JPH10224507A - Data communication system and data communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten connection time to be the object of charging in data communication. SOLUTION: When calling is performed from a terminal side A (S1), a center side B is informed of ring signals RING and a calling number CALLING ID. A CPU refers to the calling number CALLING ID and accesses a hard disk while maintaining the on-hook state of a portable telephone set (S2), reads a password and a mail file, transfers them to a RAM and prepares for the authentication of the password and the transfer of the mail file (S3). Thereafter, the portable telephone set is controlled so as to be changed from the on-hook state to an off-hook state and a communication channel is connected with the terminal side A. Then, when response signals are detected in the portable information communication terminal of the terminal side A, the portable information communication terminal transfers the password to the center side B (S5). On the center side B, the authentication processing of the password is performed (S6). In this case, when the password matches, the CPU reads the mail file stored in the RAM and transfers it to the terminal side A (S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system and a data communication method using calling number notification, and more particularly to a data communication system and a data communication method suitable for personal computer communication.

[0002]

2. Description of the Related Art With the progress of the information society, there is an increasing demand for accessing necessary information regardless of time and place. Portable information communication terminal (PDA: personal digital)
assistannt) is a communication terminal developed to meet such demands. By using this portable information communication terminal connected to a portable telephone, a user can access information stored in a server which is far away, regardless of time and place.

[0003] For example, when the above-described system is applied to personal computer communication, when a user accesses a server using a portable information communication terminal, the user downloads an electronic mail stored therein, or You can upload an email to the other party. Thus, for example, a sales person can place an order for a product at the customer's site, and information can be quickly transmitted.

[0004]

In such data communication, first, when a portable telephone of the portable information communication terminal is placed in an off-hook state and a call is made, the server detects a ring signal, and the portable telephone communicates with the portable telephone. Is changed from the on-hook state to the off-hook state to establish communication. Billing starts when the server goes off-hook. After this,
The server requests transmission of the user ID and the password. When the user ID and the password are transmitted from the portable information communication terminal to the server in response, the server performs an authentication process using the password.

In this case, the server searches the storage area of the hard disk in which the password is stored based on the user ID, and compares the previously registered password with the received password to perform an authentication process. Then, only when the user is authenticated as a valid user, the portable information communication terminal can access a predetermined file. Thereafter, when an instruction to download a file is issued from the portable information communication terminal, the server searches the storage area of the hard disk in which the file is stored, and transfers this to the portable information communication terminal.

In such a data communication system, communication is not performed during a password search period and a file search period, but these searches must be performed during a charging period, so that communication fees are high. Will be. In addition, the charge for the mobile phone service is higher than the charge for the normal telephone line service, and charging for 12 seconds per 10 yen has been a serious problem.

[0007] The present invention has been made in view of the above circumstances, and has as its object to realize inexpensive data communication by shortening the communication time to be charged.

[0008]

According to the first aspect of the present invention, there is provided a data communication system for performing data communication via a communication network which is charged when an off-hook state is established. A terminal for notifying a calling number when making a call, storage means for storing data in association with the calling number, and receiving the calling number from the terminal;
Reading means for referencing the calling number and reading the corresponding data from the storage means in the on-hook state, and switching from the on-hook state to the off-hook state after the reading by the reading means is completed, and reading the read data. A server having data transmission means for transmitting the data to the terminal.

Further, in the invention according to claim 2,
In a data communication system for performing data communication via a communication network in which charging is performed when a terminal goes off-hook between a terminal and a server, the terminal notifies a calling number of the terminal when making a call. Means, storage means for storing a password, when detecting a response signal from the server, read the password from the storage means,
A password notifying unit for notifying the server of the calling number, the server storing a password and data registered in advance in association with the calling number, and when receiving the calling number from the terminal, on-hook. In the state, referring to the calling number, reading out the corresponding password and data from the storage means to prepare for password authentication and data transmission, and after the preparation is completed, the on-hook state is changed to the off-hook state. Switching to a state, responding means for notifying the terminal of the response signal, receiving a password from the terminal, authenticating means for performing an authentication process based on the received password and the prepared password; Data transmission means for transmitting the prepared data to the terminal when the And it said that there were pictures.

