JP2004088697A - Network communication system between computers - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform communications among a plurality of PLC and further to guarantee transmissions by broadcast communications to be performed by a UDP protocol. <P>SOLUTION: In each of PLC 1A-1N, a processor 3 is provided with a user memory 31 and an application program 32, and an Ethernet(R) interface 2 is provided with a physical layer 21, a data link layer 22, an IP 23, a UDP 24 and a data transmitting-receiving function part 25. In the case of broadcast transmission by UDP, the transmitting side PLC designates only one delivery confirmation reply station and obtains delivery confirmation from the designated station to guarantee sure sending of data. When the delivery confirmation from the designated station is not reported even after the lapse of fixed time, resending is performed while designating a station different from that of the first transmission as a delivery confirmation reply station. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a network communication method between computers, such as PLCs (Programmable Logic Controllers), which connect computers to each other via Ethernet (registered trademark) to perform communication with each other.
[0002]
[Prior art]
This type of communication system is disclosed in, for example, JP-A-2001-245014. The communication method based on TCP / IP is described in detail in the document "SOFTBANKBOOKS, TCP / IP, W. Richard Stevens, translator Yasuo Tachibana".
[0003]
As disclosed in the above-mentioned publications and documents, Ethernet uses a coaxial cable as a data transmission medium, and enables communication between computers through a CSMA / CD system (collision detection type carrier wave multiplex LAN access system) interface. .
[0004]
In recent years, monitoring and control systems in plants have adopted personal computers in place of workstations and minicomputers as host computers, and with this, the most common Ethernet has been established as the de facto standard for computer host networks and inter-computer networks. Good.
[0005]
When implementing the TCP / IP protocol in an interface for communication using Ethernet, these personal computers and PLCs use TCP / IP having the concept of a logical line if reliability is important.
[0006]
If the user does not like the connection and disconnection processing of the logical line, one-to-one communication is realized by UDP / IP. Note that UDP is a protocol that does not itself have a retransmission process and does not perform delivery confirmation.
[0007]
[Problems to be solved by the invention]
TCP / IP is highly reliable communication, but has the disadvantage that one-to-N communication is not possible.
[0008]
UDP / IP is capable of broadcast communication, but has the disadvantage that the protocol itself does not have a retransmission function or a delivery confirmation function.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a network communication method that can efficiently and reliably guarantee transmission by broadcast communication performed by a UDP protocol for communication between computers connected to a network via Ethernet.
[0010]
[Means for Solving the Problems]
According to the present invention, the transmitting station specifies a delivery confirmation reply station for only one station when performing broadcast transmission by UDP, and obtains a delivery confirmation from the designated station, thereby guaranteeing that data has been transmitted reliably. Accordingly, the communication efficiency is improved as compared to receiving delivery confirmation from a plurality of stations.
[0011]
In addition, if the delivery confirmation from the designated station is not notified even after a certain period of time has elapsed, the transmitting station specifies a station different from the time of the first transmission as the delivery confirmation reply station and retransmits the delivery confirmation reply station. It is designed to suppress unnecessary retransmissions when down, and features the following communication methods.
[0012]
(1) The plurality of computers each include a processor on which a user memory and an application program are mounted, and an Ethernet interface having a physical layer, a data link layer, an IP, a UDP, and a data transmission / reception function unit provided at a connection unit of the processor. And a communication method for performing network communication between the computers,
The sending computer
Means for specifying a delivery confirmation reply station limited to one station when broadcasting by UDP and obtaining a delivery confirmation from the designated station, thereby assuring that data has been transmitted reliably;
When the acknowledgment from the designated station is not notified even after the elapse of a predetermined time, there is provided a means for designating a station different from the time of the first transmission as the acknowledgment return station and performing retransmission.
[0013]
(2) The data format broadcast-transmitted by the transmission-side computer includes an IP address of its own station set as the source station IP address, a delivery confirmation reply designated station IP address set with the IP address of a station that returns the delivery confirmation, and It consists of broadcast data used by the application program of the receiving station,
The data format transmitted by the delivery confirmation response designated station that has received the broadcast transmission includes a transmission source IP address for setting its own IP address and a transmission confirmation reply destination IP for setting the IP address of the broadcast transmission station. And an address.
[0014]
(3) The transmission start processing of the transmission-side computer includes:
When a broadcast transmission event occurs in the application program, a retransmission counter prepared on the user memory is initialized, a broadcast transmission buffer for broadcast transmission is created, and a delivery confirmation reception wait timer is started. Finally, a transmission request is issued to the Ethernet interface.
