JPH05103016A - Message transmission reception method - Google Patents

Abstract

PURPOSE:To provide the message transmission reception method in which a reception buffer is efficiently utilized and a message can be composed of a reception packet. CONSTITUTION:When a data block 19A of a head of each message is sent, information 17 representing a message length is added to a data packet, and a receiver side equipment secures a reception buffer whose capacity is equivalent to the message length information and composes a series of the reception packet into the message by utilizing the buffer. The message composition processing is surely implemented while not being in a deficient buffer capacity on the way of reception.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a message transmitting / receiving method, and more particularly to a message transmitting / receiving method of dividing a message into a plurality of data blocks and transmitting / receiving them as a plurality of data packets.

[0002]

2. Description of the Related Art Generally, a communication control device performs a communication protocol process by a communication control program including a transmission protocol processing unit and a reception protocol processing unit.

The transmission protocol processing unit transmits a message as a fixed-length packet. When the message to be transmitted is long, this message is divided into a plurality of data blocks and transmitted as a plurality of data packets. The header part of each data packet includes information indicating whether the end of the message is included. That is, for the packet including the end of the message, the EOT of the header part
"1" is set in the bit, and E is set in other packets.
"0" is set in the OT bit.

When a data packet is received, the reception protocol processing unit checks whether or not the message is divided into a plurality of data packets from the information contained in the data packet. That is, if the EOT bit of the header part included in the received data packet is set to 1, this data packet includes the end of the message, so the message is not divided and is transmitted as a single data packet. It is judged that it was done. On the other hand, if the EOT bit of the header part included in the received data packet is set to 0, it indicates that this data packet includes the beginning part of the message or the middle part thereof. Therefore, the message is assembled until the data packet in which the EOT bit of the header part is set to 1 (the data packet including the end of the message) is received.

Message assembly is executed by sequentially storing the data blocks included in the received data packet in the receive buffer. There are two conventional assembly processing methods. That is, first, as a first method, a short buffer having a size capable of storing a data block and a long buffer having a size capable of storing a maximum message are provided. If 0 is set in the EOT bit of the header at the time when a certain data packet is received, the data block is stored in an empty short buffer and the data packet in which 1 is set in the EOT bit is stored. Until the data is received, the data blocks are sequentially stored in this long buffer and the assembling process is performed.

As a second method, there is a method of providing a receiving buffer having a size capable of storing a data block included in one data packet and a buffer having a pointer for setting an address of another receiving buffer.

If a data block is set in the receive buffer and the EOT of this data packet is not 1,
Set the address of the receive buffer that stores the next data block in the receive buffer pointer. In this way, the data blocks are sequentially stored in the reception buffer, and the chain of the reception buffer is created and the assembling process is performed until the data blocks in the data packet in which the EOT bit is set to 1 are set in the reception buffer.

[0008]

However, the above-mentioned first problem
Method, regardless of the message length,
Since the receiving buffer that can store the maximum message is used, the receiving buffer is wasted. Further, when the second method is used, the receiving buffer is efficiently used, but the chain creating operation of the receiving buffer becomes a processing overhead when assembling a message, and the efficiency of the assembling processing is poor.

An object of the present invention is to provide a message transmission / reception method that can efficiently utilize a reception buffer and reduce the overhead of assembly processing.

[0010]

In order to achieve the above object, according to the present invention, the transmitting side sets information regarding the message length to be transmitted in the packet of the head data of each message, and the receiving side sets the information of each message. At the time of receiving the first data packet, a reception buffer necessary for message assembly is secured according to the message length information included in the reception data packet, and a series of subsequent reception data blocks is stored.

According to one embodiment of the present invention, the transmission side device divides a transmission message into a plurality of data blocks, adds predetermined header information to each data block, and transmits these as a data packet. For the transmission mode and the first data block of the transmitted message,
In addition to the header information, the second transmission mode in which information indicating the message length is added and transmitted is selected. The transmission side device transmits the first data packet to be transmitted after the connection is established in the second transmission mode,
Wait for a response from the receiving device. If the receiving device shows a normal response to the above data packet,
The transmitting device continues to transmit subsequent data packets in the second transmission mode. If there is no response from the receiving side device to the first data packet, the transmitting side device switches the transmission mode and transmits the first data block and the subsequent data blocks in the first transmission mode described above.

