JPH10173676A - Communication device - Google Patents

Abstract

(57) [Summary] [Problem] It is difficult to identify a faulty part of a LAN. SOLUTION: A monitoring device 1 and monitored devices 2a to 2c are provided.
, Includes message transmission devices 3, 3a to 3c, message reception devices 4, 4a to 4c, and failure determination devices 5, 5a to 5c, and two communication paths 6 from the message transmission device 3 of the monitoring device 1.
Confirmation messages are transmitted to the monitored devices 2a to 2c via the communication devices 6a and 6b, and based on response messages returned from the monitored devices 2a to 2c to the monitoring device 1 via the two communication paths 6a and 6b. The fault determination device 5 of the monitoring device determines fault locations of the two communication paths 6a and 6b and the plurality of monitored devices 2a to 2c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a TCP / IP [Tra] for managing information such as plant control.
nsmission Control Protocol
1 / Internet Protocol (Transmission Control Protocol / Internet Protocol)], and a communication device that detects an abnormality in a communication path and automatically avoids the abnormality.

[0002]

2. Description of the Related Art FIG. 12 is a block diagram showing a conventional communication device using polling. In FIG. 12, reference numeral 50 denotes a monitoring device, 51 and 52 denote monitored devices, and 53 and 54 denote LANs.
Two communication paths 55 to 60 constituted by (local area network) are transceivers for connecting the monitoring apparatus 50, the monitored apparatuses 51 and 52 and the two communication paths 53 and 54.

Next, the operation will be described. Monitoring device 50
Performs broadcast transmission to the two communication paths 53 and 54 at regular intervals, and monitors responses from the monitored devices 51 and 52 through the communication paths 53 and 54. If there is no response from the communication path 53 within a predetermined time, it is determined that the communication path 53 is abnormal, and the communication path 53 is manually or automatically switched to the communication path 54.

[0004] For example, as shown in FIG.
It is assumed that a failure has occurred in the transceiver 59 which is a contact point with the communication path 53 of FIG. The monitoring device 50 detects that a failure has occurred in the communication path 53 due to the interruption of the communication from the monitored device 52 via the communication path 53, disconnects the communication path 53, and disconnects the communication path 54. Make the connection. The monitored devices 51 and 52 also connect to the communication path 54 with the same settings, and the communication software program on each computer resumes communication via the communication path 54 by reestablishing the connection.

[0005]

Since the conventional communication apparatus is configured as described above, when a failure occurs, the connection of the program that has been executed up to that point is temporarily disconnected and the connection is newly reconnected. Processing was required, and software had to be modified to accommodate the switch. Also,
When switching from the communication path 53 to the communication path 54 due to the LAN failure of the monitored device 51, there is a problem in that the communication program between the monitoring device 50 and the monitored device 52 that is not directly related to the failure ends. Further, the failure state is centrally managed by the monitoring device 50. Therefore, computers other than the monitoring device 50 simply return a response,
There is no information on the state of each communication path 53, 54. For this reason, there is a problem that it is difficult to specify a trouble site of the LAN.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to obtain a communication device capable of specifying a failure site. In addition, the present invention
It is an object of the present invention to provide a communication device capable of switching only a path in which communication is disabled due to a failure without stopping a communication program being executed.

[0007]

According to a first aspect of the present invention, a communication device transmits a confirmation message from a monitoring device to a plurality of monitored devices via two communication paths and receives the confirmation message. Accordingly, based on the response messages returned from the plurality of monitored devices via the two communication paths, the failure points of the two communication paths and the plurality of monitored devices are determined.

According to a second aspect of the present invention, there is provided a communication device comprising: a monitoring device and a plurality of monitored devices;
The monitoring device includes a message receiving device and a failure determination device,
A confirmation message is transmitted from the message transmission device of the monitoring device to the message reception devices of the plurality of monitored devices via the two communication paths, and in response to the reception of the confirmation message of the message reception device of the plurality of monitored devices. 2 from message transmission devices of a plurality of monitored devices
Based on the response message returned to the message receiving device of the monitoring device via the communication path of the book, the fault determining device of the monitoring device determines two communication paths and the failure points of the plurality of monitored devices, and confirms the confirmation message. The fault location is transmitted to the plurality of monitored devices.

