JP5176973B2 - Communication system, communication method, and communication program - Google Patents

Description

  The present invention relates to a communication protocol when a communication line is low speed and unstable in communication between apparatuses, and relates to a communication system, a communication method, and a communication program.

  In the present invention, the following communication line is particularly assumed.

  (1) A long-distance telephone line or dedicated line has a slow communication speed and is unstable due to disturbances such as noise.

  (2) A wireless device such as a mobile phone or satellite phone, which has a slow communication speed and is unstable due to the communication environment.

  In a communication system in which communication is performed between a transmission-side device and a reception-side device via a communication line, signal attenuation and noise are affected when the communication distance is long, and wireless communication becomes unstable when the radio wave environment is bad.

  The communication device disconnects the line when an abnormality is detected. The communication protocol reconnects to continue communication.

  The communication protocol detects reliable data from transmitted / received data, and retransmits that portion, thereby realizing reliable communication. For this processing, the protocol transmits a block of data (referred to as a frame) to the other party and receives a response from the other party to confirm that the frame has been delivered.

  This will be described with reference to FIG. 9 showing data transmission / reception between apparatuses A and B. In FIG. 9, after transmission / reception of frame 01 is completed, frame A is transmitted from apparatus A, and apparatus B can receive partway through frame 02, but is interrupted due to a line abnormality (here, interruption does not result in disconnection of the line) This refers to a state in which communication abnormality can be recovered).

  Then, when communication becomes possible after a while, the apparatus A side resumes transmission from the frame 02 because there is no response that the frame 02 has been received from the apparatus B. At this time, the illustrated black portion of the frame 02 can be transmitted at the time of the previous connection, but since it can be processed only in units of frames, it is retransmitted for each frame.

  In addition, as a conventional data communication method and transmission / reception apparatus, the thing of patent document 1 was proposed, for example.

Japanese Patent No. 3961128

  As described in FIG. 9, when a communication abnormality occurs, a response from the other party cannot be received, and processing up to the response that has been normally received before that is processed as transmission completion. When communication is possible, transmission starts from the next frame.

  However, when it is disconnected, there is a possibility that a part of the frame or the whole frame has reached the other side, and the data is discarded and wasted because the response has not been transmitted.

  In a line having a high transmission rate or a line having a low speed but a stable communication environment and almost no disconnection, the discarded data is small as viewed from the whole, so that there is no problem. However, the influence of the discarded data is great on a line with a low transmission rate and an unstable line and cannot be ignored.

  In addition, if data of one frame of 1000 bytes is transmitted in an environment where communication becomes unstable in the time of transmission of 1000 bytes, it is spent retransmitting the same frame every time, and communication is only occasionally established.

  There are many examples in which the lower protocol is divided into smaller units and transmitted with respect to the upper protocol. However, they are sizes determined by restrictions due to physical characteristics of transmission and restrictions on the standard, and do not take into account frequent transmission abnormalities. Because the situation of unstable lines varies greatly depending on the environment such as time and place, it is necessary to review the size to be always divided.

  Problems in the conventional communication system and communication method are as follows.

  (1) If communication abnormality occurs in a time shorter than the unit managed by the protocol, transmission will not succeed. It must be able to be divided so that it can be transmitted in a shorter time than the abnormal time. Although there are protocols that are divided into small parts, they are not determined from the frequency of occurrence of transmission abnormalities, and cannot respond to changes in the situation.

  (2) A part of the data that has reached the partner at the time of disconnection is discarded. At the next connection, it is necessary to retransmit the discarded part including the discarded part.

  The present invention solves the above-described problems, and an object thereof is to provide a communication system, a communication method, and a communication program that can follow the deterioration of the transmission state and prevent unnecessary retransmission. It is in.

  In the communication system of the present invention for solving the above-described problem, one frame of data is configured with a predetermined data length, and a frame number indicating what number frame is on the communication line and what number in the frame. A communication system that performs communication via a communication line between a transmission-side apparatus that transmits a block including a block number that represents a block and a reception-side apparatus, provided in the transmission-side apparatus The transmission side control means and the reception side apparatus provided in the reception side apparatus, wherein the transmission side control means has a function of transmitting the block, and a latest version representing the latest transmission frame after the block transmission. A function for transmitting delivery confirmation data including a transmission frame number and a reception completion frame number indicating a reception completion frame at the reception side device, and a frame transmitted from the reception side device. A reception state notification data including a number and a reception block state, and a function of transmitting an unreceived block designated by the data, wherein the reception side control means is a block transmitted from the transmission side device. And when receiving the delivery confirmation data transmitted from the transmission side device, determine a frame that has not been received based on the latest transmission frame number in the data, And a function of transmitting reception state notification data indicating which block of the frame is not received.

