Network management program, network system, and network management method

Abstract

The present disclosure relates to a network management program, a network system, and a network management method. A conventional network management method has a problem that there is a high possibility that a setting error of communication software occurs. According to one embodiment, a non-transitory computer readable medium includes a network management program executed in a master device, reads out system information pre-stored in a slave device in an SNMP-compliant process, reads out protocol information from the slave device by using an object ID described in the system information thus read out, the protocol information describing a communication protocol that the slave device can use, and starts communication with the slave device by executing software corresponding to the communication protocol with reference to the protocol information thus read out.

Description

[0001] Cross-reference to related applications

[0002] The disclosure of Japanese Patent Application No. 2021-035128, filed on March 5, 2021 (including the specification, drawings and abstract), is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to a non-transient computer-readable medium including a network management program, a network system, and a network management method. For example, this invention relates to a non-transient computer-readable medium including a network management program, a network system, and a network management method for managing a network configured such that slave devices connected to a network managed by a master device can be added or replaced. Background Technology

[0004] In recent years, it has been practiced to connect various devices to networks to build a system. As one such network system, there exists an industrial network system in which devices in factories, etc., are interconnected via a network to monitor and control their operational status. In such an industrial network system, multiple devices are centrally introduced with the overall system configuration and specifications predetermined. Furthermore, in the event of a device failure, it is replaced by a new device. Additionally, new devices are added to the system after its construction. However, in an industrial network system, when a device is replaced or added, the device to be replaced or added may use a different communication protocol than the one set during system construction. Therefore, Patent Document 1 discloses a technique for delivering setup information to devices using different communication protocols.

[0005] In the technology described in Patent Document 1, the management device delivers configuration information to the device (e.g., a network device). Specifically, the management device described in Patent Document 1 selects to preferentially use a second protocol, which is different from the first protocol and is SNMP compared to the first protocol, for configuration purposes. If the device to which the configuration information is intended supports the second protocol, the management device delivers configuration information based on the specifications of the second protocol to the device. If the configuration device selects to preferentially use the second protocol compared to the first protocol and the device to which the configuration information is intended does not support the second protocol, the management device delivers configuration information based on the specifications of the first protocol to the device.

[0006] The disclosed technologies are listed below.

[0007] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2018-41146 Summary of the Invention

[0008] However, in a network system, when a network device (e.g., a slave device) managed by a management device (e.g., a master device) is to be replaced or added, it is unknown whether a communication protocol that can be used by both the master and slave devices exists. For this reason, when a new slave device is introduced, the communication protocol used by the slave device is manually analyzed using a network analyzer or similar tool, and the communication protocol used initially is manually set based on the analysis results. At this time, the software related to the communication protocol is manually introduced, but due to manual operation, errors such as different software being applied may occur. The technology described in Patent Document 1 cannot solve this problem.

[0009] Other purposes and new features will become clear from the description in this specification and the accompanying drawings.

[0010] According to one embodiment, a non-transient computer-readable medium includes a network management program to be executed by an operating unit of a master device. The master device is configured to manage slave devices connected to a network based on a Simple Network Management Protocol (SNMP). The network management program includes: a first request process configured to generate a first request command for requesting system description information and send the generated first request command to the slave device, the system description information containing system information of the slave device; a second request process configured to generate a second request command including a specific object ID if the system description information received from a first response command contains a specific object ID, and send the second request command to the slave device, the first response command being a response from the slave device to the first request command, the specific object ID indicating protocol information that the slave device can use; and a communication software selection process configured to, after switching the communication software used to perform communication with the slave device to communication software corresponding to a protocol that the slave device can use, initiate communication with the slave device by referring to a protocol name corresponding to the slave device, the protocol name being included in the second response command, the second response command being a response from the slave device to the second request command.

[0011] According to one embodiment, the network management program can reduce configuration errors of the communication protocol used between slave and master devices. Attached Figure Description

[0012] Figure 1 This is a block diagram of a network system according to the first embodiment.

[0013] Figure 2 This is a sequence diagram used to explain the process of adding a slave device without applying the network management method according to the first embodiment.

[0014] Figure 3 This is a sequence diagram used to explain the process of adding a slave device when applying the network management method according to the first embodiment.

[0015] Figure 4 This is a sequence diagram used to explain the steps of adding a slave device in a network system according to the first embodiment.