According to the third aspect of the present invention, the communication device of the monitored device receives no confirmation message from the monitored device via the two communication paths in the message receiving device of the monitored device. A confirmation message is transmitted from the message transmission device to the message reception device of the other monitored device via the two communication paths, and another monitored message is received in response to the reception of the confirmation message of the message reception device of the other monitored device. Based on the response message returned from the message transmission device of the device to the message reception device of the monitored device via the two communication paths, the failure determination device of the monitored device causes a failure of the monitoring device or two communication path failures. Is determined.

[0010] In the communication device according to the fourth aspect of the present invention, when the failure determination device of the monitoring device determines that the communication path currently being communicated has a failure, the communication is disabled by the communication path having the failure. In addition to disabling the communication destination item in the routing table, the data being communicated is temporarily stored in the monitoring device or monitored device on the transmission side, and the communication route corresponding to the disabled item in the routing table is determined. Transmission of data to the monitoring device or the monitored device via the network device, and enabling the disabled monitoring device name or monitored device name and the item of the normal communication route in the route table, The data once stored in the monitoring device on the transmission side or the monitored device, or the monitoring device of the communication destination via the normal communication path corresponding to the newly enabled item in the routing table or Those having a specific communication path switching apparatus to be transmitted to the monitoring device.

In the communication apparatus according to the present invention, all the items of the communication destination monitoring device name or monitored device name and the communication path are registered in the path table in advance, and are enabled or disabled by the specific communication path switching device. Is set to.

According to a sixth aspect of the present invention, there is provided a communication device wherein a monitoring device can be dynamically switched to a monitored device and a monitored device can be dynamically switched to a monitoring device.

The communication device according to the present invention is provided with a priority setting table in which the priorities of the monitoring devices are set in advance, and the dynamic switching from the monitored device to the monitoring device is performed by:
This is performed according to the priority set in the priority setting table.

The communication device according to the invention of claim 8 is such that the monitored device which first determines the failure of the monitoring device is dynamically switched from the monitored device to the monitoring device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a block diagram showing a communication device according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes a monitoring device, 2a to 2c denote monitored devices, and message transmission devices 3, 3a to 3c, and Receiving devices 4, 4a to 4
c and failure determination devices 5, 5a to 5c. 6
a and 6b are two communication paths configured by LAN,
7a, 7b, 7aa, 7ab, 7ba, 7bb, 7c
Reference numerals a and 7cb denote transceivers that connect the monitoring device 1, the monitored devices 2a to 2c, and the two communication paths 6a and 6b. As shown in FIG. 2, reference numeral 10 denotes a confirmation message table, which includes columns for a communication path 11, a host name (or network address) 12, a path state 13, and a response message transmission time 14.

Next, the operation will be described. FIG. 3 is a flowchart showing the operation of the monitoring device. FIG. 3A shows the operation of the message transmitting device of the monitoring device, and FIG. 3B shows the operation of the message receiving device of the monitoring device. FIG.
Is a flowchart showing the operation of the monitored device. FIG.
As shown in (a), the monitored devices 2a to 2 are transmitted from the message transmission device 3 of the monitoring device 1 via two communication paths 6a and 6b.
Confirmation message is transmitted to c at regular intervals (step S
T11), and wait for a certain time (step ST12). Here, as the confirmation message transmitted from the monitoring device 1 to the monitored devices 2a to 2c, data corresponding to the confirmation message table is transmitted as shown in FIG. Further, the monitored devices 2a to
The contents of the confirmation message table are changed according to the response message received from 2c via the two communication paths 6a and 6b (step ST13). From the monitoring device 1 to the monitored device 2a
2c is transmitted based on the confirmation message table shown in FIG. That is, the host name 12 is host1
In the (monitoring device 1), since the path state 13 of the host 1 is set to be monitored, the host 1 is used as a monitoring device, and the other hosts 2 to 4 are used as monitored devices. When the response message is returned, it is determined that the communication path is normal, and the path state 13 is set to “○”. On the other hand, when the response message is not returned within a predetermined time, a failure occurs in the communication path. It is determined that an error has occurred, and the route state 13 is set to “×”. Further, the time stamped when the response message is transmitted from the monitored devices 2a to 2c is set as the response message transmission time 14.