  The communication system according to claim 2 is the communication system according to claim 1, wherein the transmission side control means includes the latest transmission frame number and the reception completion frame number, and is a new one generated from a random number at the first connection to the communication line. A connection start notification data to which the connection number at the time of the previous connection is assigned when reconnecting after disconnecting the line, and after receiving the connection start notification data as a response from the receiving side device A function of transmitting the block, and when the reception side control means receives connection start notification data from the transmission side device, whether or not a number that matches the connection number exists in a past communication record. If the connection result is the same as the determination result and the determination result, the reception completion frame number and the latest transmission frame number are taken over from the communication record. A function of adding a new connection number to the communication record when the determination result is that there is no matching connection number, and a function of transmitting notification data of the connection start after taking over or adding the communication record as a response; It is characterized by having.

  According to a third aspect of the present invention, in the communication system according to the first or second aspect, the transmission-side control means transmits reception completion frame data represented by a reception completion frame number in the delivery confirmation data from the transmission-side memory. It has the function to delete.

  According to a fourth aspect of the present invention, in the communication system according to any one of the first to third aspects, the transmission-side control means sets the length of the block to the first block length when connected to the communication line for the first time. And determining the length of the block based on the frequency of occurrence of communication abnormalities collected within the predetermined period, a function for collecting communication abnormalities within the predetermined period, And a function for determining the block length of the block.

  The communication method according to claim 5 is configured such that one frame of data is configured with a predetermined data length, a frame number indicating what number frame is on the communication line, and what number block in the frame. A communication method in a communication system in which communication is performed via a communication line between a transmission-side apparatus that transmits a block including a block number that indicates whether there is a transmission and a reception-side apparatus, The transmission side control means transmits the block, and after the block transmission, the delivery confirmation data including the latest transmission frame number representing the latest transmission frame and the reception completion frame number representing the reception completion frame at the reception side device. A transmitting step, and a receiving-side control means of the receiving-side device receives the block transmitted from the transmitting-side device, and the received block is framed. When receiving the acknowledgment data transmitted from the transmitting side device and determining the frame that has not been received based on the latest transmission frame number in the data, and which block of the frame is not received A step of transmitting reception state notification data indicating whether or not when the transmission side control means receives the reception state notification data transmitted from the reception side device, an unreceived block designated by the data is received. And a step of transmitting.

  The communication method according to claim 6 is the communication method according to claim 5, wherein the transmission-side control means includes the latest transmission frame number and the reception completion frame number, and is generated from a random number at the first connection to the communication line. The connection start notification data to which the connection number at the time of the previous connection is assigned at the time of reconnection after disconnection of the line, and the reception side control means sends connection start notification data from the transmission side device. When receiving a message, a step of determining whether or not a number that matches the connection number exists in a past communication record, and if the determination result is a connection number that matches, a reception completion frame number from the communication record And the step of adding a new connection number to the communication record if the determination result is that there is no matching connection number, Transmitting the connection start notification data after taking over or adding the communication record as a response; and the transmission side control means receives the connection start notification data from the reception side device as a response. And a step of transmitting.

  The communication method according to claim 7 is the communication method according to claim 5 or 6, wherein the transmission-side control means sends reception completion frame data represented by a reception completion frame number in the delivery confirmation data from the transmission-side memory. It has the step to delete, It is characterized by the above-mentioned.

  The communication method according to claim 8 is the communication method according to any one of claims 5 to 7, wherein the transmission side control means sets the length of the block to the first block length at the time of initial connection to the communication line. And determining the length of the block based on the frequency of occurrence of communication abnormalities collected within the predetermined period, the step of collecting communication abnormalities within the predetermined period, And determining the block length.

  A communication program according to a ninth aspect is a communication program that causes a computer to function as each means according to any one of the first to fourth aspects.