[0015]
(4) The sending computer waits for a delivery confirmation.
After the broadcast is transmitted by the application program, the process ends if the acknowledgment reception waiting timer times out, otherwise waits for the acknowledgment reception, and stops the acknowledgment reception waiting timer when the acknowledgment is received Then, the broadcast transmission process is completed.
[0016]
(5) The time-up processing of the acknowledgment reception waiting timer includes:
After the broadcast transmission by the application program, if the retransmission counter is the maximum number of retransmissions, a transmission failure process is performed, and if the retransmission counter is less than the maximum number of retransmissions, the retransmission counter is incremented by one, and It is characterized in that the IP address of another station is reset and a transmission request is issued to the Ethernet interface.
[0017]
(6) The broadcast receiving process includes:
When receiving the broadcast transmission data, the application data portion is fetched into the user memory, and thereafter, it is checked whether the delivery confirmation reply designated station IP address of the application header matches the own station IP address, If not, the process is terminated, and if they match, a delivery confirmation transmission buffer is created and a transmission request is issued to the Ethernet interface.
[0018]
(7) The transmission request processing of the data transmission / reception function unit includes:
When the application program receives a transmission request from the processor by issuing a transmission request, the first word of transmission data is checked, and if the data indicates a broadcast identifier, the destination IP address is set to a broadcast address and transmitted to the UDP. A request is issued, and if the data indicates a delivery confirmation identifier, a transmission request is issued to the UDP using the destination IP address as the delivery confirmation return destination IP address in the buffer.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
In the system configuration according to the embodiment of the present invention, as shown in FIG. 1, a PLC 1A and PLCs 1B to 1N are connected by Ethernet. Note that the same applies to the case where these are used as computers.
[0020]
Each of the PLCs 1A, 1B to 1N is provided with an Ethernet interface 2 for obtaining an intercommunication function, as represented by the PLC 1A. The processor 3 has a user memory 31 and an application program (application layer) 32 that uses it.
[0021]
The Ethernet interface 2 is provided with a data transmission / reception function unit 25 at a coupling unit with the processor 3 in addition to the physical layer 21, the data link layer 22, the IP 23 and the UDP 24. The data transmission / reception function unit 25 is configured by software like the data link layer 22, the IP 23, and the UDP 24.
[0022]
In the above configuration, the main parts are the user memory 31 and the application program 32 of the processor 3 and the data transmission / reception function unit 25 of the Ethernet interface 2. The data transmission / reception function unit 25 is used for broadcast (broadcast) communication which is a feature of UDP. Achieve reliable communication without loss.
[0023]
2A and 2B show a basic broadcast transmission process. FIG. 2A shows a case where a delivery confirmation reply designated station at the first transmission is normal, and FIG. 2B shows a delivery confirmation at the first transmission. Indicates that the designated reply station is abnormal.
[0024]
As shown in FIG. 2A, the PLC 1A serving as the broadcast transmitting station obtains a delivery confirmation from the PLC 1B serving as the delivery confirmation reply designating station in response to the UDP / IP broadcast transmission, so that the data is reliably transmitted. Take assurance that The feature here is that the station that returns the acknowledgment is limited to one station specified by the transmitting station, and it is not necessary to receive the acknowledgment of the transmission of the data from a plurality of stations.
[0025]
In addition, as shown in FIG. 2B, if the transmission confirmation is not received even after the elapse of a predetermined time, the transmitting station performs retransmission. The feature at that time is that the acknowledgment / reply station designated by the transmitting station is a station (PLC1C in the figure) different from that at the time of the first transmission. By doing so, it is possible to suppress unnecessary retransmission when the delivery confirmation reply station goes down.
[0026]
A data format and each processing for realizing the above communication processing will be described in detail below.
[0027]
(A) Data Format of Broadcast Transmission Buffer FIG. 3 shows a format of a transmission data buffer created on the user memory 31 by the application program 32 of the PLC that performs broadcast (broadcast) transmission. The UDP header, the IP header, and the Ethernet header are added by the Ethernet interface 2.
[0028]
In FIG.
(1) The broadcast identifier is data indicating broadcast transmission, and may be any value.
[0029]
(2) The source station IP address sets the IP address of the own station.
[0030]
(3) The delivery confirmation reply designated station IP address sets the IP address of the station that returns the delivery confirmation.