As shown in FIG. 3B, the message receiving device 4 of the monitoring device 1 checks the reception of a response message for each of the two communication paths 6a and 6b (step ST21), When the response message from the monitored devices 2a to 2c arrives (step ST22), the contents of the confirmation message table are changed, and the process returns to step ST21. The response message received by the message receiving device 4 is sent to the failure determination device 5.
On the other hand, if the response messages from all the monitored devices 2a to 2c have not arrived, the process waits for a certain period of time (step ST23).
If the response message does not arrive even after a certain period of time has elapsed, it is determined that a failure has occurred in the communication path of the monitored device to which the response message has not reached, and the failure determination device 5 is notified of the failure.
Return to 21.

Further, as shown in FIG.
The message receiving devices 4a to 4c a to 2c investigate the reception of the confirmation message transmitted at a fixed period via the two communication paths 6a and 6b (step ST31), and transmit the confirmation message to the message receiving devices 4a to 4c. 4c, the message transmission device 3a
3c return a response message (step ST32).

Here, the operation when a failure occurs will be described. As shown in FIG. 1, when a failure occurs on the cable connecting the monitored device 2b and the transceiver 7ba and communication becomes impossible, the monitoring device 1 connects the monitored device 2b to the communication path 6a. No response message was received via
In addition, since a response message is received from the other monitored devices 2a and 2c, it is detected that a failure has occurred on the cable of the monitored device 2b. The failure determination device 5 updates the corresponding route state 13 in the confirmation message table to “x” indicating that the monitored device 2b cannot communicate (step ST).
13). The monitored device 2b determines from the failure determination device 5b that the confirmation message from the communication path 6a has been interrupted and that a failure has occurred on the communication path 6a from the contents of the confirmation message received from the communication path 6b. Is done.

In the monitored device, the communication path 6a
When both the confirmation message from the communication path 6b is lost, the failure determination device of the monitored device performs communication with another monitored device. First, a confirmation message is transmitted from the message transmission device of the monitored device whose both confirmation messages have been interrupted to another monitored device, the confirmation message is received from the message reception device of the other monitored device, and the confirmation message is transmitted. The response message is returned from the message transmission device of the other monitored device to the monitored device for which both of the confirmation messages have been interrupted. In the monitored device in which both of the confirmation messages have been interrupted, if the failure determination device receives a response message from the message receiving device, it determines that the computer of the monitoring device 1 has stopped, and receives the response message. If not, it is determined that a failure has occurred in the two communication paths 6a and 6b.

As described above, according to the first embodiment, a confirmation message and a response message are transmitted and received between the monitoring device 1 and the monitored devices 2a to 2c, whereby the two communication paths 6a, 6b, Monitored devices 2a to 2c
In addition, it is possible to identify the location where the failure of the monitoring device 1 has occurred, and it is possible to realize a quick recovery measure for the failure location. Further, there is an effect that the occurrence time of the failure can be specified from the confirmation message table 10.

Embodiment 2 FIG. FIG. 5 is a block diagram showing a communication apparatus according to a second embodiment of the present invention. In the figure, reference numerals 15, 15a and 15b denote specific communication path switching apparatuses provided in the monitoring apparatus 1 and the monitored apparatuses 2a and 2b. The specific communication path switching devices 15, 15a, 15b
When it is determined that there is a failure in the communication paths 6a and 6b,
The route table as shown in FIG. 6 is updated so that communication can be performed via a normal communication route. FIG.
FIG. 4 is an explanatory diagram showing a route table in which information on communication destination routes of data on the monitoring device and the monitored device is registered. This routing table 20 is provided in the monitoring device 1 and the monitored devices 2a and 2b. This is referred to when implementing TCP communication. In the figure, 21 is a communication destination, 22 is a host name, 23 is a flag, 24 is a column of communication path, and 25 to 28 are items. Other configurations are the same as those in FIG.