[0012]

According to the data transmitting / receiving method of the present invention, when the head data block of each message is transmitted, the information indicating the message length is added to the data packet. When the first packet is received, it is possible to know the capacity of the reception buffer required for assembling the message. Therefore, by securing a reception buffer with a capacity corresponding to the above message length information, a series of subsequent reception packets can be received without buffer shortage, and a message using the buffer memory effectively It can be assembled.

Further, in the case where the transmitting side device appropriately selects the first transmission mode and the second transmission mode, it is possible to transmit to a transmission partner which does not adopt the above-described method of preliminarily securing the reception buffer by the message length. However, since the communication can be performed as in the conventional case, the data transmission / reception method of the present invention can be put to practical use by being added to the existing network.

[0014]

[Embodiment 1] A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows a configuration example of a data communication system to which the present invention is applied. This system is composed of a plurality of computers 20 (20A, 20B, 20C), and each computer 20 has a communication control device 21 (21
A, 21B, 21C) via the network transmission line 2
Connected to 2. FIG. 3 is a detailed configuration diagram of the communication control device 21. The communication control device 21 is a device connected to a computer system bus 31 that connects the main processor 33 of the computer 20 and the main memory 30, and includes a local processor 34, a local memory 32, the local processor 34 and the local memory 32. A local bus 35 that connects the two, and a DMAC 36 used when transferring data
, A system bus control unit 37 connected to the computer system bus, a communication control circuit 38, and a bus arbiter for controlling the local bus 35. FIG. 4 shows a configuration example of a layered communication protocol applied by the main processor and the local processor of the communication control device 21 shown in FIG. From the lower layer, the physical layer L1, the MAC layer L2, and the LL
C layer L2 ', network layer L3, transport layer L
4, a session layer L5, a presentation layer L6, and an application layer L7. In this embodiment, the communication protocol processing executed by the communication control device 21 is the transport layer 40 or lower. ISO8073 class 4 (TP4) is implemented in the protocol of the transport layer 40.

FIG. 1 shows a data packet 19 (1
9A to 19C). The data packet 19 has an LI part 12 (header length): 1 byte, DT-I.
D part 13 (code indicating a DT packet): 1 byte, destination reference part 14: 2 bytes, EOT bit part 1
TP4 header section 18 composed of 5: 1 bit, TPDU-NR 16 section (sequence number): 7 bits
And a data block unit 11 (11A to 11C).

If the message 10 is divided into three pieces, divided data a, divided data b, and divided data c, and then transmitted, the data packet 19 (19A to 19C) has the data block 11A corresponding to the head portion of the message 10. First data packet 19A included and message 10
The second data packet 19B including the data block 11B corresponding to the central portion of the message and the last data packet 19C including the data block 11C corresponding to the tail portion of the message 10 are composed of three types. TP4 header 1
When creating 8, the EOT of the first data packet 19A
0 is set in the bit part 15A. The data block portion 11C of the last data packet 19C is the message 10
1 is set in the EOT bit portion 15B to indicate that the end of the EOT bit portion is included.

Further, the transmitting side sets information indicating the message length in the data packet 19A including the head portion of the message 10, and the receiving side sets the data packet 19A.
Upon reception, the reception buffer 53 is prepared based on the above message length information.

Specifically, the message 10 is divided into the maximum data length that can be transmitted, and the number of the above-mentioned data blocks is set in the data packet 19A including the head portion of the message 10. If the message 10 is divided into three, the first data packet 19A is composed of the TP4 header (EOT bit = 0) 18, the number 17 and the data block unit 11A, and the second and subsequent data packets 1
9B and 19C are composed of a TP4 header section 18 and data block sections 11B and 11C.

Further, the receiving side obtains the maximum message length of the message 10 to be received from the number 17 of the data blocks set in the data packet 19A including the head portion of the message 10, and the receiving buffer used when assembling the message. Find the size of 54. The maximum message length of the received message 10 is assumed to be the maximum data length (4 Kbytes in this embodiment) that can be set in the data portion of the data packet 19 which is determined when the TP4 connection is set. Calculate by formula.

(Maximum Message Length K Bytes) = (Number of Data Blocks) × (Maximum Data Length 4 K Bytes) Next, FIG. 5 is a diagram showing a transmission / reception process of a TP4 message processed by the local processor. The communication control program of TP4 processed by the local processor is TP
4 transmission processing units 51 (51A, 51B) and TP4 reception processing units 52 (52A, 52B) are provided to perform communication protocol processing.

