JP3408495B2 - How to prevent double notification of retransmitted messages - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of receiving a message from an external device and notifying the application program, and more particularly to a method of preventing duplicate notification of the message retransmitted by the external device due to a timeout to the application program.

[0002]

2. Description of the Related Art In recent years, in communication in a terminal (DTE) such as a personal computer, a processor dedicated for communication is mounted for communication control for the purpose of speeding up / enhancing the CPU and reducing the cost of the system. The control by the communication board (intelligent control) is shifting to the direct control by the CPU (non-intelligent control).

[0003]

The problem to be solved by the present invention is that when a CPU-intensive process such as moving image reproduction or reading / writing from / to an external storage device such as DISK is continuously performed, The time allotted to the communication control is reduced, and as a result, it takes much time to retrieve data from the reception buffer in the reception process.

At this time, the external device does not receive the response of the transmission message even after a certain period of time, and it is considered that the communication error (no-response timer timeout) occurs on the external device side and the message is lost during the communication. , As the recovery process, the same message as the one previously transmitted is transmitted.

FIG. 5 shows an operation diagram in the case of notifying the application program of reception in duplicate.

However, in reality, since the DTE side cannot acquire the CPU time in the communication control, it takes only a long time to transfer the data from the reception buffer. Therefore, after the data transfer, the application program is notified of the reception of a message. , After sending the response message to the external device, it waits for the next reception.

At this time, if the re-transmitted text sent from the external device is stored in the reception buffer, the communication control erroneously recognizes that the next received text has arrived, and after the reception processing, the received text is received by the application program. Will be notified. The application program that receives this notification causes a communication inconsistency with the external device.
This inconsistency sometimes makes subsequent communication illegal, resulting in communication failure or communication sequence abnormality, which affects the operation of the application program.

In this case, if it can be modified including the external device side, it can be avoided by modifying the communication message (such as embedding a sequential number in an unused place in the message) or increasing the transmission timeout time. Although it is possible, some modification is required on the external device side, which results in a conflict with the original idea of reducing the cost of the system. In addition, when it is not possible to deal with it due to other factors (when updating the DTE, only external devices are continuously used from the old system, but the number of external devices is large and they are installed in a distributed manner, or the external devices are old-fashioned. It is difficult to avoid such cases).

It is an object of the present invention to provide a re-transmission message double notification prevention method which makes it possible to prevent double notification of a message retransmitted from an external device to an application program.

[0010]

According to the method for preventing double notification of re-transmission message according to the present invention, the actual reception time required for reading a message from the reception buffer becomes a reference for the external device to start the retransmission of the message. A first determining step of determining whether it is longer than a receivable time, and a setting step of storing the electronic message and setting a re-transmission statement waiting state when the receiving time is longer than the receivable time, A second determination step of determining whether or not the message received at this time is the same as the stored message if a message is received when the re-transmitted message waiting state is set.
If the result of the second determination step is affirmative and the re-transmission sentence waiting state is set,
And a stop step of stopping notifying the application program of the received electronic message.

Further, the method for preventing double notification of re-transmission message according to the present invention is the above method for preventing double notification of re-transmission message, wherein the receivable time is the data length of the message read from the buffer, the external device and the message. It further comprises a calculation step of calculating from a communication speed with the receiving terminal, a timeout time for the retransmission of the external device, and a response logical time required for a response from the terminal to the external device.

Further, the method for preventing double notification of re-transmission sentence according to the present invention further comprises the step of canceling the re-transmission statement waiting state when a predetermined time has elapsed after the setting in the method for preventing double notification of re-transmission sentence. It is characterized by having.

Further, in the method for preventing double notification of re-transmission message, the method for preventing double notification of re-transmission message does not transmit a message even when a request is made from the application program when the re-transmission statement waiting state is set. It is characterized by

In the computer-readable recording medium according to the present invention, is the actual reception time required for reading the message from the reception buffer longer than the receivable time which is a reference for the external device to start the retransmission of the message? A first determination step of determining whether or not there is a setting step of storing the message and setting a re-transmission statement waiting state when the reception time is longer than the receivable time; If a telegram is received while the message is being displayed, a second decision step of deciding whether or not the telegram received at this time is the same as the stored telegram, and the decision in the second decision step When the result is positive,
If the re-transmission message waiting state is set, a program for causing the computer to execute the re-transmission message double notification prevention method having a stop step of stopping notifying the application program of the received message is recorded. It is characterized by

A computer-readable recording medium according to the present invention is the above-mentioned computer-readable recording medium, wherein the method provides the receivable time,
The data length of the electronic message read from the buffer, the communication speed between the external device and the terminal that receives the electronic message, the timeout time for retransmission of the external device, the response logic required for a response from the terminal to the external device. It is characterized by further comprising a calculation step of calculating from time.