Next, the operation will be described. FIG. 7 is an explanatory diagram showing the operation of the communication device according to the second embodiment of the present invention. As shown in FIG. 7A, certain communication programs 29 and 30 are provided between the monitoring device 1 and the monitored device 2a.
However, it is assumed that a process of repeating transmission and reception of data on the communication path 6a by the TCP communication procedure is performed. At this time, the items 26 and 27 of FIG. As shown in FIG. 7B, the monitored device 2
It is assumed that a failure has occurred in the cable between the communication device 6a and the communication path 6a, and both the monitoring device 1 and the monitored device 2a have detected the failure with the configuration shown in the first embodiment. At this time, the communication programs 29 and 30 that have been performing the transmission processing by the TCP communication are stopped due to the occurrence of a cable failure. However, due to the TCP function, the data stored in the transmission area is stored for a certain period of time.

In this case, the monitoring device 1 and the monitored device 2a
Are synchronized with each other, and each communication path is changed from the communication path 6a to the communication path 6
Switch to b. Hereinafter, processing in each of the monitoring device 1 and the monitored device 2a will be described. In the monitoring device 1, the following processing is sequentially performed by the specific communication path switching device 15. First, as shown in item 28 of FIG. 6B, item 26 of FIG. 6A is deleted. Next, a setting is made in item 27 of FIG. 6A so that communication to the monitored device 2a is performed via the communication path 6b. Further, the item 26 in FIG. 6A is registered. On the other hand, even on the monitored device 2a, the specific communication path switching device 1
By 5a, the setting for the monitoring device 1 is changed via the communication path 6b in the same manner as the monitoring device 1.

By the above processing, as shown in FIG. 7C, the communication path between the monitoring apparatus 1 and the monitored apparatus 2a is changed to the communication path 6b and stored in the TCP transmission area. The data is transmitted to the communication path 6b.
The change of the destination is performed in the IP layer below the TCP layer, so that the TCP layer is not affected. Therefore, the process that has performed the TCP communication can continue the same processing as before the occurrence of the failure.

As described above, according to the second embodiment, when a failure occurs in the communication path 6a by the specific communication path switching devices 15 and 15a on the monitoring device 1 and the monitored device 2a, data is transmitted. Since the data is temporarily stored, the route table 20 is updated to the normal communication route 6b, and the temporarily stored data is transmitted via the normal communication route 6b. In addition, there is an effect that the monitored device 2a can continue the communication operation. In addition, there is an effect that the program can be applied as it is without taking any special measures to a program that realizes transmission and reception by TCP.

Embodiment 3 FIG. 8 is an explanatory view showing a route table of a communication device according to a third embodiment of the present invention. In the third embodiment, in the configuration shown in the second embodiment, The communication path used for communication is determined by registering in advance all items of the name or monitored device name and the communication path and setting flags by the specific communication path switching devices 15 and 15a.

Next, the operation will be described. As shown in FIG. 8, for example, an item 31 indicating a normal destination and an item 32 indicating an evacuation destination are registered in the B-HOST, which is the monitored device 2a, and communication with the normal destination is normally performed. Is carried out. If a failure between the monitoring device 1 and the B-HOST that is the monitored device 2a is detected, the specific communication path switching device 15 switches to the evacuation destination by deleting the setting for the normal destination.

As described above, according to the third embodiment, all the items of the monitoring device name or the monitored device name of the communication destination and the communication path are registered in the path table 20 in advance. When an error occurs, it is possible to quickly switch to another communication path.

Embodiment 4 FIG. 9 is an explanatory diagram showing the operation of the communication device according to the fourth embodiment of the present invention. In the fourth embodiment, in the configuration of the first to third embodiments, the monitoring device is replaced by the monitored device and the monitored device is replaced by the monitored device. The monitoring device can be dynamically switched to the monitoring device.