[0016] Figure 5 This is a diagram used to explain the commands to be sent or received in the network system according to the first embodiment.

[0017] Figure 6 This is a flowchart used to explain the operation when a master device receives a response command in a network system according to the first embodiment.

[0018] Figure 7 This is a diagram used to explain the commands to be sent or received in the network system according to the second embodiment.

[0019] Figure 8 This is a sequence diagram used to explain the process of adding a slave device when applying the network management method according to the third embodiment. Detailed Implementation

[0020] For clarity, the following descriptions and figures have been appropriately omitted or simplified. Furthermore, each element described in the figures as a functional block performing various processes can be configured in hardware by a CPU, memory, and other circuitry, or implemented in software by a program loaded into memory. Therefore, those skilled in the art will understand that these functional blocks can be implemented in hardware only, software only, or a combination thereof, and are not limited to any of these. Note that in the various figures, the same reference numerals are applied to the same elements, and repeated explanations are omitted where necessary.

[0021] Furthermore, the aforementioned program can be stored using any of a variety of non-transient computer-readable media and can be provided to a computer. Non-transient computer-readable media include various types of tangible storage media. Examples of non-transient computer-readable media include magnetic recording media (e.g., floppy disks, magnetic tapes, and hard disk drives), optical-magnetic recording media (e.g., optical discs), CD-ROMs (Read-Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash memory ROMs, and RAMs (Random Access Memory)). In addition, the program can be provided to a computer via various types of transient computer-readable media. Examples of transient computer-readable media include electrical signals, optical signals, and electromagnetic waves. Each transient computer-readable medium can provide the program to the computer via a wired communication path such as a power line or optical fiber, or via a wireless communication path.

[0022] (First Embodiment)

[0023] Figure 1 A block diagram of a network system 1 according to a first embodiment is shown. Figure 1 As illustrated in the diagram, in the network system 1 according to the first embodiment, the master device 10 is connected to a plurality of slave devices (in...) via network 20. Figure 1 The example shows each of the slave devices (from device 11 to 13).

[0024] Master device 10 is configured to manage each of slave devices 11 to 13. Furthermore, master device 10 and each of slave devices 11 to 13 obtain the information necessary for operation from each other by sending or receiving commands conforming to SNMP (Simple Network Management Protocol) during initial setup. SNMP is a protocol standardized by RFC 1157 for the purpose of master devices monitoring slave devices. Note that the master device can also be referred to as a manager device. Additionally, slave devices can also be referred to as agent devices.

[0025] In this SNMP, when information about a device needs to be obtained from another device, a request command (e.g., a command called GET REQUEST) is sent. Furthermore, the device receiving the request command sends a response command (e.g., GET RESPONSE) as a reply to the request command to the other device.

[0026] Here, in SNMP, the information desired to be obtained from the other device is specified in a format called an object ID. The device sending the request command sends the request command to the other device so that the object ID is included in the request command. The details of the object ID format will be described later.

[0027] Subsequently, a network management method for a network system according to the first embodiment will be described. In the following description, in order to explain the features of the network management method according to the first embodiment, a manual network management method will be described as a comparative example, and the manual network management method according to the comparative example and the network management method according to the first embodiment will be described in comparison.

[0028] therefore, Figure 2 The diagram illustrates a sequence of steps for adding a slave device without applying the network management method according to the first embodiment (e.g., a comparative example). Note that the process for replacing the slave device is the same as the process for adding the slave device to the network. Therefore, in the context of including Figure 2 The operation description of the steps illustrated in the figure will describe the network management method when a slave device is added.

[0029] like Figure 2As illustrated in the diagram, in the network management method of the comparative example, after a slave device is added, a trial operation for protocol communication is performed on each of the master and slave devices (steps S101 and S102). During this trial operation, the operator adding the slave device uses a network analyzer or similar tool to analyze the communication protocols that the slave device to be added to the network can use (step S103). Then, if the master device cannot use the same communication protocol as determined in step S103, communication software corresponding to the communication protocol that the slave device can use is installed on the master device (step S104). After the software preparation is complete, communication using a protocol that can be used by both the master and slave devices begins (steps S105 and S106).

[0030] exist Figure 2 In the process illustrated, the operator manually confirms the communication protocols that each of the master and slave devices can use, and prepares software for the communication protocols that the master and slave devices can use together (e.g., steps S103 and S104). To this end, according to... Figure 2 In the network management method of the comparative example illustrated in the figure, problems such as setting errors may occur in steps S103 and S104.