Further, in the computer-readable recording medium according to the present invention, in the above-mentioned computer-readable recording medium, the method releases the re-transmission message waiting state if a predetermined time has elapsed after the setting. Is further included.

Further, in the computer-readable recording medium according to the present invention, in the above-mentioned computer-readable recording medium, even when there is a request from the application program when the method is set to the re-transmission statement waiting state. It is characterized by not sending a telegram.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a data terminal device (DTE) shown in FIG.
This is to prevent the DTE side from mistakenly regarding the re-transmission statement sent by the external device as the next message and notifying the application program to the no-response timer timeout caused by the delay in data transfer in the DTE. is there.

The non-response timer timeout time on the external device side and the logical time required for message reception (communication speed x received message length) are added, and the logical time required for response transmission is subtracted from that time, and the receivable time is actually calculated. Compare the actual reception time required to receive, and if the actual reception time is larger than the receivable time, as a double notification prevention measure, the message reception notification of the message that will be retransmitted after notification to the application program It waits for reception, and if received, discards it.

During the meantime, if a transmission request is received from the application program, the execution of the transmission process is awaited,
The transmission process is performed after the reception of the re-transmitted text is completed.

The no-response timer timeout time, the communication speed, and the response transmission logic time on the external device side each have a value inside the communication control and correspond to changes in the system environment. Further, it is possible to correspond to a plurality of external devices by having these values independently for a plurality of external devices.

FIG. 1 shows the overall configuration of the system.

This method uses the application program 1
It operates on a system composed of a DTE composed of the communication control unit 2 and the reception buffer 3 and an external device 4 connected to the DTE by communication.

The application program 1 is an application program for performing data communication with the external device 4. By sending a transmission request 11 to the communication control 2 when data transmission to the external device 4 becomes necessary. Data transmission is requested, and the transmission result is confirmed by the transmission result 22. Further, when the electronic message reception notification 23 is received, it is considered that the data reception from the external device 4 has occurred, and the corresponding processing is performed based on the data.

The communication control unit 2 controls transmission / reception of communication, and requests transmission 11 from the application program 1.
When the message is received, the transmission message 21 is transmitted to the external device 4, and the response is notified from the reception buffer 3 as the response message 41. Therefore, the result is notified to the application program 1 as the transmission result 22. When data reception occurs, the reception telegram 42 from the reception buffer 3 is received, it is confirmed whether the reception telegram is correct, and the result is transmitted to the external device 4 as the response telegram 24. When the received message is correct, the message reception notification 23 is notified to the application program 1.

The reception buffer 3 temporarily holds a reception message from the external device 4, and is for filling the performance difference between the reception process of the communication control unit 2 and the transmission process of the external device 4. The reception buffer 3 receives the response message 31 or the reception message 32 from the external device 4 and stores it.

When the external device 4 receives the transmission message 21 transmitted from the communication control unit 2, it transmits the response message 31 to the reception buffer 3. Further, when some transmission factor occurs in the external device 4, the reception message 32 is created and transmitted to the reception buffer 3, and the response message 24 from the communication control unit 2 is generated.
The external device 4 by receiving the response message 24
Ends the transmission processing from.

If the response message 24 is not notified from the communication control unit 2 even after a lapse of a certain time after the message is transmitted (no-response timer timeout), the external device 4 considers that the received message 32 has disappeared on the line. , The reception message 32 is transmitted again, and the response message 24 is waited for.

FIG. 2 is a detailed block diagram of the communication control reception process for explaining the operation of the embodiment.

The communication control unit 2 calls the reception process shown in FIG. 3 when a message reception factor occurs.