Next, the operation will be described. As shown in FIG. 9A, first, the monitored device 2a,
2b is monitored, and after a certain period of time, FIG.
As shown in (1), the monitoring device 1 is set as a monitored device, the monitored device 2a is set as a monitoring device, and transmission of a confirmation message is started. The subsequent failure detection operation is the same as in the first embodiment.

As described above, according to the fourth embodiment, since the monitoring device can be moved, the monitoring process can be continued without stopping when the monitoring device 1 fails or when maintenance is performed. There is.

Embodiment 5 FIG. FIG. 10 is an explanatory diagram showing the operation of the communication device according to the fifth embodiment of the present invention. In the fifth embodiment, the priority of the monitoring device is set in a setting file (priority setting table) in advance, and the monitored device is monitored. The dynamic switching from the device to the monitoring device is performed according to the priority set in the setting file.

Next, the operation will be described. First, the priority of a monitored device operating as a monitoring device is set in a setting file in advance, and as shown in FIG.
With the configuration shown in (1), when a failure occurs in the monitoring device 1, the monitored device having the highest priority is operated as the monitoring device based on the setting file.

As described above, according to the fifth embodiment, the priority of the monitoring device is set in the setting file in advance, and the dynamic switching from the monitored device to the monitoring device is set in the setting file. Since the monitoring process is performed according to the priority, the monitoring process can be continued without stopping when the monitoring device 1 fails or when maintenance is performed. Also, by setting the priority of the monitoring process, there is an effect that a specific monitored device can be preferentially used as a monitoring device.

Embodiment 6 FIG. FIG. 11 is a flowchart showing the operation of the failure determination device for a communication device according to the sixth embodiment of the present invention.
In the above configuration, the monitored device that first determines the failure of the monitoring device 1 is dynamically switched from the monitored device to the monitoring device.

Next, the operation will be described. In FIG. 11, a failure determination device 5a in each of the monitored devices 2a to 2c
5C, when the confirmation message from all the communication paths 6a and 6b is interrupted and the monitoring device 1 is down in the configuration of the first embodiment, the time at that time is acquired (step ST41), and the confirmation message table is obtained. 10 (step ST42), and transmits a confirmation message based on the updated confirmation message table 10 to another monitored device (step ST43). If a confirmation message from another monitored device is received after transmitting the confirmation message (step ST
44) The transmission time in the confirmation message is checked, and if the transmission time is earlier than the transmission time transmitted by the self-monitoring device (step ST45), the self-monitoring device operates as the monitored device and confirms. Stop sending the message (step ST4)
6). If the transmission has been performed later than the transmission time transmitted by the self-monitoring device (step ST45), the self-monitoring device operates as the monitoring device and continues transmitting the confirmation message.

As described above, according to the sixth embodiment, the monitored device that first determines the failure of the monitoring device 1 is:
Since the monitored device is dynamically switched from the monitored device to the monitoring device, the monitoring device 1 can be moved, and the monitoring process can be continued without stopping when the monitoring device 1 fails or when maintenance is performed. . In addition, any monitored device on the network can be a monitoring device, and a monitored device that can afford processing can become a monitoring device by transmitting a confirmation message first, and the effect of load balancing of computer resources can be improved. Bring.

[0039]

As described above, according to the first aspect of the present invention, a confirmation message is transmitted from a monitoring device to a plurality of monitored devices via two communication paths, and the plurality of monitored devices are transmitted. Is configured to determine the failure points of the two communication paths and the plurality of monitored devices based on the response messages returned from the communication paths via the two communication paths, so that the failure points can be specified and the failure points can be quickly identified. There is an effect that recovery measures can be realized.