[0031] Therefore, in the network management method according to the first embodiment, the communication protocol at the time of introducing the slave device is confirmed to be executed using a network management program executed by the master device. Each of the master device and slave device joining the network system includes an operating unit capable of executing software, and uses the software to execute various processes. Furthermore, the network management method according to the first embodiment is implemented by a network management program. This network management program includes first software to be executed by the operating unit of the master device and second software to be executed by the operating unit of the slave device. The first software and the second software together perform communication according to SNMP. In addition, the network management method according to the first embodiment has one of the following features: system information is pre-stored in the slave device, the system information describes information conforming to the SNMP object ID (hereinafter referred to as "specific object ID") format, and information related to protocols compatible with the slave device is specified by the specific object ID.

[0032] Subsequently, Figure 3 The diagram illustrates a sequence of steps for adding a slave device when applying the network management method according to the first embodiment. Figure 3As illustrated in the diagram, the network system 1 according to the first embodiment first performs protocol analysis communication to analyze available communication protocols (steps S1 and S2). In this protocol analysis communication, the master device and the slave device communicate based on SNMP. Then, the master device switches the communication software so that the slave device, which was controlled by the master device in the protocol analysis communication, can use the available communication protocol (step S3). Then, based on the completion of the communication software switching at step S3, the master device and the slave device begin communication based on a predetermined communication protocol (steps S4 and S5).

[0033] Here, the protocol analysis communication in steps S1 and S2 will be described in more detail. Therefore, Figure 4 The illustration shows a sequence diagram for explaining the process of adding a slave device in a network system 1 according to a first embodiment.

[0034] like Figure 4 As illustrated in the diagram, in the network management method according to the first embodiment, steps S10 to S16 are performed as protocol analysis communication execution steps. In step S10, the master device generates a first request command (e.g., a GETREQUEST sent from the master device to the slave device between steps S10 and S11) to request system description information (e.g., sysDescr), which includes the slave device's system information as an object ID in an SNMP-compliant format. Then, when the process at step S10 completes, the master device sends the first request command to the slave device.

[0035] Then, the slave device identifies the first request command (step S11). Subsequently, the slave device reads the system description information stored as sysDescr from the MIB (Management Information Base) storage memory based on the object ID included in the first request command, and generates a first response command including sysDescr (e.g., a GET RESPONSE sent from the slave device to the master device between steps S12 and S13). When the process at step S12 is completed, the slave device sends the first response command to the master device.

[0036] Here, in SNMP, the MIB storage is defined as a data storage area that can be read by an object ID. Furthermore, various information, including at least the sysDescr defined in SNMP, which describes the device's settings, is stored in this MIB storage. Additionally, in the network system 1 according to the first embodiment, a specific object ID (e.g., an object ID specifying access to supported protocols) is described later in the sysDescr stored in the slave device using an object ID-based description format.

[0037] When the master device receives the first response command, it refers to sysDescr included in the first response command to identify the object ID indicated by the supported protocol (step S13). The master device uses this supported protocol identified in step S13 as the object ID to generate a second request command (e.g., a GET REQUEST sent from the master device to the slave device between steps S14 and S16) (step S14). The master device then sends the second request command generated in step S14 to the slave device.

[0038] When the slave device receives the second request command, it refers to the object ID to identify the supported protocol (step S15). Based on the object ID identified in step S15, the slave device reads protocol information compatible with the slave device from the memory storing supported protocols and generates a second response command specifying the compatible protocol information (e.g., a GET RESPONSE sent from the slave device to the master device between steps S16 and S3) (step S16). Note that the protocol information describes the protocol names that the slave device can use. The slave device then sends the second response command generated in step S16 to the master device.

[0039] When the master device receives the second response command, it switches the communication software in step S3 according to the command. During this software switching process, the master device identifies the protocol name that the slave device can use by referring to the protocol information contained in the second response command, and switches the communication software to be executed when communicating with the slave device to the communication software corresponding to the identified protocol. Then, upon completion of this software switching process, the master device begins communication between the master device and the slave device (steps S4 and S5).

[0040] Here, the process from steps S10 to S16 will be described in detail, along with specific examples of information regarding the object ID, sysDescr, and supported protocols. Therefore, Figure 5 The diagram illustrates commands sent or received in a network system according to the first embodiment.