In the reception process, the reception state 81 is confirmed, and when the reception state 81 is the "re-transmission statement waiting state", it is judged whether the timeout occurs by looking at the re-transmission statement waiting timer 82. If the timeout occurs, , Reception status 81
To change step A10. If not, the process proceeds to the next step A2. Reception status 81
Is not in the re-transmission statement waiting state, the process proceeds to the next step A2 (A1). In addition, the re-transmission statement waiting state is step A.
9 is set to the "re-transmission statement waiting state", and is set to the "released state" in steps A8 and A10.

Next, the reception start time 71 is acquired (step A2).

Next, the reception data 61 is acquired and the reception data length 62 is added until the reception message is completed (step A3). The acquired received data 61 is stored in the bank of the secondary buffers of the two banks in which the last received telegram is not stored, and is the object of comparison in step A5.

When the received telegram ends, the end time 72 is acquired, the end time 72 is subtracted from the start time 71 acquired in step A2, and the actual reception time 73 is calculated (step A4).

Next, if the reception state 81 is the "re-transmission message waiting state", it is confirmed whether the current reception message is the same as the previous reception message, and if it is the same, the application program is notified of the reception message received this time. Avoid doing
In addition, in order to change the reception state 81 to the release state, step A
The process proceeds to 10 (step A5).

Next, the logical reception time 54 is obtained from the received data length 62 and the communication speed 51 by the logical reception time = received data length / communication speed, and the logical reception time 5
By adding the non-response timer timeout time 52 of the external device to 4, the receivable logical time 55 is obtained. Furthermore, the receivable time 56 is obtained by subtracting the response transmission logical time 53, which is the time required to transmit the response message to the external device 4, from the receivable logical time 55 (step A6).

Next, the actual reception time 73 and the receivable time 56
If the actual reception time 73 is shorter than the receivable time 56, it is regarded as a normal communication state and the process branches to step A8. If the actual reception time 73 is long or equal, a data transfer delay occurs. It is considered and the process branches to step A9 to shift to the re-transmission statement waiting state (step A7).

In step A8, the message reception notification 23 is transmitted to the application program (AP) 1, the response message 24 is transmitted to the external device 4, and if the reception state 81 is the "re-transmission message waiting state", "release" is issued. State ",
The setting of the re-transmission sentence waiting timer 82 is canceled.

In step A9, the electronic message reception notification 23 is transmitted to the application program 1, the response electronic message 24 is transmitted to the external device 4, and the electronic message received this time is saved in the secondary buffer. The re-transmission sentence waiting state "is set, and the re-transmission sentence waiting timer 82 (the timer value is set to the non-response timer timeout time 52 of the external device 4 by design, but may be any other value).

In step A10, the reception state 81 is changed from the "re-transmission message waiting state" to the "release state", and the setting of the re-transmission sentence waiting timer 82 is released. The communication control unit 2
Does not prohibit data transmission to the external device 4 when the reception state 81 is in the "re-transmission message waiting state", and does not prohibit data transmission to the external device 4 in the "released state". After the state 81 becomes the “released state”, the communication control unit 2 transmits the data to the external device when the application 1 requests the transmission of the data. When the communication control unit 2 prohibits the data transmission when the reception state 81 is the “re-transmission statement waiting state”,
This is to prevent the resending process from being interrupted if data is received while the external device 4 is performing the resending process when the external device 4 is not intelligent.

Explaining the flow of the above processing, when the reception processing is not delayed, the processing ends through (A8) and the setting for preventing double notification is not made. When the reception process is delayed, the process is (A
9) and the setting for preventing double notification is performed. When the reception process is delayed and the message is retransmitted, the process proceeds from (A5) to (A10), the retransmitted message is not transmitted to the application program, and the setting for preventing double notification is set. It will be canceled. Even if the reception process is delayed, if there is no message resend, the process proceeds from (A1) to (A10), and the setting for preventing double notification is canceled.

FIG. 4 shows an operation diagram when the present invention is carried out.

By setting the no-response timeout time, the communication speed, and the response transmission time for each communication resource, it is possible to suppress double notification that occurs in different communication resources with a plurality of external devices.

When the response time is short due to high-speed communication or the like, it is also possible to judge only the logical receivable time without calculating the response transmission logical time in the calculation of the receivable time.

The method performed by the communication control unit 2 is performed by the computer reading and executing a recording medium recording a program for executing the method performed by the communication control unit 2 by the computer.