[0010] Further, in the invention according to claim 3,
In a data communication system for performing data communication via a communication network in which charging is performed when a terminal goes off-hook between a terminal and a server, the terminal notifies a calling number of the terminal when making a call. Means, storage means for storing a password, when detecting a response signal from the server, read the password from the storage means,
A password notifying unit that notifies the server of the password, the server stores a plurality of passwords and data registered in advance in association with the calling number, and receives the calling number from the terminal. While in the on-hook state, referring to the calling number, reading out a plurality of passwords and data corresponding to the calling number from the storage means to prepare for password authentication and data transmission, and after the preparation is completed, Switching from an on-hook state to an off-hook state, a response unit for notifying the terminal of the response signal, and an authentication unit for performing an authentication process based on the received password and a plurality of prepared passwords when a password is received from the terminal. Preparation for responding to the authenticated password when authenticated by the authentication means Characterized in that the data and a data transmission means for transmitting to said terminal.

Further, according to the invention described in claim 4, in a data communication system for performing data communication via a communication network in which charging is performed when an off-hook state is established between a terminal and a server, the terminal includes: Calling number notification means for notifying the calling number of the terminal when making a call, storage means for storing a password and a sub-ID, and upon detecting a response signal from the server, the password and the sub- Notifying means for reading an ID and notifying the server of the ID, the server storing a plurality of passwords, sub-IDs, and data registered in advance in association with the calling number, When the calling number is received from the terminal, the on-hook state refers to the calling number and a plurality of passwords, sub IDs, and data corresponding to the calling number Preparing means for reading from the storage means and preparing for password authentication and data transmission, after the preparation is completed, switching from an on-hook state to an off-hook state, and responding means for notifying the terminal of the response signal, When receiving the sub-ID and the password from the terminal, based on the prepared password corresponding to the received sub-ID and the received password, an authentication unit for performing an authentication process; and Data transmission means for transmitting prepared data corresponding to the authenticated password to the terminal.

Further, in the invention according to claim 5,
In a data communication method for performing data communication between a terminal and a server via a telephone communication network, when making a call from the terminal to the server, transmitting a calling number of the terminal to the server, Receiving the calling number from the terminal, while in an on-hook state, prepares for authentication of a password corresponding to the calling number and transmission of data corresponding to the calling number, and the server prepares for the authentication and the transmission After the preparation is completed, the state is switched from the on-hook state to the off-hook state, a response signal is transmitted to the terminal, and when the terminal detects the response signal, a password is transmitted to the server. The server performs an authentication process based on the password thus obtained, and the server is authenticated by the authentication process as being valid. The case, and transmits the prepared data to the terminal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

A. First Embodiment 1. First Embodiment Configuration of First Embodiment Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to the drawings. 1-1: Overall System Configuration FIG. 1 is a block diagram of a data communication system according to an embodiment of the present invention. In the figure, a terminal side A and a center side B are connected via a communication network NET so that information can be mutually transmitted. In this example, it is assumed that the terminal side A accesses the center side B and reads out the mail file stored therein.

Reference numeral 10 denotes a portable information communication terminal, which is a keyboard capable of inputting instructions and information by combining characters and symbols, a display section for displaying information, and a memory for storing a password and a script file for communication. And a CPU for controlling the entire terminal. When detecting a response signal from the server described later, the CPU reads the password from the memory and notifies the server of the password.
Reference numeral 11 denotes a data communication adapter, which functions as an interface for communicating data.

Reference numeral 12 denotes a portable telephone, which communicates with a communication network NET including a base station, an exchange, and the like. By the way, many mobile phones have a calling number notification function for notifying the other party of the telephone number of the calling station.
When this function is used, the receiving side is on-hook (before receiving a call)
You can find out the phone number of the calling party with. The mobile phone 12 according to the present embodiment has a calling number notification function, and the calling number notification function is set to an ON state. Therefore, the center side B
Is called, the ring signal RING and the calling number CALLING ID are transferred to the center side B.

Reference numeral 20 denotes a server constituted by a personal computer or the like, in which a mail file is stored for each user. 21 is a data communication adapter functioning as a communication interface;
Is a mobile phone connected to the communication network NET.