[0041] First, the object ID specified in sysDescr is the object ID defined by SNMP. Its first field has a value of 1 (iso); its second field has a value of 3 (org); its third field has a value of 6 (dod); its fourth field has a value of 1 (Internet); its fifth field has a value of 2 (mgmt); its sixth field has a value of 1 (MIB-2); its seventh field has a value of 1 (system); and its eighth field has a value of 1 (sysDescr).

[0042] When the device receives an object ID specifying sysDescr, it reads sysDescr from the MIB storage. For example... Figure 5 As illustrated in the diagram, sysDescr contains various system information about the agent device, and the value of the location specifying the storage protocol information is the object ID of the supported protocol, which is described as one of the system information.

[0043] The device generates a first response command including the sysDescr and sends it to the master device. Here, the object ID described in the sysDescr included in the first response command has the following values: first field 1 (iso), second field 3 (org), third field 6 (dod), fourth field 1 (Internet), fifth field 4 (private), sixth field 1 (enterprise), and seventh field n (supported protocols). Figure 5 In the example shown, the value of the seventh field is set to n, but this value can be arbitrarily determined based on the purpose of the device.

[0044] The master device sends the object ID of the supported protocol as a second request command to the slave device. The slave device then reads information about the supported protocols from memory based on the second request command. Furthermore, the slave device sends a second response command containing the read information about the supported protocols to the master device. This information about the supported protocols describes the protocol names compatible with the slave device. The master device refers to the protocol names described in the supported protocols to determine the communication software used to communicate with the slave device.

[0045] Since one of the features of the master device according to the first embodiment is that it operates upon receiving a response command, the process of the master device receiving a response command will be described in detail. Therefore, Figure 6 This is a flowchart used to explain when a master device receives a response command in a network system according to the first embodiment.

[0046] like Figure 6 As illustrated in the diagram, when the master device receives a response command (step S21), the master device performs analysis on the object ID included in the response command (step S22). If the object ID is not the sysDescr and supported protocol specified in the object ID analysis at step S22, the master device executes the process based on the MIB information included in the response command and terminates the process used for the response command (step S23).

[0047] Furthermore, if the analysis result of the object ID at step S22 is sysDescr (for example, Figure 4In step S13), the master device checks whether an object ID specifying a supported protocol exists in the received sysDescr (step S28). If it is determined in step S28 that no object ID specifying a supported protocol exists, the master device executes the process based on the contents of the received sysDescr and terminates the process (step S30). On the other hand, if it is determined in step S28 that an object ID specifying a supported protocol exists in sysDescr, the master device sends a second request command including the object ID indicating the supported protocol to the slave device and terminates the process used to respond to the command (step S29).

[0048] Furthermore, the result of analyzing the object ID in step S22 is in the case of supported protocols (e.g., Figure 4 In step S3), the master device analyzes the protocol information (e.g., information about supported protocols) contained in the second response command (step S24). Then, based on the analysis results at step S24, the master device determines whether there exists a communication protocol that can be used by both the master device and the slave device (step S25). If it is determined in the determination process at step S25 that a communication protocol that can be used by both the master device and the slave device exists, the master device switches the communication software to be executed to the communication software corresponding to the communication protocol that was determined to be commonly used, and terminates the process used to respond to the command (step S26). Furthermore, if it is determined in the determination process at step S25 that no communication protocol that can be used by both the master device and the slave device exists, the master device notifies the operator or administrator that no protocol can be used by both the master device and the slave device, and terminates the process used to respond to the command (step S27).

[0049] As described above, in the network system 1 according to the first embodiment, a specific object ID for reading protocol information is described in system information (e.g., sysDescr) that can be invoked by an SNMP process. This object ID, which is not defined for the protocol information, is used to invoke the memory of a slave device installed in the network to be joined via SNMP. After the slave device stores this system description information, when a response command includes the specific object ID, the master device is enabled as a process to generate a request command specifying the specific object ID. Because the network system 1 according to the first embodiment has this configuration, the master device can learn the communication protocols that the slave device can use through SNMP-compliant communication processing between the master device and the slave device.

[0050] Because the master device directly learns the communication protocols that the slave device can use through program operation in this way, no manual operation is required. Therefore, configuration errors when introducing slave devices can be reduced.

