JPH06232946A - Data communication system - Google Patents

Abstract

PURPOSE:To reduce the communication traffic between POS terminal equipments. CONSTITUTION:A transmission data counter 22 storing a value of CNT =[Rs-Ns]-1 is provided in the X.25 module 20 in the POS communication system in which data packets are sent continuously, where Ns is a count of transmission data and Rs is a reception count from an opposite terminal equipment. Then an application section 20 references a count CNT of the transmission data counter 22 in response to the reception of a reception reply data packet RR to confirm the transmittal of a series of transmission data packets DT.

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 using an information processing terminal represented by a POS terminal, and more particularly to a data communication system having a communication protocol capable of continuously transmitting datagrams represented by packets. It is a thing.

[0002]

2. Description of the Related Art Generally, in a data communication system, the system is divided into several layers, and a communication protocol with a partner terminal device is determined for each layer. Data transmission confirmation and retransmission processing are performed between the layers according to the respective communication protocols. Then, although the transmission / reception data is exchanged between the adjacent layers, it does not care how the adjacent layer communicates with the partner terminal device.

An example of such a data communication system is a POS (Point of Sales) communication system. As an example of the communication protocol, the POS communication system uses X. 25 protocols are used.

FIG. 5 is a system configuration diagram showing the concept of such a POS communication system. Referring to FIG. 5, P
The OS communication system includes a plurality of Ps connected to the communication line C.
Includes OS terminal devices A and B. It should be noted that FIG. 5 shows only two POS terminal devices A and B for simplification of description. The POS terminal devices A and B are installed in sales floors such as department stores and supermarkets, and can immediately collect data used for single item management, customer management, and the like. This P
The OS terminal device generally has a registration function, a file function for temporarily storing data, an online function for connecting to a host device, and the like. Each of the POS terminal devices A and B
The data communication system includes an application program layer 1, X. 25 program layer 2, HDLC (High l
It is divided into the layer (3) and the interface section (4). A communication protocol is determined between the corresponding layers of each terminal device. That is, between the application program layers 1, the AP protocol, X. X.25 between the 25 program layers. 25 protocols, H between HDLC layers 3
The DLC protocol is defined.

Here, X. 25 protocol is CCI
It is a communication protocol for a packet switching network according to the TT recommendation.

In the POS communication system of FIG. 5, assuming that the transmission side is the POS terminal device A and the reception side is the communication terminal device B, the transmission data is the application program layer 1 → X. 25 program layer 2 →
HDLC layer 3 → interface layer 4 → communication line C → P
Interface unit 4 of OS terminal device B → HDLC layer 3
→ X. 25 program layer 2-> application program layer 1 flows. In this case, as described above, H
DLC layer or X. The 25 program layer has a protocol defined for resending and delivery confirmation at the time of error, but the application program layer 1 has no defined protocol. The application program layer 1 forms a data packet as shown in FIG. 6 and confirms delivery.

FIG. 6 is a diagram showing an example of an application program. Referring to FIG. 6, the transmission data packet includes header 5 and data 6. The header 5 includes information such as communication number, data length, and row address.
In the protocol shown in FIG. 6, the POS communication terminal device A transmits data 1, data 2, and data 3 in this order, and the POS terminal device B receives data 1 and data 2, but receives data 3 correctly. It shows the case where there is not.

When the terminal device B on the receiving side correctly receives the data, the information for confirming the reception of the data is included in the response data packet and returned to the POS terminal device A on the transmitting side, and when there is an error in the received data. That is, when the data cannot be correctly received, the resend request information is included in the response data packet and returned to the POS terminal device A.

[0009] The terminal device A on the transmitting side retransmits the data packet including the data 3 when the resending request signal is included in the received data. When the POS terminal device B correctly receives the retransmitted transmission data, the POS terminal device B returns the reception confirmation information to the POS terminal device A, and when the reception confirmation information is obtained, the POS terminal device A transmits the data transmission end information. Send data packet containing. If the data packet from the POS terminal device B includes the end confirmation information, it can be confirmed that all the data has been delivered.