  (1) According to the first to ninth aspects of the present invention, since communication is performed in units of blocks obtained by dividing a frame, even if communication fails at intervals shorter than the frame due to instability of the communication line, etc. Can be maintained. In addition, since delivery confirmation data and reception status notification data are used, when the line is disconnected due to a transmission error (communication error), only the partial data (block) that the other party could not receive in the reconnection is retransmitted. You can avoid re-sending.

  That is, the data being transmitted is discarded due to the disconnection, and it is time-consuming to retransmit the entire frame data at the next connection. Since transmission is started from the next block by utilizing, transmission waste is reduced.

  (2) According to the inventions of claims 2 and 6, notification of connection start having connection numbers corresponding to a plurality of connection states, such as when connecting to a communication line for the first time or when reconnecting after disconnecting the line Since data is used, data transmission can be started in an appropriate connection state.

  That is, in order not to perform the above-described useless retransmission, it is necessary to maintain the previous connection state. However, according to the present invention, the connection number corresponding to the plurality of connection states is obtained from the receiving side device at the time of line connection. Since the transmission side device is notified, communication can be resumed by returning to the corresponding connection state. As a result, it is possible to prevent deterioration in transmission efficiency even if line disconnection occurs frequently.

  (3) According to the third and seventh aspects of the present invention, since the reception completion frame number is deleted from the memory using the reception completion frame number in the delivery confirmation data, the memory capacity of the transmission side device It is possible to retransmit unreceived frame data from the transmission side device without increasing the number of frames.

  (4) According to the fourth and eighth aspects of the invention, since management is performed in units (blocks) smaller than the transmission frame, communication can be continued even if a communication abnormality occurs in a short time.

  That is, since the block length is determined according to the frequency of occurrence of transmission abnormality (communication abnormality), the block length is automatically changed according to the transmission state, so the range that can be followed even if the transmission state temporarily deteriorates is wide. Become.

The block diagram which shows the embodiment of the communication system of this invention. Explanatory drawing which shows the block division of the frame applied by this invention. Explanatory drawing which shows the data structure of the block in the example embodiment of this invention. Explanatory drawing which shows the structure of the delivery confirmation data in the example embodiment of this invention. Explanatory drawing which shows the structure of the reception status notification data in the example embodiment of the present invention. The flowchart which shows the process from the block transmission in the example embodiment of this invention to the retransmission of an unreceived block. Explanatory drawing which shows the structure of the notification data of a connection start in the example embodiment of this invention. The flowchart which shows the process at the time of the new connection or reconnection in the embodiment of this invention. Explanatory drawing which shows the malfunction in the conventional communication method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. FIG. 1 is a block diagram showing an embodiment of a communication system according to the present invention, where 100 is a transmission side device, 200 is a reception side device, and 300 is a communication line.

  The transmission side device 100 has a function of transmitting a block obtained by dividing one frame of data into a predetermined data length, and determines the length of the block as a first block length when connecting to the communication line 300 for the first time. Based on a function for performing communication for a predetermined period, a function for collecting communication abnormality within the predetermined period, and a frequency of occurrence of communication abnormality collected within the predetermined period, the block length is set to the second block length. A function for determining, a latest transmission frame number representing the latest transmission frame, and a reception completion frame number representing a reception completion frame in the receiving-side apparatus 200, and a new one generated from a random number at the first connection to the communication line 300 A function of transmitting connection start notification data each of which is given a connection number at the time of the previous connection at the time of reconnection after disconnection of the line; A function of transmitting the block after receiving the connection start notification data as a response; a function of transmitting delivery confirmation data including the latest transmission frame number and reception completion frame number after the transmission of the block; A transmission-side control unit 101 having a function of transmitting an unreceived block designated by the data when receiving the received reception state notification data including the frame number and the reception block state is provided.

  The receiving side device 200 has a function of determining whether or not a number matching the connection number exists in the past communication record when the connection start notification data is received from the transmitting side device 100; If the determination result is that there is a matching connection number, the reception completion frame number and the latest transmission frame number are taken over from the communication record. If the determination result is that there is no matching connection number, a new connection number is stored in the communication record. A function to add, a function to transmit the connection start notification data after taking over or completion of the communication record as a response, and a block transmitted from the transmission side device 100, and assembling the received block into a frame When the function and the delivery confirmation data transmitted from the transmission-side apparatus 100 are received, the data is received based on the latest transmission frame number in the data. A function for transmitting a reception status notification data indicating which block of the frame is not received and a reception completion frame data represented by a reception completion frame number in the delivery confirmation data Receiving-side control means 201 having a function of deleting from the memory.