[0051] Furthermore, in the network system 1 according to the first embodiment, if there is no communication protocol that can be used by both the master and slave devices, the master device issues a notification of protocol incompatibility to the operator or administrator. Therefore, it becomes easy to introduce communication software compatible with the slave device into the master device without errors.

[0052] (Second Embodiment)

[0053] In the second embodiment, another form of the network management method according to the first embodiment will be described. In the second embodiment, a process will be described in the case where multiple communication protocols are included in supported protocols and are usable by the device.

[0054] therefore, Figure 7 This is a diagram used to explain the sending and receiving commands in a network system according to the second embodiment. For example... Figure 7 As illustrated in the diagram, in the network system according to the second embodiment, the information about the supported protocols to be stored in the slave device differs from that in the network system according to the first embodiment.

[0055] Specifically, in the network system of the second embodiment, as information about supported protocols, the number of protocols compatible with the slave device and multiple corresponding protocol names are described. In the network system according to the second embodiment, Figure 7 The information about supported protocols illustrated in the diagram is included in the second response command, which is generated as a reply to the second request command and includes the supported protocols as object IDs.

[0056] Furthermore, when the master device according to the second embodiment receives information about... Figure 7 When the master device receives information about supported protocols, it refers to the protocol name described in the received information and selects a protocol that can be used by both the master and slave devices. Then, the master device switches the communication software to be executed to the communication software corresponding to the selected protocol to begin communication with the slave device.

[0057] As described above, in the network system according to the second embodiment, multiple communication protocols that can be used by the slave device are described. This increases the possibility of matching communication protocols that can be used by both the master and slave devices.

[0058] (Third Embodiment)

[0059] In the third embodiment, yet another embodiment of the network management method according to the first embodiment will be described. In the third embodiment, a method for managing communication software when multiple slave devices exist in the network will be described.

[0060] therefore, Figure 8The diagram illustrates a sequence of steps for adding a slave device when applying the network management method according to the third embodiment. Figure 8 In the example illustrated, in the network system according to the third embodiment, the master device communicates with the first slave device and the second slave device. Here, in Figure 8 In the example illustrated, the first slave device is the device that is being added to the network, and the second slave device is a device that has already joined the network. Furthermore, the first slave device can use communication protocols A to C, and the second slave device can use communication protocols C to E.

[0061] like Figure 8 As illustrated in the diagram, in the network system according to the third embodiment, the master device and the first slave device perform a first protocol analysis communication (steps S31 and S32) between them. In this first protocol analysis communication, Figure 4 The processes at steps S10 to S16 shown in the diagram are executed. Then, through communication analysis using the first protocol, the master device identifies that the communication protocols that the first slave device can use are protocols A to C.

[0062] Subsequently, in the network system according to the third embodiment, the master device and the second slave device perform a second protocol analysis communication (steps S41 and S42) between them. In this second protocol analysis communication, Figure 4 The processes S10 to S16 illustrated in the diagram are executed between the master device and the second slave device. Then, through communication analysis using the second protocol, the master device identifies that the communication protocols that the second slave device can use are protocols C to E.

[0063] Subsequently, in the network system according to the third embodiment, based on information about supported protocols obtained through the first protocol analysis communication and the second protocol analysis communication, the master device switches the communication software to be executed to communication software corresponding to a communication protocol (e.g., protocol C) that can be used by both the first and second slave devices (step S33). After this communication software switch, the master device begins communication with the first and second slave devices (steps S34, S35, and S36).

[0064] As described above, in the network system according to the third embodiment, by performing protocol analysis communication with each of the plurality of slave devices, the master device can identify a communication protocol compatible with each of the plurality of slave devices. As a result, in the network system according to the third embodiment, the master device can identify a communication protocol that can be used by the plurality of slave devices and perform communication with the plurality of slave devices using communication software corresponding to the communication protocol.

[0065] As described above, the invention made by the inventors of this application has been specifically described based on embodiments. However, the invention is not limited to the described embodiments, and various modifications can be made without departing from the spirit of the invention, which is self-evident.

