JP5786643B2 - Communication network system, relay device in the same system, and relay processing program - Google Patents

Description

  The present invention is particularly suitable for an application that performs control such as metering of gas, electricity, water supply, etc., shut-off, return, etc. via a communication network, a communication network system, a relay device in the system, and a relay processing program About.

Conventionally, for example, in a gas metering system that centrally manages metering of LP gas at home, automatic metering is performed by making a silent call to the user's home from a remote location via an analog or digital telephone line and obtaining the response. I was going. According to the automatic meter reading system using the telephone line, the telephone line is occupied during the meter reading, and inconveniences such as a long time for meter reading occur when targeting multiple households. To do. In order to solve this problem, IP (Internet
Protocol) An automatic meter reading system that performs meter reading via a network has been proposed (see, for example, Patent Document 1).

  In the automatic meter reading system using the IP network disclosed in Patent Document 1, each IP terminal has a terminal ID for individual identification and a fixed IP address. The contents are registered in the storage device of the management server to which the fixed IP address is assigned, and the management server and the plurality of IP terminals managed and operated by the terminal management center based on the associated terminal ID and IP address. It enables mutual communication using an IP network.

JP 2002-27569 A

  In the automatic meter reading system using the IP network described above, the IP address assigned to the IP terminal is moved in order to cope with the dynamic IP address assignment generally used in the wide area network (WAN). The IP address is periodically notified from the IP terminal to the management server. The management server receives this IP address and registers it in the storage device, thereby managing the IP address dynamically assigned to the IP terminal for communication.

  However, in order to cope with an IP address dynamically assigned by an existing automatic meter reading system constructed on the assumption that a fixed IP address is assigned, the equipment needs to be modified, and the modification cost is required. There are other alteration risks. In addition, on the management server side, originally unnecessary communication is required in order to cope with a dynamic IP address. As a result, communication traffic increases and communication cost increases.

  The present invention has been made in order to solve the above-described problems, and when incorporating a network in which an IP address is dynamically assigned into an existing network constructed on the assumption that a fixed IP address is assigned, An object of the present invention is to provide a communication network system, a relay device in the system, and a relay processing program capable of executing an application such as meter reading at a low cost by preventing modification of equipment and preventing an increase in communication traffic.

  In order to solve the above-described problem, a communication network system according to a first aspect of the present invention includes a first terminal group to which a fixed IP address is assigned connected to a management server via a first communication network. And a second network segment in which a second terminal group to which the IP address is dynamically assigned is connected to the management server via a second communication network. In this communication network system, a relay device is connected between the first network segment and the second network segment, and the relay device assigns an IP address dynamically assigned to the second terminal group, It replaces with a virtual IP address as a part of the first network segment, and relays a message transmitted and received between the management server and the second terminal group.

  According to the communication network system according to the first aspect of the present invention, the relay device connected between the first network segment and the second network segment is dynamically assigned to the second terminal group. The address is replaced with a virtual IP address as a part of the first network segment, and a message transmitted and received between the management server and the second terminal group is relayed. When the second network segment dynamically assigned with the IP address is incorporated into the first network segment constructed on the assumption that the IP address is fixedly assigned by the relay device, the existing equipment is modified. Therefore, it is possible to provide a communication network system that realizes an application such as meter reading at a low cost without any modification risk. Further, since no modification of equipment is required, an increase in communication traffic for dealing with a dynamic IP address on the management server side can be prevented, so that communication cost does not increase.

  In the communication network system according to the first aspect of the present invention, the relay device transmits the IP address assigned to the second terminal group dynamically or periodically from the second terminal group. The virtual IP address and the terminal IP address are associated with each other by a transmitted message. According to the present invention, since the communication between the management server and the second terminal group is relayed by the virtual IP address and the terminal IP address associated with each other in the relay device, the management server dynamically moves to the second terminal group. There is no need to manage the assigned IP address, and therefore the processing load for the management is reduced and the throughput of the communication network system is improved.