  The functions of the transmission side control unit 101 and the reception side control unit 201 are achieved by, for example, a computer.

  The communication protocol receives and transmits transmission data from the upper communication layer, and passes it to the upper communication layer when data is received from the communication line. As long as the interface between the upper layer and the lower layer is protected, there is no problem even if the data is divided and managed in the lower layer. Normally, data is divided and transmitted according to physical restrictions and standards of the transmission medium.

  Here, when the frame is transmitted without being divided, if a transmission abnormality occurs in the middle of the frame as shown in FIG. 2, the entire frame can only be discarded. When the frame is divided into small blocks and transmitted while being managed, the frame can be received by retransmitting only 2 blocks and 3 blocks in FIG.

  In the protocol, it is often performed that the data is divided into small units such as blocks. However, there has been no mechanism for adjusting the block length and re-transmission in the present invention as will be described later.

  When the data from the higher order is used as a frame and the divided data is used as a block, transmission will fail if the transmission time of the block is longer than the occurrence interval of communication abnormality. Therefore, in this embodiment, the block length is determined as follows.

  (1) Since the frequency of occurrence of abnormality is unknown at the beginning of connection to the communication line 300, the minimum value (first block length) is set for safety.

  (2) A communication error is collected by operating with the block length (first block length) for a certain period (predetermined period). What is collected is the number of blocks at which abnormalities occur when blocks are transmitted continuously.

  (3) After a certain period, a block length (second block length) is determined from the collected occurrence frequency of communication abnormality. Except for intervals with a low probability of occurrence, the shortest interval is searched for among the remaining intervals, and the block length that can be transmitted within that time is set.

  (4) Once the block length is determined, the next connection is started from the block length (second block length). However, when the time (second predetermined period) has elapsed since the block length (second block length) was determined, the block length is returned to the minimum (first block length).

  Next, the data structure of the block in the present embodiment will be described.

  The block has a structure as shown in FIG. 3, and sets a header at the beginning, a trailer at the end, and data obtained by dividing a frame between them. The frame number and the block number indicate what number frame on the circuit connection is, and what number block is in the frame. The total number of blocks indicates the number of blocks constituting the frame.

  The reason why the total number of blocks is transmitted every time is that it is necessary to know whether it is an entire frame or a part even if only some of the blocks arrive due to a transmission error. Similar processing is possible even when a flag indicating the last block is used instead of the total number of blocks.

  When a communication error occurs, part of the block data is often missing, or abnormal data is added or garbled. For this reason, a simple check code is added to the identification code in the header, and the block is discarded if there is an abnormality on the receiving side. The reason for the simple check code is that the entire frame has a separate check code, so that the completeness of the block unit is not required, and the increase in the block data structure is avoided to complete this.

  Here, the reason for the presence of the trailer in the block of FIG. 3 will be described.

(1) Omission of Data Size As shown in FIG. 2, one frame is composed of a plurality of blocks, and the size of one block is a fixed value determined by the frequency of occurrence of transmission abnormality. For example, when the block size is determined as 300 bytes and the transmission data is 1000 bytes, the block is divided into four of 300 bytes + 300 bytes + 300 bytes + 100 bytes.

  There is no item indicating the size of each block, and the block size other than the last block is 300 bytes. Therefore, the last block handles up to the trailer as block data. Thereby, it is possible to omit sending the frame size and the block size.

(2) Reducing the transmission abnormal timeout On a low-speed and unstable line, timing out without receiving data is time consuming and the transmission bandwidth is degraded. This is because the timeout value cannot be shortened because it is slow and unstable.

  Here, it is assumed that a part of the block data is missing due to a transmission abnormality. If the next block is transmitted after the missing block, the missing data is recognized when the header is received. However, if there is no next transmission, it must be detected by timeout. On the other hand, if the trailer of the present embodiment is used, data loss can be recognized at the time of trailer reception regardless of the data size, so there is no waiting time due to timeout and transmission efficiency is improved.

  The simple check code described above is included in the identification code in the header of FIG. 3, and the identification code is composed of a type and a check code. The type is a code for distinguishing block data, a delivery confirmation described later, a reception state notification, and the like. For example, if the check code is a checksum, a total value from the header to the end of the block data is stored.