1-2: Server Configuration Next, the configuration of the server will be described with reference to FIG. FIG. 2 is a block diagram of the center side mainly including the server according to the present embodiment. In the figure, a CPU 200 controls the entire server 20 and is connected to each component via a bus. A RAM 201 is used as a work area for the CPU 200, and temporarily stores a password and a mail file. Reference numeral 202 denotes a ROM, which stores an operation program of the CPU 200 and the like. Reference numeral 203 denotes a display for displaying a communication state. Reference numeral 204 denotes a hard disk, which stores e-mail uploaded via the data communication adapter 21 for each user ID.

Here, the contents of the hard disk will be described with reference to FIG. As shown in the figure, the storage area of the hard disk is divided for each calling number CALLING ID, and the calling number CALLING ID is used as a tag of the divided storage area. That is, the calling number CALLING ID is used instead of the user ID for identifying the user. In each of the storage areas F1, F2,..., Fn, a password and a mail file registered in the center B in advance are stored.
Therefore, by accessing the hard disk 204 with reference to the calling number CALLING ID, the password and the mail file can be obtained. For example, CALLING ID1 = 03
If it is 0123456, the password abcdef and the mail files M1 to M3 can be obtained by accessing the hard disk 204 with “030123456” as a tag.

The calling number CALLING ID is transmitted from the terminal A to the center B together with the ring signal RING as described above.
The mobile phone 22 can detect this in an on-hook state. Further, since the charging is started only after the off-hook state, the password and the mail file can be prepared before the charging. In this example, the CPU 200 executes the calling number CALLIN
When the G ID is transferred, the password and the mail file are read from the hard disk 204 and transferred to the RAM 201 before going off-hook. Thus, the search for the password and the mail file can be performed before the charging period, so that the data communication can be performed at low cost.

2. Operation of First Embodiment Next, an operation of the first embodiment will be described with reference to the drawings. FIG. 4 is a sequence diagram for explaining the operation of the communication system according to the first embodiment. First, terminal A
In FIG. 1, when the user operates the portable information communication terminal 10 to start the communication software, the mobile phone 12
Make a call to the center side B via the ET (step S
1). As a result, when the ring signal RING and the calling number CALLING ID are notified to the center side B, these signals are taken into the server 20 via the mobile phone 22 and the data communication adapter 21. The CPU 200 controls the mobile phone 22
While maintaining the on-hook state of, the hard disk 204 is accessed with reference to the calling number CALLING ID (step S2), and the password and the mail file are read. Then, the CPU 200 transfers these to the RAM 201, and prepares for password authentication and mail file transfer (step S3). Here, if the calling number CALLING ID is “030123456”, the display 20
3 displays the screen shown in FIG. That is, the display 203 displays "RING" and "CALLING ID = 030123456"
Is displayed, the system operator can know the communication state.

Thereafter, the CPU 200 sets the mobile phone 22
Is controlled to change from the on-hook state to the off-hook state, a communication line is connected to the terminal A, and a response signal is immediately transferred to the terminal A (step S4). Since charging starts at this point, the above-described step S3
You will not be charged in the preparation stage. Next, when the response signal is detected by the portable information communication terminal 10 on the terminal side A, the portable information communication terminal 10 transfers the password to the center side B (step S5). In the server 20 of the center B receiving this, the CPU 200 performs an authentication process by comparing the password stored in the RAM 201 with the transferred password (step S6).

Here, if the passwords match,
The CPU 200 reads out the mail file stored in the RAM 201 and transfers it to the terminal A (step S7). In this case, there is no need to read the mail file from the hard disk 204, so that the processing time can be reduced and billing can be saved. On the other hand, if the passwords do not match, the CPU 200 transfers an error message to the terminal A (step S8).

When the mail file or the error message is transferred to the terminal side A, the portable information communication terminal 10 controls the portable telephone 12 from the off-hook state to the on-hook state, and the communication ends.