According to the second aspect of the present invention, the monitoring device and the plurality of monitored devices include a telegram transmitting device, a telegram receiving device, and a fault determining device, and the monitoring device includes two monitoring devices from the telegram transmitting device of the monitoring device. A confirmation message is transmitted to the message receiving devices of the plurality of monitored devices via the communication paths of the plurality of monitored devices, and the message transmitting devices of the plurality of monitored devices are returned to the message receiving devices of the monitoring devices via the two communication paths. Based on the received response message, the fault determination device of the monitoring device
The communication path of this book and the fault location of a plurality of monitored devices are determined, and the fault location is transmitted to the plurality of monitored devices as a confirmation message, so that the fault location can be identified and the fault location can be quickly restored. There is an effect that measures can be realized. In addition, since the fault location can be recognized by all of the plurality of monitored devices, there is an effect that a quick recovery measure of the fault location can be realized in each monitored device.

According to the third aspect of the present invention, when no confirmation message is received at the monitored device via the two communication paths by the monitored message receiving device, the monitored device transmits the message. A confirmation message is transmitted from the device to the message receiving device of another monitored device via two communication paths,
Based on a response message returned from the message transmission device of the other monitored device to the message reception device of the monitored device via the two communication paths in response to the reception of the confirmation message of the message reception device of the other monitored device. In this configuration, a failure of the monitoring device or two communication path failures is determined by the failure determination device of the monitored device, so that a failure of the monitoring device or two communication path failures can be determined. This has the effect that quick recovery measures can be realized.

According to the fourth aspect of the present invention, when the failure determination device of the monitoring device determines that there is a failure in the communication path, the communication destination item in the route table in which communication is disabled is disabled. At the same time, the data being communicated is temporarily saved to stop the data transmission, and the items of the disabled monitoring device name or monitored device name and the normal communication route in the route table are enabled. And a specific communication path switching device for transmitting the once stored data to a monitoring device or a monitored device of a communication destination via a normal communication path corresponding to the newly enabled item. Therefore, even if a failure occurs in the communication path, the monitoring device and the monitored device can continue the communication operation.

According to the fifth aspect of the present invention, all the items of the monitoring device name or the monitored device name of the communication destination and all the items of the communication route are registered in the route table in advance, and set to be enabled or disabled by the specific communication channel switching device. Therefore, when an abnormality occurs in a communication path, the communication path can be quickly switched to another communication path.

According to the present invention, the monitoring device can be dynamically switched to the monitored device and the monitored device can be dynamically switched to the monitoring device. There is an effect that the monitoring process can be continued without stopping.

According to the seventh aspect of the present invention, the priority setting table in which the priority of the monitoring device is set in advance is provided, and the dynamic switching from the monitored device to the monitoring device is performed in the priority setting table. Since the monitoring is performed according to the set priority, there is an effect that the monitoring process can be continued without being stopped at the time of failure or maintenance of the monitoring device. Further, by setting the priority of the monitoring process, there is an effect that a specific monitored device can be preferentially used as a monitoring device.

According to the eighth aspect of the present invention, the monitored device which first determines the failure of the monitoring device is dynamically switched from the monitored device to the monitoring device, so that the monitoring device can be moved. Thus, there is an effect that the monitoring process can be continued without stopping when a failure or maintenance of the monitoring device occurs. In addition, any monitored device on the network can be a monitoring device, and a monitored device that has a margin for processing can be a monitoring device by transmitting a confirmation message first, thereby causing load distribution of computer resources. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a communication device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a confirmation message table.

FIG. 3 is a flowchart illustrating an operation of the monitoring device.

FIG. 4 is a flowchart showing the operation of the monitored device.

FIG. 5 is a block diagram showing a communication device according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a route table.

FIG. 7 is an explanatory diagram showing an operation of the communication device according to the second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a route table of a communication device according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an operation of the communication device according to the fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an operation of a communication device according to a fifth embodiment of the present invention.

FIG. 11 is a flowchart showing an operation of a failure determination device for a communication device according to a sixth embodiment of the present invention.

FIG. 12 is a block diagram showing a conventional communication device.

[Explanation of symbols]

1 monitoring device, 2a-2c monitored device, 3, 3a-3
c message transmission device, 4, 4a-4c message reception device,
5, 5a-5c failure determination device, 6a, 6b communication path, 15, 15a, 15b specific communication path switching device, 20
Route table.