  Next, frame synthesis and delivery confirmation data in this embodiment will be described. When receiving the block, the receiving-side apparatus 200 assembles it into a frame, and completes the frame when all the figure locks are aligned. Since it is necessary for the protocol to confirm that the other party has been able to receive, the transmitting apparatus 100 sends delivery confirmation data as shown in FIG. 4 at an appropriate timing.

  In FIG. 4, an identification code is a code indicating the start and end of data, and includes a data type and an overall checksum.

  The duplicate identification is incremented by +1 every time the delivery confirmation data is transmitted. However, when there is no response to the delivery confirmation, the same value is used instead of +1 when the delivery confirmation data is retransmitted due to timeout. That is, it is used for the purpose of preventing the delivery confirmation data from arriving at somewhere on the line and operating erroneously.

  The reception completion frame number represents a reception completion frame in the reception-side apparatus 200, and indicates the last number of consecutive frame numbers in the frame received on the transmission acknowledgment transmission side. That is, it indicates that the next frame has not been received yet or only a part has been received.

  The latest transmission frame number represents the latest transmission frame, and indicates the newest frame number when a plurality of frames are transmitted on the transmission acknowledgment transmission side. In other words, if the other side has received up to that frame, transmission has been completed.

  Next, the reception status notification data in this embodiment will be described.

  When receiving the transmission confirmation data from the transmission-side device 100, the reception-side device 200 determines the following two points based on the data.

  (1) Up to which frame has been received for the frame transmitted from the transmitting apparatus 100.

  (2) Know whether all transmissions from the other party have been received, or whether the next frame has not been received.

  If it is determined that the next frame has not been received, the reception state notification data shown in FIG. 5 is transmitted to the transmission source. The data configuration in FIG. 5 notifies which block has not been received for a frame that has not been received. When receiving the reception state notification data, the transmission side device 100 retransmits the unreceived block to the reception side device 200 to complete the frame assembly.

  That is, in receiving-side apparatus 200, the frame is completed when all the blocks in the frame are aligned by reception, but when all the blocks are not aligned or not received at all, the frame is incomplete.

  When the delivery confirmation data in FIG. 4 is received, the latest transmission frame number of the transmission side device 100 is obtained. This indicates that the frame up to the last block of the frame number has been transmitted, so that an incomplete frame before that frame requests the transmitting side device 100 for a block that is not sufficient by the reception state notification data of FIG. Thereafter, the transmitting apparatus 100 retransmits the missing block to the receiving apparatus 200.

  It is possible to retransmit a block in which a transmission abnormality has occurred by the above processing and perform transmission in units smaller than a frame.

  FIG. 6 shows an example of a flowchart of the processing from the block transmission described above to the retransmission of the unreceived block. In FIG. 6, first, in step S1, the transmission-side apparatus 100 transmits a block.

  Next, in step S2, it is determined whether or not a predetermined time has elapsed. If YES, the process proceeds to step S3, and if NO, the process returns to step S1. In step S3, the delivery confirmation data shown in FIG. 4 is transmitted.

  Next, in step S4, the receiving-side apparatus 200 determines a frame that has not been received based on the latest transmission frame number in the received delivery confirmation data, and receives that indicates which block of the frame has not been received. Send status notification data.

  Next, in step S5, the transmitting apparatus 100 retransmits the unreceived block specified by the received reception status notification data.

  Next, the function using the reception completion frame number in the delivery confirmation data in this embodiment will be described. As described above, when receiving the reception state notification data, the transmitting apparatus 100 retransmits the requested block to the receiving apparatus 200. In order to be able to retransmit any frame at any time, the transmitting apparatus 100 Requires a lot of memory. Therefore, the frame that is known to be completed by the receiving side apparatus 200 is released from the transmitting side memory.

  That is, when a frame is completed by block reception, notification is made with a reception completion frame number in the delivery confirmation data, and the transmission-side apparatus 100 erases data before that frame from the memory. The frame is the last frame continuously received. If there is an incomplete frame, the previous frame number is notified as the reception completion frame number.

  Next, “block transmission from disconnection to reconnection (that is, a mechanism for restarting from the middle in units of blocks even if the line is disconnected in the middle)” in this embodiment will be described.