In the TP4 transmission processing section 51A, TP4
When the message 10 for which the transmission request is received from the service user 50A is divided into three, from the buffer 53 in which the message 10 is set to another buffer 55 (55
The data block 11 (11A, 11B, 11C) obtained by dividing the message 10 into A, 55B, 55C) is copied, and the TP4 header 18 is added to the data block 11 by the communication protocol processing. TP4 reception processing unit 52
In B, the reception packet buffer 56 (56A, 56B,
Data block 11 (11A, 1) set to 56C)
1B, 11C) are sequentially set in the other buffers 54 used for assembling the message. When dividing or assembling a message in this way, the send buffer 5
It is necessary to prepare four types of buffers, namely, 3, a transmission packet buffer 55, a reception packet buffer 56, and a reception buffer 54. That is, the transmission message 10 is set in the transmission buffer 53 when a message transmission request is issued to the TP4 transmission processing unit 51 (51A, 51B). In the transmission packet buffer 55, the communication protocol in the TP4 transmission processing unit 51 is set. The data block 11 including the transmission data to which the processing is performed and the TP4 header 18 is added is set. In the reception packet buffer 56, the data packet received by the TP4 reception processing unit 52 is set. The reception packet buffer 54 includes the TP4 reception processing unit 5
The reception message 10 is set when the 2 reports the reception of the message to the TP4 service user. These 4
Among the types of buffers, the transmission buffer 53 and the reception buffer 54 for setting a message are arranged in the main memory 30, and the transmission packet buffer 55 and the reception packet buffer 56 are arranged in the local memory 32.

On the other hand, the receiving side selects the receiving buffer of the most suitable size from the receiving buffers having various kinds of sizes based on the information about the message length transmitted from the transmitting side. For example, the transferable message length is 6
If it is 4 Kbytes, six types of receive buffers 54 of 64 Kbytes, 48 Kbytes, 32 Kbytes, 16 Kbytes, 8 Kbytes, and 4 Kbytes are prepared. The size of the receive buffer 54 to be prepared varies depending on the purpose of use of the TP4 service user 50 and the like. The receive buffer length is set to the first 1 byte of the receive buffer 54. Each reception buffer 54 is managed by a reception buffer management table composed of an acquisition pointer, a release pointer, and a reception buffer setting part for each buffer length.

The acquisition method of the reception buffer 54 is to acquire the address of the reception buffer pointed by the acquisition pointer of the reception buffer management table corresponding to the acquired buffer length. The acquisition pointer is incremented by 4 bytes (corresponding to the address length of the reception buffer).

On the other hand, the method of releasing the receive buffer 54 is as follows: The address of the receive buffer to be released to the open receive buffer setting portion pointed to by the release pointer of the receive buffer management table corresponding to the buffer length set to the first byte of the receive buffer. By setting. Release pointer is 4
Increment by bytes (address length of receive buffer).

Next, a processing procedure for dividing a message will be described with reference to FIGS. 6 to 8.

FIG. 6 is a main routine showing the TP4 transmission process (100). The TP4 transmission processing unit 51
The requests received from the four service users 50 include a message transmission request, a connection setting request, and a connection release request. Upon receiving the request, the TP4 transmission process (100) first determines whether the request is a message transmission request (1
02), if it is a message transmission request, message transmission processing is executed (104).

FIG. 7 is a subroutine showing the message transmission process (104). Message transmission process (10
In 4), it is determined whether or not the transmission message length is larger than the maximum data length that can be transmitted as one data packet, 4 Kbytes (120).

If the transmission message length is smaller than or equal to 4 Kbytes, the transmission packet buffer 55 is acquired (124) and the transmission message 10 is set in the transmission packet buffer 55 (126). The TP4 header 18 is created and added to the transmission message 10 set in the transmission packet buffer 55. In this case, since the created data packet 19 includes the end of the transmission message, the EOT bit 15 of the TP4 header 18 is set to 1 (128).

If the transmitted message length is larger than 4 Kbytes, the message is divided (122).

FIG. 8 shows a process of dividing a message (12
It is a subroutine showing 2).

First, if the message 10 to be transmitted is divided by the maximum data length (4 Kbytes), the number of divisions required is calculated. If a 32 Kbyte message is to be transferred, the number of divisions n17 is "8".
(140).