  In the communication network system according to the first aspect of the present invention, the relay device is transmitted to itself by a RAW socket set as a gateway when the management server transmits a message to the second terminal group. It has the 1st IP communication interface part which receives the message which does not exist. According to the present invention, the relay device receives all messages transmitted from the management server to the second terminal group through a RAW socket set as a gateway by the management server. For this reason, it is possible to relay, for example, a management message such as blocking or returning to all the second terminal groups from the management server.

  In the communication network system according to the first aspect of the present invention, the relay device is associated with a second IP communication interface unit to which a fixed IP address is assigned when communicating with the second terminal group. In the case where a message is transmitted from the management server to the second terminal group, the message is transmitted from the management server by the first IP communication interface unit when the virtual IP address and the fixed IP address are stored. Upon receipt, the IP address assigned to the corresponding terminal is obtained by referring to the storage unit based on the virtual IP address that is the transmission destination of the message, and the second IP communication interface unit is set as the destination. When transmitting a message to the second terminal group and transmitting a message from the second terminal group to the management server, the second communication interface When the message is received from the second terminal group by the source unit, the corresponding virtual IP address is obtained by referring to the storage unit based on the IP address of the terminal that is the source of the message. And a relay processing unit configured to transmit to the management server via the first IP communication interface unit.

  According to the present invention, when the relay device transmits a message from the management server to the second terminal group, when the relay device receives the message from the management server by the first IP communication interface unit, the virtual IP address that is the transmission destination of the message The IP address of the corresponding terminal is obtained by referring to the storage unit, set as the destination, and transmitted to the second terminal group via the second IP communication interface unit. In addition, when the relay device transmits a message from the second terminal group to the management server, when the second communication interface unit receives the message from the second terminal group, the relay device is based on the fixed IP address that is the source of the message. A corresponding virtual IP address is obtained by referring to the storage unit, the virtual IP address is set as a destination, and is transmitted to the management server via the first IP communication interface unit. For this reason, there is no load on the management server between the management server constructed on the premise that a fixed IP address is assigned and the second terminal group to which the IP address is dynamically assigned, and is shut down or restored. Mutual communication such as request messages and meter reading messages is possible.

  A relay device according to a second aspect of the present invention includes a first network segment in which a first terminal group to which a fixed IP address is assigned is connected to a management server via a first communication network, and the IP address is In a network system comprising a second network segment in which a second group of dynamically assigned terminals is connected to the management server via a second communication network, the first network segment and the second network segment It is a relay apparatus connected between. The relay apparatus replaces an IP address dynamically assigned to the second terminal group with a virtual IP address as a part of the first network segment, and connects the management server and the second terminal group. It has a control means which relays the message transmitted / received between, It is characterized by the above-mentioned.

  According to the relay device according to the second aspect of the present invention, the control unit replaces the IP address dynamically assigned to the second terminal group with the virtual IP address as a part of the first network segment, It relays messages sent and received between the management server and the second terminal group. For this reason, when the second network segment dynamically assigned with the IP address is incorporated into the first network segment constructed on the assumption that a fixed IP address is assigned, it is not necessary to modify the existing equipment. Therefore, it is possible to realize an application such as meter reading at a low cost without any risk of modification. Further, since no modification of equipment is required, an increase in communication traffic for dealing with a dynamic IP address on the management server side can be prevented, so that communication cost does not increase.

  In the relay device according to the second aspect of the present invention, the control means uses the RAW socket set as a gateway by the management server when the management server transmits a message to the second terminal group. A first IP communication interface unit that receives a message not addressed, a second IP communication interface unit to which a fixed IP address for communication with the second terminal group is assigned, and an assignment to the second terminal group A storage unit for storing the virtual IP address and the IP address of the terminal associated with each other when the IP address to be dynamically changed or by a message transmitted periodically from the second terminal group; When transmitting a message from the management server to the second terminal group, the first IP communication interface unit transmits the message from the management server. Is received, an IP address of a corresponding terminal is obtained by referring to the storage unit based on the virtual IP address that is a transmission destination of the message, and set as a destination via the second IP communication interface unit. When transmitting to the second terminal group and transmitting a message from the second terminal group to the management server, when receiving the message from the second terminal group at the second communication interface unit, Based on the IP address of the terminal that is the transmission source, the storage unit is referred to obtain a corresponding virtual IP address, the virtual IP address is set as a destination, and the management server is set via the first IP communication interface unit And a relay processing unit that transmits to the network.