[0046]

By implementing the present invention, it is possible to prevent the duplicate notification of the re-transmitted text at the time of no response from occurring on the external device side, and to prevent the illegal operation of the application program by receiving the illegal electronic text. Can be prevented. Further, since the present invention does not touch the external device side, it is possible to correspond to the communication with the external device in which it is impossible to change the setting of the no-response timer timeout time due to factors such as an old model.

[Brief description of drawings]

FIG. 1 is a first block diagram illustrating a communication control unit that performs a re-transmission sentence duplicate notification prevention method according to an embodiment of the present invention, a computer that performs the method, and an external device that communicates with the computer.

FIG. 2 is a second block diagram illustrating a communication control unit that performs the re-transmission sentence double notification prevention method according to the embodiment of the present invention, a computer that performs the method, and an external device that communicates with the computer.

FIG. 3 is a flowchart illustrating a flow of a re-transmission sentence double notification prevention method according to an exemplary embodiment of the present invention.

FIG. 4 is a sequence diagram showing signals communicated among an application program, a communication control unit, a reception buffer, and an external device when the method of double notification of re-transmission sentence according to the embodiment of the present invention is implemented.

FIG. 5 is a sequence diagram showing signals communicated among an application program, a communication control unit, a reception buffer, and an external device when the re-transmission message double notification method according to the conventional example is implemented.

[Explanation of symbols]

1 application program 2 Communication control unit 3 Receive buffer 4 External device

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Claims (8)

(57) [Claims] 1. A first judgment for judging whether or not an actual reception time required for reading a message from a reception buffer is longer than a receivable time which is a reference for an external device to start resending the message. A step of storing the message and setting a re-transmission statement waiting state when the reception time is longer than the receivable time; and receiving a message when the re-transmission statement waiting state is set. If so, a second determination step of determining whether or not the electronic message received at this time is the same as the stored electronic message, and when the determination result in the second determination step is affirmative, If the re-transmission statement waiting state is set,
A re-transmission message double notification prevention method comprising: a stop step of stopping notifying the application program of the received message. 2. The re-transmission message double notification prevention method according to claim 1, wherein the receivable time is a data length of a message read from the buffer, and communication between the external device and a terminal receiving the message. The method for preventing double notification of re-transmitted text further comprising a calculation step of calculating from a speed, a timeout time for retransmission of the external device, and a response logic time required for a response from the terminal to the external device. 3. The method for preventing double notification of re-transmission sentence according to claim 1 or 2, further comprising the step of canceling the re-transmission sentence waiting state if a predetermined time has elapsed after the setting. Retransmission sentence double notification prevention method. 4. The method for preventing double notification of re-transmission sentence according to any one of claims 1 to 3, wherein when the re-transmission sentence waiting state is set, a message is transmitted even if a request is made from the application program. A method for preventing double notification of retransmitted text, characterized by not transmitting. 5. A first determination for determining whether or not an actual reception time required for reading a message from a reception buffer is longer than a receivable time which is a reference for an external device to start resending the message. A step of storing the message and setting a re-transmission statement waiting state when the reception time is longer than the receivable time; and receiving a message when the re-transmission statement waiting state is set. If so, a second determination step of determining whether or not the electronic message received at this time is the same as the stored electronic message, and when the determination result in the second determination step is affirmative, If the re-transmission statement waiting state is set,
A computer-readable recording medium, which stores a program for causing a computer to execute a re-transmission message double notification prevention method, which includes a stop step of stopping notifying an application program of a received message. 6. The computer-readable recording medium according to claim 5, wherein the method sets the receivable time to the data length of a telegram read from the buffer, the external device and a terminal receiving the telegram. A computer-readable recording medium, further comprising a calculation step of calculating from a communication speed between terminals, a timeout time for retransmission of the external device, and a response logical time required for a response from the terminal to the external device. 7. The computer-readable recording medium according to claim 5, wherein the method further comprises a step of canceling the re-transmission statement waiting state if a predetermined time has elapsed after the setting. Characteristic computer-readable recording medium. 8. The computer-readable recording medium according to claim 5, wherein when the method is set to the re-transmission statement waiting state,
A computer-readable recording medium, which does not transmit a telegram even when requested by the application program.