  When the line is disconnected, the status of the other party (reception side) is unknown, but the transmission / reception status of oneself (transmission side) can be recorded. Transmission is continuously started from the time of disconnection by obtaining the transmission / reception state of the other party (reception side) at the time of reconnection. This is done by the following procedure.

  (1) The delivery confirmation on the own device side (transmission side) is transmitted to the partner (reception side).

  (2) When a delivery confirmation is received, a reception state notification is transmitted (to the transmission side) for a frame that we (the reception side) cannot receive.

  (3) When the reception state notification is received (on the transmission side), retransmission is performed for an unreceived block.

(4) When a delivery confirmation is transmitted due to completion of the frame, the other party starts transmitting the next frame.

  With the above operation, a frame can be transmitted without retransmitting a block that can be received at the previous connection.

  Next, the “mechanism for distinguishing and holding connections” in this embodiment will be described. In connection, there is a connection for the first time and after the previous interruption due to a communication error. In addition, since there are connections with other devices, a means for distinguishing them is necessary to continue the previous connection state.

  Therefore, the connection number generated from the random number at the time of power-on or first connection is transmitted to the other party at the time of connection. The other party searches by that number, finds the state at the previous connection, and uses it. If it is not found in the search, it is treated as a new connection. Therefore, connection start notification data having the structure shown in FIG. 7 is required at the start of connection.

  In FIG. 7, duplication identification is made possible to distinguish even when this data does not reach the other party or retransmitted due to delay.

  The connection number is a number generated by a random number if different communication devices are connected, or if the same device is another connection, and the same number is designated if the connection is reconnected even if disconnected due to a communication error.

  The block length is a size determined from the frequency of occurrence of transmission abnormalities.

  The reception completion frame number, the latest transmission frame number, and the like are the same as the values used in the delivery confirmation data in FIG. With this mechanism, a plurality of devices or the same device can distinguish different connections and continue transmission.

  Here, the “block transmission from disconnection to reconnection” and the “mechanism for distinguishing and holding the connection” have the same timing as the operating packet, and FIG. 8 shows an example of a flowchart of these processes.

  In FIG. 8, first, when the power source is ON or initially connected, the transmission side apparatus 100 sets the connection number of the data shown in FIG. 7 as a new connection number generated from a random number in step S11, and the reception completion frame number and the latest The connection start notification data is transmitted with the transmission frame number set to zero.

  If reconnection after line disconnection is made, in step S12, connection start notification data is transmitted with the connection number of the data shown in FIG. 7 as the connection number at the previous connection.

  Next, in steps S13 and S14, the receiving-side device 200 receives the connection start notification data from the transmitting-side device 100, searches past communication records by the connection number, and the received connection number is in the communication record. It is determined whether or not.

  If not, in step S15, a connection number is added as a new connection to the communication record (an area is prepared on the communication record as a new connection number), and the reception completion frame number and the latest transmission frame number are set to zero. In step S16, the reception completion frame number and the latest transmission frame number are read (taken over) from the communication record.

  Next, in step S17, the receiving-side apparatus 200 transmits connection start notification data after the processing of steps S15 and S16 as a response.

  Next, in step S18, if both parties are new in the transmission side device 100 and the reception side device 200, this is also new, the memory is released according to the reception completion frame number, and the reception state notification data is sent according to the latest transmission frame number. Send.

  Thereafter, a normal transmission / reception state is established.

  In addition, a part or all of the functions of each unit in the communication apparatus of the present embodiment can be configured by a computer program, and the program can be executed using the computer to realize the present invention. The communication of the present embodiment It goes without saying that the procedure in the method can be constituted by a computer program, and the program can be executed by the computer. A program for realizing the function by the computer can be recorded on a computer-readable recording medium, for example, FD (Floppy). (Registered trademark) Disk, MO (Magneto-Optical disk), ROM (Read Only Memory), memory card, CD (Compact Disk) -ROM, DVD (Digital Versatile Disk) ROM, CD-R, CD-RW, HDD, and recorded in a removable disk, storage or can be or distribute. It is also possible to provide the above program through a network such as the Internet or electronic mail.

  DESCRIPTION OF SYMBOLS 100 ... Transmission side apparatus, 101 ... Transmission side control means, 200 ... Reception side apparatus, 201 ... Reception side control means, 300 ... Communication line.