FIG. 7 is a flow chart for explaining the operation of the application program layer 1 shown in FIG. In addition, in the description after FIG. 25 program layer 2, HDLC layer 3, and interface layer 4 as X.25. 25
It is called a module.

If there is transmission data, the application program 1 executes the X.X. 25. Write the transmission data to the module, X.25. The 25th module transmits the written transmission data to the partner terminal device (steps S1 and S).
2).

In step S3, X. It is determined from the reply from the 25 modules whether or not the transmission data can be written. If the transmission data cannot be written, the transmission data is retransmitted or an error process is performed (steps S4 and S5).

When it is determined in step S3 that the transmission data can be written, the reception data is detected and the content of the reception data is confirmed (steps S6 and S).
7).

Next, in step S8, it is judged whether or not the reception confirmation information is included in the data packet from the receiving terminal device of the other party. If the reception confirmation information is not included, the process is performed in step S9 to receive the reception confirmation information. If the confirmation information is included, it is confirmed in step S10 that the transmission data has been delivered to the partner terminal device.

Next, in step S11, it is determined whether or not there is transmission data to be transmitted next. If there is data to be transmitted, the process returns to step S2, and if it is determined that there is no data to be transmitted, The process ends in step S12.

[0016]

As described above,
In a conventional data communication system represented by a POS communication system, each layer of the communication system has no knowledge of communication protocols of other layers, and therefore, when transmitting data, X. After passing the transmission data to 25 modules,
In order to confirm whether or not the data is correctly sent to the partner terminal, a procedure of exchanging data delivery confirmation information in the upper layer, that is, the application program layer is required. For this reason, there is a drawback in that communication traffic is increased.

Also, if this procedure is not followed, the upper layer judges that the communication is completed at the point when the data transfer from the upper layer to the lower layer is completed, and the lower layer does not send the data, but the end. There is a drawback that data is lost by performing processing.

These are because the communication protocol of each layer is independent of each other and operates asynchronously, so that a time lag occurs in communication between the upper layer and the lower layer.

The present invention has been made to solve the above drawbacks of the conventional data communication system.
It is an object of the present invention to provide a data communication system capable of significantly reducing communication traffic.

[0020]

A data communication system according to the present invention has a communication protocol capable of continuously transmitting data packets between a plurality of terminal devices, and each of the plurality of terminal devices is an application. A first part for executing the program, and a second part provided below the first part for executing the communication program, the second part
Part holds the data number difference between the number of transmitted data packets and the number of received data contained in the response data packet from the partner terminal device with respect to the transmitted data packet, and the first part is for receiving the response data packet. In response, the difference in the number of data held in the second part is checked.

However, the communication protocol is X. 25
It may be a protocol.

[0022]

In the present invention described above, the first part executing the application program checks the difference between the number of transmitted data packets and the received data held by the second part, that is, the difference in the number of data. It is possible to confirm the delivery of the transmitted data. Therefore, it is not necessary to confirm the response from the application of the partner terminal device, and the communication traffic can be significantly reduced. Further, since the contents held in the second part of the own terminal device can be directly referred to, the performance of the entire communication system can be improved as compared with waiting for a response from the application of the partner terminal device. . Further, it is possible to confirm the delivery of the transmission data to the partner side regardless of the load status of various resources of the partner terminal device and the influence of the communication line.
From this, it is possible to prevent the performance of the entire system from deteriorating due to the delay in the reception confirmation response at the application level from the partner terminal device due to the heavy load on the partner terminal device or the deterioration of the communication line quality. You can

As a second part, X. When the 25 protocol is used, the communication traffic in the POS communication system can be significantly reduced.

[0024]

1 is a system block diagram showing an embodiment of a POS communication system according to the present invention.

Referring to FIG. 1, this POS communication system has POS terminal devices A and B connected to a communication line C.
including. The POS terminal device A includes an application unit 10
And X. X.25 for transmitting and receiving data packets DT according to the H.25 protocol. 25 modules 20 and. Since the POS terminal device A and the POS terminal device B have the same configuration, the description of the configuration of the POS terminal device B is omitted.

