counted by the counting means. In a communication system including a first computer and a second computer,
The first computer comprises:
Port number information setting means for setting port number information for socket communication;
Port number information resetting means for resetting the port number information set by the port number information setting means to the port number information setting means,
Port number information storage means for storing the port number information set by the port number information setting means according to the port number information resetting means,
Common port number information setting instructing means for instructing the second computer to set common port number information with the port number information set by the port number information setting means according to the port number information resetting means;
Based on the port number information stored by the port number information storage means, comprising communication means for communicating with the second computer in which the port number information and the common port number information are set and stored;
The second computer comprises:
Common port number information setting means for setting port number information common to the first computer in accordance with an instruction from the first computer;
Port number information storage means for storing the port number information set by the common port number information setting means,
Communication means for communicating with the first computer in which port number information common to the port number information is set and stored based on the port number information stored by the port number information storage means. Communication system. The first computer further includes a counting unit,
4. The communication system according to claim 3, wherein said port number information resetting means resets the port number information set by said port number information setting means every time a predetermined time is counted by said counting means. . Key data setting means for setting key data corresponding to port number information for socket communication,
Key data resetting means for resetting the key data set by the key data setting means to the key data setting means;
Key data transmitting means for transmitting new key data set by the key data setting means to another computer according to the key data resetting means;
Port number information setting means for setting port number information common to the other computer based on the key data set by the key data setting means according to the key data resetting means,
Port number information storage means for storing the port number information set by the port number information setting means,
Communication means for communicating with the other computer storing the port number information and the common port number information based on the port number information stored by the port number information storage means. . Furthermore, it has a counting means,
6. The server device according to claim 5, wherein the key data resetting unit resets the key data set by the key data setting unit every time a predetermined time is counted by the counting unit. A socket communication method used in a communication system including a first computer and a second computer,
The first computer comprises:
A key data setting step of setting key data corresponding to port number information for socket communication,
A key data resetting step of resetting the key data set by the key data setting step to the key data setting step;
A key data transmitting step of transmitting new key data set in the key data setting step to the second computer according to the key data resetting step;
A port number information setting step of setting common port number information with the second computer based on the key data set in the key data setting step according to the key data resetting step;
Port number information storage means for storing the port number information set in the port number information setting step;
Based on the port number information stored by the port number information storage means, a communication step of communicating with the second computer in which the port number information and the common port number information are stored,
The second computer comprises:
A key data receiving step of receiving key data transmitted by the first computer;
A port number information setting step of setting port number information common to the first computer based on the key data received in the key data receiving step;
Port number information storage means for storing new port number information set in the port number information setting step;
A communication step for communicating with the first computer in which the port number information and the common port number information are stored based on the port number information stored by the port number information storage means. Communication method. The first computer further includes a counting step,
8. The socket communication method according to claim 7, wherein in the key data resetting step, the key data set in the key data setting step is reset every time a predetermined time is counted in the counting step.

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