  According to the present invention, when the relay processing unit transmits a message from the management server to the second terminal group, when the first IP communication interface unit receives the message from the management server, the relay processing unit receives the virtual IP that is the transmission destination of the message. Based on the address, the storage unit is referred to obtain the IP address of the corresponding terminal, set as a destination, and transmitted to the second terminal group via the second IP communication interface unit. In addition, when the relay processing unit transmits a message from the second terminal group to the management server, when the second communication interface unit receives the message from the second terminal group, the IP address of the terminal that is the source of the message The corresponding virtual IP address is obtained by referring to the storage unit, and the virtual IP address is set as a destination and transmitted to the management server via the first IP communication interface unit. For this reason, there is no load of the management server between the first network segment constructed on the premise that the IP address is fixedly assigned and the second terminal group to which the IP address is dynamically assigned, Mutual communication of request messages such as blocking and restoration and meter reading messages becomes possible.

  In order to solve the above-described problem, the relay processing program according to the third aspect of the present invention is configured such that a first terminal group to which a fixed IP address is assigned is connected to a management server via a first communication network. And a second network group in which a second terminal group to which the IP address is dynamically assigned is connected to the management server via a second communication network, is executed by a computer, A relay processing program used in a relay device connected between the first network segment and the second network segment. The relay processing program replaces the IP address dynamically assigned to the second terminal group in the computer with a virtual IP address as a part of the first network segment, and the management server and the second The process of relaying a message transmitted / received to / from the terminal group is executed.

According to the present invention, when a network in which an IP address is dynamically assigned is incorporated into an existing network that is constructed on the assumption that a fixed IP address is assigned, it is possible to increase communication traffic without requiring modification of equipment. It is possible to provide a communication network system, a relay device in the system, and a relay processing program capable of preventing and executing an application such as meter reading at a low cost.

It is a block diagram which shows the connection form of the communication network system which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of the relay apparatus which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of the management server in FIG. It is a block diagram which shows the internal structure of the wide area network terminal in FIG. It is a sequence diagram which shows the operation | movement between each element which comprises the communication network system which concerns on embodiment of this invention.

  Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as the present embodiment) will be described in detail with reference to the accompanying drawings.

(Configuration of the embodiment)
FIG. 1 is a block diagram showing a connection form of a communication network system 1 according to the present embodiment. As shown in FIG. 1, a communication network system 1 according to this embodiment is a local area network (LAN: Local) to which a fixed IP address is assigned.
Area Network) terminal 11 (first terminal group, hereinafter simply referred to as LAN terminals # 1 (11a) to #n (11d)) is a LAN 12 (Local
A local area segment 10 (first network segment) connected to the management server 13 via an area network) and a wide area network terminal 14 (second terminal group) to which an IP address is dynamically assigned, A wide area segment 20 (second network segment) in which WAN terminals # 1 (14a) to #n (14b) are simply connected to the management server 13 via the IP network 16 (second communication network); It is comprised including.

  The WAN terminals # 1 (14a) and #n (14b) are both connected to the IP network 16 via the routers 15a and 15b. As a feature of the communication network system 1, a relay device 17 is connected between the local area segment 10 and the wide area segment 20. The relay device 17 replaces the IP address dynamically assigned to the WAN terminals # 1 (14a) and #n (14b) with a virtual IP address as a part of the local area segment 10, and the management server 13 and the WAN terminal # 1 (14a) or functions as a control means for relaying a message transmitted / received to / from WAN terminal #n (14b).