As described above, according to the present embodiment, the calling number CA
Since the LLING ID is used in place of the user ID, there is no need to notify the user ID from the terminal side A to the center side B, and the billing period can be shortened. When the terminal A notifies the center B of the calling number CALLING ID when making a call, the server 20 sets the calling number CA in an on-hook state.
Since the hard disk 204 is searched based on the LLING ID, the password and the mail file registered in advance are read, and the password authentication preparation and the mail file transmission preparation are performed, the billing period can be shortened. Furthermore, if the password is transmitted even if there is no mail transmission request from the terminal side A, the authentication processing is performed and the mail file is immediately transferred, so that the communication time required for the mail transmission request can be reduced. As a result, data communication can be performed at low cost. Specifically, the transfer of the mail file can be performed in about 4 seconds, and the data communication charge can be suppressed to the minimum charge of 10 yen (within 12 seconds).

B. Second Embodiment In the first embodiment described above, one password is assigned to one calling number. However, there are cases where a mobile phone is desired to be shared by a plurality of users. For example, daily work is performed using each individual's personal computer,
This is a case where a common portable information communication terminal is used when making an assertion to a customer or the like. The second embodiment relates to a data communication system corresponding to such a business form, and differs from the first embodiment in that a plurality of passwords are assigned to one calling number.

The overall configuration of the data communication system of the second embodiment is the same as the configuration of the first embodiment shown in FIG. 1, and the configuration of the server 20 is also the same as the configuration of the first embodiment shown in FIG. It is. However, the configuration of the hard disk 204 is different from that of the first embodiment. This will be described with reference to FIG.

FIG. 6 is an explanatory diagram showing the contents of a hard disk according to the second embodiment. As shown in the figure, the storage area of the hard disk is divided for each calling number CALLING ID, and each of the storage areas F1 to Fn stores a plurality of passwords registered in the center B in advance and a mail file corresponding to each password. Is stored.

Next, the operation of the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the operation of the data communication system according to the second embodiment. In the figure, first, when a ring signal RING and a calling number CALLING ID are notified when a call is made from the terminal side A to the center side (step S10), the server 20 keeps the calling number CALLING in the on-hook state. Hard disk 204 based on ID
(Step S11), and the entire corresponding file is copied to the RAM 201 (step S12).

For example, if the contents of the hard disk 204 are as shown in FIG. 6 and CALLING ID1 is transferred as the calling number, the entire data stored in the storage area F1 is copied to the RAM 201. Therefore, CALL
All sets of passwords and mail files corresponding to ING ID1 are prepared in advance.

Next, when a response signal is transmitted from the center side B to the terminal A, the portable information communication terminal 10 detects this and transmits a password to the center side C (step S1).
4). Thereafter, the CPU 200 of the server 20 compares the received password with a plurality of passwords stored in the RAM 201, and determines whether or not there is a match (step S15). If there is a match, the mail file corresponding to the authenticated password is transferred to the terminal side A. For example, if the contents of the hard disk 204 are as shown in FIG. 6 and the received password is “ghijkl”, the server 20 transmits the mail files M1 ′, M2 ′, M3 ′ to the terminal side A. On the other hand, if there is no matching password, an error message is transmitted from the center side B to the terminal side A.

As described above, according to the second embodiment, a plurality of passwords can be assigned to one calling number CALLING ID, so that a plurality of users can share a portable information communication terminal, Communication can be performed at low cost.

C. Third Embodiment In the second embodiment, since a plurality of passwords are assigned to one calling number CALLING ID, if the received password matches one of the prepared passwords, the user is authenticated as a valid user. However, such authentication reduces security. Thus, in the third embodiment, a sub-ID is prepared, and a password corresponding to the sub-ID is authenticated.

The overall configuration of the data communication system of the third embodiment is the same as the configuration of the first embodiment shown in FIG. 1, and the configuration of the server 20 is the same as the configuration of the first embodiment shown in FIG. It is. However, the configuration of the hard disk 204 is different from that of the first embodiment. This will be described with reference to FIG.

FIG. 8 is an explanatory diagram showing the contents of a hard disk according to the third embodiment. As shown in the figure, the storage area of the hard disk is divided for each calling number CALLING ID, and each of the storage areas F1 to Fn is further divided for each sub ID. One password and one or more mail files are stored in association with each sub ID. In this example, the password abcdef is associated with the sub ID1 = 0001, and the mail files M1, M2, etc. are associated. Therefore, referring to the calling number CALLING ID, the hard disk 2
If you access 04, you can get the sub ID, password and mail file.