[0031]
(4) The broadcast data is application data used by the application program of the receiving station.
[0032]
(B) Data Format of Delivery Confirmation Transmission Buffer FIG. 4 shows that the application program 32 of the PLC that has received the broadcast transmission (determined by the broadcast identifier of the received data) has its own station designated as the delivery confirmation reply designated station. 3 shows a format of a delivery confirmation transmission buffer created on the data memory 31. The UDP header, the IP header, and the Ethernet header are added by the Ethernet interface 2.
[0033]
In FIG.
(1) The delivery acknowledgment identifier is data indicating delivery acknowledgment to broadcast transmission, and may be any value.
[0034]
(2) The source station IP address sets the IP address of the own station.
[0035]
(3) As the delivery confirmation reply destination IP address, the IP address of the station that has transmitted the broadcast is set.
[0036]
(C) Transmission start processing of the transmitting station FIG. 5 shows an algorithm of the transmission start processing in the application program 32 of the broadcast transmitting station.
[0037]
In the figure, when a broadcast transmission event occurs in the application program of the PLC (A1), first, a retransmission counter prepared on the user memory is set to 0 (initialized) (A2). Next, a broadcast transmission buffer is created for broadcast transmission (A3). At this time, an arbitrary station existing on the same transmission path is set as the delivery confirmation reply designated station in the application header. Further, the acknowledgment reception waiting timer is started with an arbitrary value (A4). Finally, a transmission request is issued to the Ethernet interface 2 (A5).
[0038]
(D) Transmission Confirmation Waiting Process of Transmitting Station FIG. 6 shows an algorithm of a delivery confirmation waiting process in the application program 32 of the broadcast transmitting station.
[0039]
In the figure, after the broadcast is transmitted by the application program of the PLC, if the acknowledgment reception waiting timer times out, the processing is terminated, and the process proceeds to the acknowledgment reception waiting timer time-up processing. If the time is not up, it waits for reception of the delivery confirmation (B1). When the delivery confirmation is received (B2), the delivery confirmation reception waiting timer is stopped, and the broadcast transmission processing is completed (B3).
[0040]
(E) Time-Up Processing of Delivery Confirmation Receiving Wait Timer FIG. 7 shows an algorithm of time-up processing when the delivery confirmation reception waiting timer times out after broadcast transmission by the application program of the PLC.
[0041]
In the figure, if the retransmission counter is N (N = maximum number of retransmissions) (C1), it means that a predetermined number of retransmissions have been completed, so a transmission failure process is performed (C4), and the process ends.
[0042]
If the retransmission counter is less than N, it means that retransmission is in progress, the retransmission counter is incremented by 1 (C2), the IP address of another station is set again as the delivery confirmation reply designated station IP address of the application header (C4), and the Ethernet interface A transmission request is issued to C2 (C5).
[0043]
(F) Broadcast Reception Processing FIG. 8 shows a broadcast reception processing algorithm of the application program 32 of the PLC that has received the broadcast transmission data.
[0044]
In the figure, when the broadcast transmission data is received (recognized by the broadcast identifier of the application header) (D1), the application data portion is loaded into the user memory 31 (D2).
[0045]
Thereafter, it is checked whether the delivery confirmation reply designated station IP address in the application header matches the own station IP address (D3), and if not, the process is terminated. If they match, a transmission confirmation transmission buffer is created (D4), and a transmission request is issued to the Ethernet interface 2 (D5).
[0046]
(G) Transmission Request Processing of Data Transmission / Reception Function FIG. 9 shows an algorithm when the data transmission / reception function unit 25 of the Ethernet interface 2 receives a transmission request from the processor 3.
[0047]
In the figure, when the application program 32 issues a transmission request and receives a transmission request from the processor (E1), the first word of the transmission data is checked, and if the data indicates a broadcast identifier (E2), the destination IP A transmission request is issued to the UDP using the address as a broadcast address (E3).
[0048]
If the data indicates the delivery confirmation identifier (E4), the transmission request is issued to the UDP with the destination IP address as the delivery confirmation return destination IP address in the buffer (E5).
[0049]
【The invention's effect】
As described above, according to the present invention, the transmission station specifies the acknowledgment return station only to one station when performing broadcast transmission by UDP, and the transmission acknowledgment is obtained from the designated station so that the data is reliably transmitted. Communication efficiency can be improved as compared to receiving delivery confirmation from a plurality of stations.