Next, the transmission packet buffer 55 is acquired (142) and the data packet 19 is created.

When the first data packet 19A is created, 4 Kbytes from the beginning of the message 10 are set in the transmission packet buffer 55 (148). The number 17 is added to the beginning of the set data block 11A (15
0), TP4 header 18 (EOT bit = 0) is created and added (152).

When the second to the (n-1) th data packets 19B are created, the message 10 corresponding to the next part of the data block 11A transmitted immediately before is generated.
The data block 11B for 4 Kbytes is set in the transmission packet buffer 55 (154). In the set data block 11B, the TP4 header 18 (EOT bit =
0) is created and added (156).

When the nth data packet 19C is created, the data block 11C including the end of the message 10 is set in the transmission packet buffer 55 (14
4). A TP4 header 18 (EOT bit = 1) is created and added to the set data block 11C (14
6).

Next, the process of assembling the message is shown in FIG.
Starting from FIG. 12, description will be made.

FIG. 9 is a subroutine showing the TP4 reception process (160). The packets received by the TP4 reception processing unit 52 include an AK packet and a packet related to connection setting and release in addition to the data packet 19. First, when a packet is received, the type of the packet is determined (162), and if the packet is the data packet 19, message reception processing is executed (164). if,
If the packet is not the data packet 19, AK reception processing and connection setting / release processing (168) are performed.

FIG. 10 shows the message reception process (164).
Is a subroutine showing. First, the TP4 header 18
Is analyzed (180), and it is determined whether a message is being assembled in the connection that received the data packet 19 (182).

If the message is being assembled, the process of assembling the message is subsequently executed (194).

If the message is not being assembled, the EOT bit 1 contained in the received data packet 19
The processing is determined according to 5 (184). That is, if the EOT bit is not 1 (EOT bit = 0), a start process for assembling a message is performed (186).

When the EOT bit = 1, the message 10 is not divided because the data packet 19 includes the end of the message 10. Acquires a 4-Kbyte reception buffer 54 (188), stores the data of the received data packet 19 in the reception buffer 54 (190), and then reports the reception of the message to the TP4 service user 50 (192). ..

FIG. 11 is a subroutine showing the process (186) of assembling a message.

First, the maximum message length of the message 10 is obtained from the number 17 of data blocks set in the head portion of the head data block 11A by the method described above on the receiving side (200). Next, the reception buffer 54 matching the message length is acquired (202), and the data block 11A is stored in the reception buffer 54 (204). Furthermore, the data block 11 (11B,
11C) is continuously stored in the reception buffer 54, and an address obtained by adding the data block length to the start address of the reception buffer is set in the data setting pointer (20).
6).

Next, the data block 11 (11B, 11C) is set (2) at the position pointed to by this data setting pointer.
20) and increments the data setting pointer by the data block length (222).

Further, although the EOT bit 15 of the TP4 header 18 is judged (224), if the EOT bit = 0, it means that the message 10 has not been received until the end, so the message is continuously assembled. On the other hand, E
When OT bit is not 0 (when EOT bit is 1)
Indicates that the message 10 has been received to the end, and therefore reports the reception of the message to the TP4 service user 50 (226).

When the message 10 is divided and transmitted in this manner, the number of data blocks in the data packet 19A including the beginning of the message 10 is 1
By setting 7, the size of the message 10 to be transmitted is notified to the receiving side. On the other hand, the receiving side can previously assemble a message by selecting the receiving buffer 54 suitable for the size of the message 10 and storing the data block in this buffer.

[Second Embodiment] A second embodiment will be described with reference to FIGS. 12 to 15.

In this embodiment, the transport layer class 4 (TP4) to which the message sending / receiving method of the present invention is applied.
The transmission / reception processing unit not only enables communication using the message transmission / reception method of the present invention, but also enables communication with a standard transport layer class 4 (TP4) that does not notify the message length at the time of message transmission. It is a thing. That is, the transmission message is divided into a plurality of data blocks, each data block is added with predetermined header information to form a data packet, and the transmission message is divided into a plurality of data blocks, and each data block has a predetermined header. The transmitting side judges whether the mode is a mode in which the data packet is formed by adding the information and the message length, and the data packet is transmitted in the mode according to the judgment result. As the above determination method, after the transmission side establishes a connection with the reception side, the transmission side transmits the first message to the reception side, and the reception side according to the state of the response from the reception side Message transmission method is applied or standard TP4
You can determine whether is applied.