Claims (8)

[Claims] 1. A monitoring device connected to two communication paths, and a plurality of monitored devices connected to the two communication paths, respectively, wherein the monitoring device and the plurality of monitored devices are connected to each other. In the communication device for transmitting and receiving information between the plurality of monitored devices, the monitoring device transmits confirmation messages to the plurality of monitored devices via the two communication paths, and transmits the confirmation messages in response to reception of the confirmation messages. A communication device for determining a fault location of the two communication paths and the plurality of monitored apparatuses based on a response message returned from the monitored apparatus via the two communication paths. 2. A monitoring device connected to two communication paths, and a plurality of monitored devices respectively connected to the two communication paths, wherein the monitoring device and the plurality of monitored devices are connected to each other. In a communication device that transmits and receives information between the monitoring devices, the monitoring device and the plurality of monitored devices include a message transmission device, a message reception device, and a failure determination device, and the monitoring device is configured to transmit a message from the message transmission device of the monitoring device. 2 above
A confirmation message is transmitted to the message receiving device of the plurality of monitored devices via the communication path of the book, and the plurality of monitored devices are transmitted in response to the receipt of the confirmation message of the message receiving device of the plurality of monitored devices. Based on the response message returned from the message transmitting device of the monitoring device to the message receiving device of the monitoring device via the two communication paths, the fault determining device of the monitoring device determines the two communication routes and the plurality of received messages by the failure determination device of the monitoring device. A communication device characterized by determining a fault location of a monitoring device, and transmitting the fault location as a confirmation message to the plurality of monitored devices. 3. When a confirmation message is not received at all by a message receiving device of the monitored device via two communication paths, the monitored device transmits the two confirmation messages from the message transmitting device of the monitored device. A confirmation message is transmitted to the message receiving device of the other monitored device via the communication path of the other device, and the message of the other monitored device is received in response to the reception of the confirmation message of the message receiving device of the other monitored device. Based on a response message returned from the transmitting device to the message receiving device of the monitored device via the two communication paths, the failure determining device of the monitored device determines whether the monitoring device has failed or the two communication routes. The communication device according to claim 2, wherein a failure is determined. 4. It is provided in the monitoring device and the monitored device,
A path table in which the names of the monitoring apparatuses or monitored apparatuses at the communication destinations and the communication paths are registered, and a fault in the communication path currently provided in the monitoring apparatus and the monitored apparatus, which is being communicated by the fault determining apparatus of the monitoring apparatus. When it is determined that there is an error, the items of the monitoring device name or the monitored device name and the communication route of the communication destination in the route table, which cannot be communicated by the communication route determined to have the fault, are disabled, and The data being communicated is temporarily stored in the monitoring device or the monitored device on the transmitting side, and the data is transmitted to the monitoring device or the monitored device via the communication path corresponding to the disabled item in the routing table. The transmission is stopped, and the monitoring device name or the monitored device name of the disabled communication destination and the item of the normal communication path are enabled in the routing table, and the transmission is performed. To send data once stored in the monitoring device or monitored device to the monitoring device or monitored device of the communication destination via the normal communication path corresponding to the newly enabled item in the routing table 4. A communication path switching device, comprising:
The communication device according to claim 1. 5. A route table in which all items of a communication destination monitoring device name or monitored device name and a communication route are registered in advance, and are set to be enabled or disabled by a specific communication path switching device. The communication device according to claim 4, wherein is determined. 6. The communication device according to claim 1, wherein a monitoring device can be dynamically switched to a monitored device, and a monitored device can be dynamically switched to a monitoring device. 7. A priority setting table in which priorities of monitoring devices are set in advance, and dynamic switching from a monitored device to a monitoring device is performed according to the priority set in the priority setting table. 7. The communication device according to claim 6, wherein the communication is performed. 8. The communication device according to claim 3, wherein the monitored device that first determines the failure of the monitoring device is dynamically switched from the monitored device to the monitoring device.