[0050]
In addition, if the acknowledgment from the designated station is not notified even after a certain period of time, the transmitting station specifies the station different from the first transmission as the acknowledgment station and performs retransmission. It is possible to suppress unnecessary retransmission when the station goes down.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing an embodiment of the present invention.
FIG. 2 is a diagram illustrating a broadcast transmission path using UDP in the present invention.
FIG. 3 is a data format of a broadcast transmission buffer in the embodiment.
FIG. 4 is a data format of a delivery confirmation transmission buffer in the embodiment.
FIG. 5 is a transmission start process of the transmitting station in the embodiment.
FIG. 6 is a transmission confirmation waiting process of the transmitting station in the embodiment.
FIG. 7 shows a delivery confirmation reception waiting process in the embodiment.
FIG. 8 illustrates a broadcast reception process according to the embodiment.
FIG. 9 illustrates a transmission request process of the data transmission / reception function unit according to the embodiment.
[Explanation of symbols]
1A, 1B, 1N ... PLC
2 Ethernet interface 3 Processor 21 Physical layer 22 Data link layer 23 IP
24 ... UDP
25 data transmission / reception function 31 user memory 32 application program

Claims (7)

The plurality of computers each include a processor on which a user memory and an application program are mounted, and an Ethernet (registered trademark) interface having a physical layer, a data link layer, an IP, a UDP, and a data transmission / reception function unit at a connection unit of the processor. A communication method for network communication between each computer,
The sending computer
Means for specifying a delivery confirmation reply station limited to one station when broadcasting by UDP and obtaining a delivery confirmation from the designated station, thereby assuring that data has been transmitted reliably;
A means for designating a station different from the time of the first transmission as a delivery confirmation reply station and retransmitting when the delivery confirmation from the designated station is not notified even after a lapse of a predetermined time. Network communication method. The data format transmitted by the transmitting computer in broadcast transmission includes an IP address of its own station and an IP address of a transmitting station, an IP address of a acknowledgment return designated station in which an IP address of an acknowledgment station is set, and an IP address of a receiving station. It consists of broadcast data used by application programs,
The data format transmitted by the delivery confirmation response designated station that has received the broadcast transmission includes a transmission source IP address for setting its own IP address and a transmission confirmation reply destination IP for setting the IP address of the broadcast transmission station. 2. The network communication method between computers according to claim 1, wherein the network communication method comprises an address. The transmission start process of the transmission-side computer,
When a broadcast transmission event occurs in the application program, a retransmission counter prepared on the user memory is initialized, a broadcast transmission buffer for broadcast transmission is created, and a delivery confirmation reception wait timer is started. 3. The computer-to-computer network communication method according to claim 1, wherein a transmission request is issued to the Ethernet interface last. The delivery confirmation waiting process of the sending computer,
After the broadcast is transmitted by the application program, the process ends if the acknowledgment reception waiting timer times out, otherwise waits for the acknowledgment reception, and stops the acknowledgment reception waiting timer when the acknowledgment is received The network communication method between computers according to any one of claims 1 to 3, wherein the broadcast transmission processing is completed. Time-up processing of the delivery confirmation reception waiting timer,
After the broadcast transmission by the application program, if the retransmission counter is the maximum number of retransmissions, a transmission failure process is performed, and if the retransmission counter is less than the maximum number of retransmissions, the retransmission counter is incremented by one, and 5. The network communication method between computers according to claim 1, wherein an IP address of another station is reset, and a transmission request is issued to the Ethernet interface. The broadcast receiving process,
When receiving the broadcast transmission data, the application data portion is fetched into the user memory, and thereafter, it is checked whether the delivery confirmation reply designated station IP address of the application header matches the own station IP address, The computer according to any one of claims 1 to 5, wherein the processing is terminated if not, and if they match, a delivery confirmation transmission buffer is created and a transmission request is issued to the Ethernet interface. Network communication method. The transmission request processing of the data transmission / reception function unit includes:
When the application program receives a transmission request from the processor by issuing a transmission request, the first word of transmission data is checked, and if the data indicates a broadcast identifier, the destination IP address is set to a broadcast address and transmitted to the UDP. 7. A request is issued, and if the data indicates a delivery confirmation identifier, a transmission request is issued to the UDP by setting a destination IP address to a delivery confirmation return destination IP address in a buffer. 2. A network communication method between computers according to claim 1.

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