If the receiving side uses the standard TP4, the following method can be used. That is, the sending side changes to a method in which the message length is not notified when the message is sent, in accordance with the receiving side. This enables communication with the standard TP4 in the OSI protocol without releasing the transport connection.

The above-mentioned judgment is the sequence number of the data packet to be transmitted first after the TP4 connection setting is completed.
The maximum credit value is assigned as (hereinafter, referred to as TPDU-NR in this embodiment), and this value is exchanged with the sequence number of the AK packet for the first packet (hereinafter, referred to as TPDU-NR in this embodiment). Can be executed.

FIGS. 12 to 15 are sequence diagrams showing cases in which the transmitting side and the receiving side respectively apply and does not apply the message transmitting / receiving method of the present invention.

FIG. 12 is a sequence diagram when the message transmitting / receiving method of the present invention is applied to both the transmitting and receiving sides.

First, the transmitting side sets TPDU-NR of the first data packet including the information indicating the message length to 15 and transmits it (240).

On the receiving side, the T of the received data packet
Since the PDU-NR is not 0, it is determined that the transmitting side is applying the message transmitting / receiving method of the present invention (24
2), a value obtained by adding 1 to the AK packet (TPDU-NR =
16) is returned (244). On the other hand, on the transmitting side, since the TPDU-NR of the received AK packet is 16, the receiving side can also determine that the message transmitting / receiving method of the present invention is applied (246). After that, the data packet is continuously transmitted. However, in this data packet,
Information indicating the message length is not set.

FIG. 13 is a sequence diagram when only the receiving side applies the message transmitting / receiving method of the present invention.

First, since the transmission side is the standard TP4, the TPDU-NR of the first data packet to be transmitted is set to 0 and transmitted (248).

On the receiving side to which the message transmitting / receiving method of the present invention is applied, the TPDU- of the received data packet is
Since the NR is 0, it is determined that the transmission side is the standard TP4 (250).

Therefore, the receiving side uses the TP of the data packet.
Value obtained by adding 1 to DU-NR, that is, TPD of AK packet
The U-NR is set to 1 and returned (252).

FIG. 15 is a sequence diagram when only the transmitting side applies the message transmitting / receiving method of the present invention.

Since the transmitting side applies the message transmitting / receiving method of the present invention, the TPDU-NR of the data packet including the information indicating the message length to be transmitted first is 1
5 is set and transmitted (254).

On the other hand, since the receiving side is the standard TP4, it discards the data packet of TPDU-NR = 15 (256). Further, since the transmission of the data packet having TPDU-NR of 0 is requested, the TPD of the AK packet is transmitted.
U-NR is set to 0 and returned (258).

On the transmitting side, the TP of the received AK packet
Since DU-NR is 0, the receiving side uses standard TP4
(260).

Therefore, the data packet whose TPDU-NR is 0 is retransmitted (262). However, no information indicating the message length is set in this data packet.

FIG. 15 shows a sequence when the AK packet is not returned.

First, since the transmitting side applies the message transmitting / receiving method, the transmitting side sets TPDU-NR of the data packet including the information indicating the message length to be transmitted first to 15 and transmits it (264).

Even if the retransmission timer times out, A
If the K packet is not received, the data packets having the TPDU-NR of 15 are retransmitted one after another (266).

If the number of retransmissions is exceeded, TP
A data packet for which information indicating a message length in which DU-NR is set to 0 is not set is retransmitted (268).

On the other hand, when the transmitting side receives an AK packet with TPDU-NR set to 1, the receiving side receives the standard T packet.
It is determined to be P4 (270). If the AK packet is not received even if the retransmission timer times out, T
Release P4 connection.

As described above, by judging whether or not the transmission partner applies the present invention, the communication by the message transmitting / receiving method of the present invention can be performed without disconnecting the TP4 connection, and the protocol of the OSI protocol can be used. Communication with the standard transport layer class 4 is also possible.

[0070]

As is apparent from the above description, according to the present invention, when the receiving side receives the first data packet of each message sent from the transmitting side, the message included in the prior application data packet is received. Since a receive buffer is prepared according to the length information and data blocks are stored in this buffer one after another, there is no risk of running out of the receive buffer during the reception of each message, and the buffer memory for reception can be used efficiently. You can assemble a message while making good use of it.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a data packet format when a message is divided.