Next, the operation of the third embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the data communication system according to the third embodiment. Steps S10 to S14 are the same as those in the flowchart of the second embodiment shown in FIG. 8, and thus description thereof will be omitted.

In the figure, when a response signal is transmitted from the center side B to the terminal A, the portable information communication terminal 10 detects this and transmits a sub-ID and a password to the center side C (step S18). In this case, the sub ID and the password are stored in the memory inside the portable information communication terminal 10, and when the CPU detects the response signal, it reads out the response signal from the memory and transmits it. After this, the server 20 C
The PU 200 acquires the password corresponding to the received sub ID from the RAM 201, and determines whether or not this password matches the received password (Step S).
19). In this case, since it is not necessary to access the hard disk 204 to perform password authentication, authentication processing can be performed at high speed.

If the passwords match, the determination is YES, and the mail file corresponding to the authenticated password is transferred to the terminal A (step S20). For example, if the contents of the hard disk 204 are as shown in FIG. 8 and "CALLING ID1" has been received as the calling number, "0001" has been received as the sub-ID, and "abcdef" has been received as the password, the server 20 sends the mail file M1 , M2 to the terminal side A. On the other hand, if the passwords do not match, NO is determined, and an error message is transmitted from the center side B to the terminal side A (step S21).

As described above, according to the third embodiment, since a plurality of sub-IDs and passwords are assigned to one calling number CALLING ID, security can be enhanced by performing password authentication for each sub-ID. Also, a portable information communication terminal can be shared by a plurality of users, and data communication can be performed at low cost.

3. Modifications The present invention is not limited to the embodiments described above,
For example, various modifications described below are possible. In each of the embodiments described above, a portable information communication terminal is described as an example of a terminal that performs data communication. However, the present invention is not limited to this, and a notebook personal computer may be used. In short, any device may be used as long as it performs data communication via a communication network.

In each of the above-described embodiments, the portable information communication terminal 10 may be capable of selecting the conventional data communication or the data communication described above. For example, if there is a server X that performs the conventional data communication and a server Y that performs the above-described data communication, if a call is made by designating the telephone number of the server X with the portable information communication terminal 10, When a call is made by selecting a script file that conforms to the communication protocol described above and specifying the telephone number of the server Y with the portable information communication terminal 10 to make a call, the script file that conforms to the communication protocol described above is selected and communicated. What should I do? In short, a script file may be prepared for each server, and the script file may be switched according to the selected server.

In each of the embodiments described above, the password authentication processing is performed. However, the present invention is not limited to this, and the password authentication processing may be omitted. In this case, the mail file and the calling number are stored in the hard disk 204 of the server 20 in association with each other. Then, when receiving the calling number when making a call from the terminal side A, the server refers to the calling number, reads out the corresponding mail file from the hard disk 204, transfers the mail file to the RAM 201 and transfers the data to the RAM 201 in the on-hook state. Prepare for transmission. After the reading is completed, the on-hook state is switched to the off-hook state, and the prepared mail file may be transmitted to the terminal side A.

In each of the above embodiments, the transfer of the mail file has been described as an example of the data transfer.
The present invention is not limited to this. For example, data of facsimile communication may be used, and it goes without saying that the type of data is not limited.

[0043]

As described above, according to the present invention, since data transmission can be prepared in the on-hook state, data transmission can be performed immediately when the server is switched from the on-hook state to the off-hook state. It is possible to reduce the connection time to be charged.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a data communication system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a server according to the embodiment.

FIG. 3 is an explanatory diagram showing contents of a hard disk according to the embodiment;

FIG. 4 is a sequence diagram showing an operation of the data communication system according to the embodiment.

FIG. 5 is a diagram showing an example of a screen of a display according to the embodiment.

FIG. 6 is an explanatory diagram showing contents of a hard disk according to a second embodiment.

FIG. 7 is a sequence diagram showing an operation of the data communication system according to the embodiment.

FIG. 8 is an explanatory diagram showing the contents of a hard disk according to a third embodiment.

FIG. 9 is a sequence diagram showing an operation of the data communication system according to the embodiment.