Claims

1. A non-transient computer-readable medium comprising a network management program to be executed by an operating unit of a master device, the master device being configured to manage slave devices connected to a network based on a Simple Network Management Protocol (SNMP), the network management program comprising: The first request process is configured to generate a first request command for requesting system description information and send the generated first request command to the slave device, wherein the system description information includes the system information of the slave device; The second request process is configured to generate a second request command including the specific object ID if the system description information received by the first response command contains a specific object ID, and send the second request command to the slave device. The first response command is a reply from the slave device in response to the first request command. The specific object ID indicates the protocol information that the slave device can use. as well as The communication software selection process is configured to refer to a protocol name corresponding to the slave device, so that communication with the slave device begins after the communication software used to perform communication with the slave device is switched to communication software corresponding to a protocol that the slave device can use. The protocol name is included in a second response command replied from the slave device in response to the second request command. In the communication software selection process, the administrator is notified that there is no protocol that the master device and the slave device can use together in the following cases: the protocol name that the master device can use is not included in the protocol name corresponding to the slave device and is included in the second response command.

2. The non-transient computer-readable medium according to claim 1, The specific object ID described in the system description information is described in advance in the system description information.

3. The non-transient computer-readable medium according to claim 1, Each of the first request command, the second request command, the first response command, and the second response command includes an object ID conforming to the SNMP format.

4. The non-transient computer-readable medium according to claim 1, Multiple protocol names are included in the protocol names corresponding to the slave device and included in the second response command, and During the communication software selection process, a protocol compatible with the slave device is selected from the plurality of protocol names, and the communication software is switched to the communication software corresponding to the selected protocol.

5. The non-transient computer-readable medium according to claim 1, The slave device includes multiple slave devices, and During the communication software selection process, communication with the plurality of slave devices is initiated by referring to the protocol name included in the second response command received from each of the plurality of slave devices and the communication software corresponding to the protocol that can be used among the plurality of slave devices.

6. A network system comprising slave devices and master devices connected to a network, the slave devices and master devices interconnected to the network based on the Simple Network Management Protocol (SNMP), the network system comprising: The first software is executed by the operation unit of the main device; as well as The second software is executed by the operating unit of the slave device. The first software is configured to execute: The first request process is configured to generate a first request command for requesting system description information and send the generated first request command to the slave device, wherein the system description information includes the system information of the slave device; The second request process is configured to generate a second request command including the specific object ID if the system description information received by the first response command contains a specific object ID, and send the generated second request command to the slave device. The first response command is a reply from the slave device in response to the first request command. The specific object ID indicates the protocol information that the slave device can use. as well as The communication software selection process is configured to refer to a protocol name corresponding to the slave device, so as to initiate communication with the slave device after switching the communication software used to perform communication with the slave device to communication software corresponding to a protocol that the slave device can use, wherein the protocol name is included in a second response command replied from the slave device in response to the second request command. The second software is configured to execute: A first response process is configured to generate a first response command in response to a first request command, the first response command containing the system description information stored in the slave device, and to send the generated first response command to the master device; as well as The second response process is configured to, when the specific object ID is included in the second request command, generate a second response command containing the protocol information and send the generated second response command to the master device. The protocol information describes the protocol name corresponding to the slave device specified by the specific object ID. The administrator is notified that there is no protocol that the master device and the slave device can use together if: the protocol name that the master device can use is not included in the protocol name corresponding to the slave device and is included in the second response command.

7. A network management method, based on software processing and command execution by each of a master device and a slave device, the commands being sent or received between the master device and the slave device, the master device managing the slave device based on a Simple Network Management Protocol (SNMP), the network management method comprising: The first request process is configured to generate a first request command for requesting system description information by the master device, and send the generated first request command to the slave device, wherein the system description information includes the system information of the slave device; A first response process is configured to, in response to the first request command, generate a first response command by the slave device, the first response command containing the system description information stored in the slave device, and send the generated first response command to the master device; The second request process is configured to, when the system description information received through the first response command contains a specific object ID, generate a second request command including the specific object ID by the master device and send the generated second request command to the slave device, wherein the specific object ID indicates protocol information that the slave device can use; The second response process is configured to, when the second request command includes the specific object ID, have the slave device generate a second response command containing the protocol information and send the generated second response command to the master device, wherein the protocol information describes the protocol name corresponding to the slave device specified by the specific object ID; as well as The communication software selection process is configured so that the master device, referring to the protocol name corresponding to the slave device, initiates communication with the slave device after the communication software used to perform communication with the slave device is switched to communication software corresponding to a protocol usable by the slave device. The protocol name is included in the second response command. The administrator is notified that there is no protocol that the master device and the slave device can use together if: the protocol name that the master device can use is not included in the protocol name corresponding to the slave device and is included in the second response command.

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