Claims (9)

One frame of data is divided into blocks each having a predetermined data length and including a frame number indicating the numbered frame on the communication line and a block number indicating the numbered block in the frame. A communication system that performs communication via a communication line between a transmission-side device that transmits data and a reception-side device,
A transmission side control means provided in the transmission side device, and a reception side control means provided in the reception side device,
The transmission side control means includes
A function of transmitting the block;
A function of transmitting delivery confirmation data including the latest transmission frame number representing the latest transmission frame and the reception completion frame number representing the reception completion frame at the receiving side device after the block transmission;
When receiving reception state notification data including a frame number and a reception block state transmitted from the receiving side device, it has a function of transmitting an unreceived block designated by the data,
The receiving side control means includes:
A function of receiving a block transmitted from a transmission side device and assembling the received block into a frame;
When receiving acknowledgment data transmitted from the transmission side device, a reception state indicating which frame is not received based on the latest transmission frame number in the data and which block of the frame is not received A communication system having a function of transmitting notification data. The transmission side control means includes the newest transmission frame number and the reception completion frame number, and a new connection number generated from a random number at the time of initial connection to the communication line, and at the time of previous connection at the time of reconnection after line disconnection. A function of sending connection start notification data each assigned a connection number;
A function of transmitting the block after receiving the connection start notification data as a response from the receiving side device;
The receiving side control means includes:
A function for determining whether or not a number matching the connection number exists in the past communication record when connection start notification data is received from the transmission side device;
If the determination result is that there is a matching connection number, the reception completion frame number and the latest transmission frame number are taken over from the communication record. If the determination result is that there is no matching connection number, the new connection number is Features to add to
2. The communication system according to claim 1, further comprising a function of transmitting, as a response, notification data of the connection start after the communication record has been taken over or has been added.   3. The transmission side control means has a function of deleting reception completion frame data represented by a reception completion frame number in the delivery confirmation data from a transmission side memory. The communication system according to 1. The transmission side control means includes
A function for determining a length of the block as a first block length and performing communication for a predetermined period at an initial connection to the communication line;
A function of collecting communication anomalies within the predetermined period;
4. The function according to claim 1, further comprising: determining a length of the block as a second block length based on a frequency of occurrence of communication abnormality collected within the predetermined period. The communication system according to claim 1. One frame of data is divided into blocks each having a predetermined data length and including a frame number indicating the numbered frame on the communication line and a block number indicating the numbered block in the frame. A communication method in a communication system that performs communication via a communication line between a transmission-side device that transmits data and a reception-side device,
The transmission side control means of the transmission side device comprises:
Transmitting the block;
After the block transmission, transmitting delivery confirmation data including a latest transmission frame number representing the latest transmission frame and a reception completion frame number representing a reception completion frame at the receiving side device;
The receiving side control means of the receiving side device comprises:
Receiving a block transmitted from a transmission side device, and assembling the received block into a frame;
When receiving acknowledgment data transmitted from the transmission side device, a reception state indicating which frame is not received based on the latest transmission frame number in the data and which block of the frame is not received Sending notification data; and
The transmission-side control means includes a step of transmitting an unreceived block designated by the data when receiving the reception status notification data transmitted from the reception-side device. Communication method. The transmission side control means includes the newest transmission frame number including the latest transmission frame number and the reception completion frame number, and generated from a random number at the first connection to the communication line. Transmitting connection start notification data each assigned a connection number;
The receiving side control means is
Determining whether or not a number matching the connection number exists in the past communication record when connection start notification data is received from the transmission side device;
If the determination result is that there is a matching connection number, the reception completion frame number and the latest transmission frame number are taken over from the communication record. If the determination result is that there is no matching connection number, a new connection number is added to the communication record. Steps to add to
Transmitting the connection start notification data as a response after taking over or adding the communication record;
The communication method according to claim 5, further comprising: a step of transmitting the block after the transmission side control means receives the connection start notification data from the reception side device as a response.   7. The transmission side control means comprises a step of deleting reception completion frame data represented by a reception completion frame number in the delivery confirmation data from the transmission side memory. The communication method described in 1. The transmission side control means is
A step of determining a length of the block as a first block length and performing communication for a predetermined period at the time of initial connection to the communication line;
Collecting communication anomalies within the predetermined period;
8. The step of determining the length of the block as a second block length based on the frequency of occurrence of communication anomalies collected within the predetermined period. The communication method according to claim 1.   A communication program for causing a computer to function as each unit according to any one of claims 1 to 4.

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