The application unit 10 includes a register 11 for temporarily holding data to be transmitted and received data. In addition to the registers, it also has various functions for executing application programs.

X. 25 module 20 includes a transmission buffer 21, a transmission data counter 22, and a transmission counter 2.
3, a reception counter 24 is included. The transmission buffer 21 holds the transmission data from the application unit 10 and sends it to the communication line C. This transmission data includes a transmission count value (Ns) if the POS terminal device is the transmission side,
If the POS terminal is the receiving side, the reception count value (R
s) is included. The transmission data counter 22 increments in response to the output of the transmission data of the application unit 10 (CNT ← CNT + 1). The transmission counter 23 also increments the transmission count value Ns of the output packet DT. In the case of modulo 8, the transmission count value Ns is repeated as 0, 1, 2, ..., 6, 7, 0, 1 ,. The reception counter 24 takes in the reception count value Rs set in the reception response packet RR and gives it to the transmission data counter 22.

X. In the 25 protocol, the maximum number of continuously transmitted packets (window size W
s) negotiation and decision. Thereafter, the data packet DT is transmitted / received according to the window size Ws. When the POS terminal device on the receiving side receives the data packet, it must transmit the reception response packet RR. However, when the data packet DT is received, the reception response data packet RR does not need to be transmitted each time each data packet DT is received, and one reception is made for the reception of the data packet DT of the maximum window size Ws. The response can be returned in the response data packet RR. Therefore, when the POS terminal device on the transmitting side receives the reception response data packet RR, if it confirms the content of the reception count value Rs, it transmits how many data packets DT and responds to how many of them with the response from the partner. You can check if there was. Therefore, this transmission count value Ns
And the value of CNT is reduced based on the reception count value Rs.
As a result, CNT = [Rs-Ns] -1. However,
[Rs-Ns] represents the difference between Rs and Ns, and in the case of modulo 8, takes an integer between 1 and 8.

In this way, the application unit 10
After writing all the data in the transmission buffer 21, confirms the transmission data count value CNT, and if CNT becomes 0,
It is possible to know that a response has been returned from the partner terminal for all data. On the other hand, CNT = x (where x is 0
In the case of (not), it indicates that a plurality of data packets DT have been transmitted, but there is no response from the partner terminal device or that the reception response data packet RR has been received only for a part of the transmitted data packet DT. Therefore, it can be seen that the reception response data packet RR from the partner terminal device has not yet been received for some data packets DT.

FIG. 2 is a flow chart showing the program of the application section 10 shown in FIG. Figure 3
X. 25 is a flowchart showing a program of the 25 module 20. Referring to FIG. 2, application unit 10 determines the presence / absence of transmission data in step S1. 25 modules 20 are provided. X. Two
5 module 20 determines whether or not there is a space in the transmission buffer 21, writes the transmission data in the transmission buffer 21 if there is space, and returns the status of transmission buffer full if there is no space (see below Step T1 of 3
T3).

The application section 10 operates in step S3.
In X. The presence or absence of the status from the 25 module 20 determines whether or not the transmission data can be written. If the transmission data cannot be written, the transmission data is retransmitted or an error process is performed (steps S4 and S5). If it is possible to write the transmission data in step S3, it is determined in step S6 whether there is data to be transmitted next. If there is data to be transmitted,
The processes of steps S2 to S5 are repeated. In this way
Detect that you have sent a series of multiple data.

Next, in step S7, the contents of the transmission data counter 22 are read, and in step S8 it is determined whether the count value CNT of the transmission data counter 22 is 0 or not. If the transmission data count value CNT is not 0, the processes of steps S7 and S8 are performed again.

In step S8, the count value C
If NT is 0, it is confirmed in step S9 that all the data has been transmitted to the partner terminal device, and the communication end processing is performed in steps S10 and S11.