FIG. 2 is a diagram showing a configuration example of a data communication system according to the present invention.

FIG. 3 is a configuration diagram of a communication control device in the embodiment.

FIG. 4 is a diagram illustrating a communication protocol configuration example in a communication control device.

FIG. 5 is a diagram showing a message transmission / reception process.

FIG. 6 is a main routine showing a TP4 transmission process.

FIG. 7 is a subroutine showing a message transmission process.

FIG. 8 is a subroutine showing a process for dividing a message.

FIG. 9 is a subroutine showing a TP4 reception process.

FIG. 10 is a subroutine showing a message receiving process.

FIG. 11 is a subroutine showing a message assembly start process.

FIG. 12 is a sequence diagram when the message transmitting / receiving method is applied to both the transmitting and receiving sides.

FIG. 13 is a sequence diagram when only the receiving side applies the message transmitting / receiving method.

FIG. 14 is a sequence diagram when only the transmitting side applies the message transmitting / receiving method.

FIG. 15 is a sequence diagram when an AK packet is not returned.

[Explanation of symbols]

10 ... Message to be transmitted / received, 11 ... Data block obtained by dividing message, 15 ... EOT bit of TP4 header, 17 ... Number of data blocks, 18 ...
TP4 header, 19 ... TP4 data packet, 20 ... computer, 21 ... communication control device, 30 ... main memory, 32 ... local memory, 40 ... transport class 4 (TP
4), 50 ... TP4 service user, 51 ... TP4 transmission processing unit, 52 ... TP4 reception processing unit, 53 ... Transmission buffer, 54 ... Reception buffer, 55 ... Transmission packet buffer, 56 ... Reception packet buffer, 100 ... TP4 transmission Processing, 104 ... Message transmission processing, 122 ... Message division processing, 160 ... TP4 reception processing, 164 ... Message reception processing, 186 ... Message assembly processing.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location 8020-5K H04L 13/00 307 Z (72) Inventor Matsuaki Terada 1099 Ozenji, Aso-ku, Kawasaki-shi, Kanagawa Bachi Co., Ltd. Hitachi, Ltd. System Development Laboratory

Claims (6)

[Claims] 1. A transmission side device divides one message into a plurality of data blocks, packetizes each data block, and sequentially transmits the data blocks. A reception side device extracts a plurality of data blocks from a plurality of reception packets. In the message transmission / reception method of assembling into one original message, the transmission side device adds message length information indicating the length of the above message or the number of packets to the packet (start packet) including the first data block of each message. The reception side device prepares a reception buffer having a storage capacity according to the message length information included in each packet, every time the reception side device receives the top packet of each message, and the data extracted from the top packet is set. block,
And a method of transmitting and receiving a message, wherein the data blocks extracted from subsequent packets of the same message are sequentially stored in the reception buffer to assemble the message. 2. The message transmitting / receiving method according to claim 1, wherein the transmitting side device transmits, as the message length information, information indicating the number of the data blocks. 3. The reception side device stores a plurality of types of reception buffer capacities, and each time a head data packet of a message is received, the reception type of the plurality of types is received according to message length information included in the data packet. The message transmitting / receiving method according to claim 1 or 2, wherein one of the buffer capacities is selected and a reception buffer having the selected capacity is prepared. 4. A first transmission mode for dividing a transmission message into a plurality of data blocks, adding predetermined header information to each data block, and transmitting the data block as a data packet.
The transmission message is divided into a plurality of data blocks, predetermined header information is added to each data block, and information indicating the message length is further added to the first data block of the transmission message. A transmission mode, and after establishing a connection with the partner device, the first message is transmitted in the second transmission mode, and depending on the state of the response from the partner device, the second transmission mode is set. A method for transmitting a message, characterized by determining whether to continue the transmission or to retransmit the first message in the first transmission mode. 5. The transmission side device gives no response to the header part of the first packet including the first message, if the partner device is a device operating in the first transmission mode, no response, second
A method of transmitting and receiving a message, characterized in that identification information is set so that a response packet is returned if the device operates in the transmission mode. 6. The transmission side device, as the identification information,
The message transmitting / receiving method according to claim 5, wherein a packet sequence number within a specific range is used.