[Explanation of symbols]

Reference Signs List 10 portable information communication terminal (terminal, calling number notification means, password notification means, storage means, notification means) 20 server 200 CPU (reading means, preparation means, data transmission means, response means, authentication means) 201 RAM (preparation means) 204) Hard disk (storage means) NET communication network (telephone communication network) CALLING ID Calling number

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yuko Sasahara 2-10-1 Toranomon, Minato-ku, Tokyo Inside NTT Mobile Communication Network Co., Ltd.

Claims (5)

[Claims] 1. A data communication system for performing data communication via a communication network that is charged when an off-hook state is set, a terminal for notifying a calling number when making a call, and data associated with the calling number. Storage means for storing;
When the calling number is received from the terminal, the reading means refers to the calling number and reads data corresponding to the calling number from the storage means while the on-hook state remains. A data transmission system for switching to a state and transmitting data read to the terminal. 2. A data communication system for performing data communication via a communication network in which charging is performed when a terminal and a server go off-hook, wherein the terminal sets a calling number of the terminal when making a call. A calling number notifying unit for notifying, a storing unit for storing a password, and a password notifying unit for reading out the password from the storing unit when detecting a response signal from the server and notifying the server of the password, The server stores a password and data registered in advance in association with the calling number, and, upon receiving the calling number from the terminal, refers to the calling number in an on-hook state and responds to the calling number. Preparation means for reading passwords and data from the storage means to prepare for password authentication and data transmission; and A response unit that switches from an on-hook state to an off-hook state after completion, and notifies the terminal of the response signal; and, upon receiving a password from the terminal, performing authentication based on the received password and the prepared password. Means, if the authentication means is authenticated,
A data communication system, comprising: data transmission means for transmitting prepared data to the terminal. 3. In a data communication system for performing data communication via a communication network in which charging is performed when an off-hook state is established between a terminal and a server, the terminal sets a calling number of the terminal when making a call. A calling number notifying unit for notifying, a storing unit for storing a password, and a password notifying unit for reading out the password from the storing unit when detecting a response signal from the server and notifying the server of the password, The server is configured to store a plurality of passwords and data registered in advance in association with the calling number, and, upon receiving the calling number from the terminal, refer to the calling number while in an on-hook state. Preparation means for reading a plurality of corresponding passwords and data from the storage means and preparing for password authentication and data transmission; After the preparation is completed, switching from an on-hook state to an off-hook state, and responding means for notifying the terminal of the response signal, upon receiving a password from the terminal, based on the received password and a plurality of prepared passwords, An authentication unit for performing an authentication process, and when the authentication unit is authenticated as valid,
A data transmission unit for transmitting prepared data corresponding to the authenticated password to the terminal. 4. A data communication system for performing data communication through a communication network in which charging is performed when a terminal and a server go off-hook, wherein the terminal sets the calling number of the terminal when making a call. A calling number notifying means for notifying, a storing means for storing a password and a sub-ID, a notice for reading out the password and the sub-ID from the storing means when detecting a response signal from the server, and notifying the server of the password and the sub-ID Storage means for storing a plurality of passwords, sub-IDs, and data registered in advance in association with the calling party number, and when the calling party number is received from the terminal, remains on-hook. , Referring to the calling number, reading a plurality of passwords, sub-IDs, and data corresponding to the calling number from the storage means, Preparation means for performing certificate preparation and data transmission preparation, after the preparation is completed, switching from an on-hook state to an off-hook state, a response means for notifying the terminal of the response signal, and a sub-ID and a password from the terminal. Upon receipt, based on the prepared password corresponding to the received sub-ID and the received password, an authentication unit for performing an authentication process, and if the authentication unit is authenticated as valid,
A data transmission unit for transmitting prepared data corresponding to the authenticated password to the terminal. 5. A data communication method for performing data communication between a terminal and a server via a telephone communication network, wherein when a call is made from the terminal to the server, a calling number of the terminal is transmitted to the server. When the server receives the calling number from the terminal, the server performs, in an on-hook state, a preparation for authenticating a password corresponding to the calling number and a preparation for transmitting data corresponding to the calling number. After completing the authentication preparation and the transmission preparation, switch from an on-hook state to an off-hook state, transmit a response signal to the terminal, and when the terminal detects the response signal, transmit a password to the server. The server performs an authentication process based on the received password and the prepared password. A data communication method comprising transmitting prepared data to the terminal when the terminal is authenticated.