With reference to FIG. 25 modules 20
The transmitting operation and the receiving operation will be described. X. In response to the transmission request from the application unit 10, the 25 module 20 determines whether the transmission buffer 21 has a space (T1 and T2). If there is no free space, a transmission signal indicating that the transmission buffer is full is returned to the application unit 10 in step T3. Step T
If it is determined in 2 that the transmission buffer 21 has a space, the transmission data is written in the transmission buffer 21 in step T4.

Next, the transmission count value Ns is set, the transmission data count value CNT is incremented, and the data packet DT is transmitted (steps T5, T6, T7).

After the process of step T7 is completed, the process proceeds to step T1. X. The 25 modules process the received data as follows. In step R1, it is determined whether there is received data, and if there is received data,
In step R2, it is determined whether the received data is the reception response data packet RR. If the received data is not the received response data packet RR, the received data is processed and given to the application unit 10 in step R3. On the other hand, the received data is the received response data packet R
If it is R, the reception count value Rs is confirmed, and in step R5, the transmission data count value CN
The T is decremented, and in step R7, the transmission buffer 21 holding the transmission confirmed transmission data is released. After performing the process of step R7, step R
Go to 1.

As described above, the X. 25 module 20 is an X.25 module of the partner terminal device. The transmission count value Ns and the reception count value Rs are transmitted / received to / from the 25 modules, and CNT = [Rs-Ns] is set in the transmission data counter 22.
Hold the value -1. Then, the application unit 10 calls the count value CNT to confirm the arrival. Therefore, the application unit 1 of the partner terminal device
It is not necessary to confirm the data delivery every time a data packet is transmitted to and from 0. As a result, communication traffic can be significantly reduced.

FIG. 4 shows the count value CNT of the transmission data counter 22 and the transmission counter 2 in the case of modulo 8.
3 count value Ns, reception counter 24 count value R
It is a figure which shows an example of the change of s. However, here, the window size Ws = 3.

Since the window size Ws is set to 3, the maximum value of the transmission data count value CNT becomes 3, and when the reception response data packet RR is received, the CNT
= [Rs-Ns] -1 = 0. Then, [Rs-N
If s] does not become 1, it means that the reception confirmation for all data packets has not been received from the partner terminal device.

[0040]

According to the present invention described above, it is not necessary to confirm the response from the application unit of the partner terminal device.
Communication traffic can be significantly reduced. Also,
Since it is possible to directly refer to the contents held in the important part of its own terminal device, it is possible to improve the performance of the entire communication system as compared with waiting for a response from the application of the partner terminal device.

[Brief description of drawings]

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

2 is a flow chart showing a program of an application unit shown in FIG.

FIG. 3 shows the X. It is a flowchart which shows the program of 25 modules.

FIG. 4 is a diagram showing an example of changes in the count value of a transmission data counter, the count value of a transmission counter, and the count value of a reception counter in the case of modulo 8.

FIG. 5 is a system configuration diagram showing the concept of a conventional POS communication system.

6 is a diagram for explaining a protocol between the application program layers shown in FIG.

FIG. 7 is a flowchart for explaining the operation of the POS communication system shown in FIG.

[Explanation of symbols]

 A, B POS terminal device 10 Application unit 11 Register 20 X. 25 modules 21 transmission buffer 22 transmission data counter 23 transmission counter 24 reception counter CNT transmission data count value Ns transmission count value Rs reception data count value DT transmission data packet RR reception response data packet

Claims (3)

[Claims] 1. A data communication system having a communication protocol capable of continuously transmitting data packets between a plurality of terminal devices, wherein each of the plurality of terminal devices executes a first application program. And a second part provided below the first part for executing a communication program, the second part including the number of transmission data packets and a response from the partner terminal device to the transmission data packets. A data number difference from the number of received data included in the data packet is held, and the first part checks the data number difference held in the second part in response to the reception of the response data packet. A data communication system comprising: 2. The communication protocol is X. The data communication system according to claim 1, which is a 25 protocol. 3. The second part counts the number of transmitted data packets, counts the number of received data included in the response data packet, and calculates the difference between the counted number of transmitted data packets and the number of received data. The data communication system according to claim 1, wherein the data communication system holds.