  Therefore, for example, as shown in FIG. 2, the relay device 17 includes a RAW socket IP communication interface unit 171 (first IP communication interface unit) and an IP communication interface unit 172 (second IP communication interface unit). And a storage unit 173 and a relay processing unit 174.

  When the management server 13 transmits a message to the WAN terminals # 1 (14a) and #n (14b), the RAW socket IP communication interface unit 171 is not addressed to the relay device by a RAW socket set as a gateway by the management server 13. That is, all messages are received. The IP communication interface unit 172 is assigned a fixed IP address when communicating with the WAN terminals # 1 (14a) and #n (14b). Note that the storage unit 173 includes virtual IP addresses associated with WAN terminals # 1 (14a) and #n (14b) that are dynamically changed, or that are associated with telegrams that are periodically transmitted. An address table composed of WAN terminal IP addresses is stored.

  When the relay processing unit 174 transmits a message from the management server 13 to the WAN terminals # 1 (14a) and #n (14b), when the RAW socket IP communication interface unit 171 receives the message from the management server 13, the relay processing unit 174 Based on the destination virtual IP address, the address table of the storage unit 173 is referred to obtain the IP address of the corresponding WAN terminal, set as the destination, and the WAN terminal # 1 (14a) via the IP communication interface unit 172, Or it transmits to WAN terminal #n (14b). On the other hand, when a message is transmitted from the WAN terminals # 1 (14a) and #n (14b) to the management server 13, the IP communication interface unit 172 receives a message from the WAN terminals # 1 (14a) and #n (14b). The corresponding virtual IP address is obtained by referring to the address table of the storage unit 173 based on the IP address of the WAN terminal that is the source of the message, and the RAW socket IP communication interface unit 171 is set with the virtual IP address as the destination. To the management server 13 via

  Next, the internal configuration of the management server 13 in FIG. 1 will be described with reference to FIG. 3, and the internal configuration of the wide area network terminal 14 will be described with reference to FIG. As shown in FIG. 3, the management server 13 includes a terminal management unit 131, an IP communication interface unit 132, and a storage unit 133. The terminal management unit 131 generates a request message for controlling a terminal to be managed, such as blocking or returning, and the LAN terminals # 1 (11a) to #n (11d) or WAN terminal # to be managed here. 1 (14a) and #n (14b). Also, the terminal management unit 131 sets the RAW socket IP communication interface unit of the relay device 17 as a gateway for the wide area segment 20 and sets virtual IP addresses for the WAN terminals # 1 (14a) and #n (14b). Send a message to the address.

  The IP communication interface unit 132 is an interface for transmitting / receiving a message to / from the relay device 17 and is assigned a fixed IP address. The storage unit 133 stores a terminal ID and a virtual IP address for individual identification in pairs.

  As shown in FIG. 4, the wide area network terminal 14 (for example, WAN terminal # 1 (14a)) includes a terminal main body 141, an IP communication interface 142, and a storage 143. The terminal body 141 generates meter reading data and transmits a message to the management server 13 via the IP communication interface 142. The storage unit 143 stores a fixed virtual IP address.

(Operation of the embodiment)
Hereinafter, the operation of the communication network system 1 according to the present embodiment will be described in detail with reference to the sequence diagram of FIG. In FIG. 5, first, each of the WAN terminals # 1 (14a) and #n (14b) receives the assigned virtual IP address when the IP address assigned to the terminal dynamically changes or periodically. Transmission is performed from the main body 141 to the relay device 17 via the IP communication interface 142 (step S101). In response, in the relay device 17, the relay processing unit 174 receives via the IP communication interface unit 172, and updates the contents of the address table stored in a partial area of the storage unit 173 (step S102). Here, the address table stores a pair of the virtual IP address associated with the terminal IP address.

  Next, an operation when a request message is transmitted from the management server 13 to the WAN terminal # 1 (14a) or the WAN terminal #n (14b) will be described. The terminal management unit 131 generates a request message, sets the RAW socket IP communication interface unit 171 of the relay device 17 as a gateway for the wide area segment 20, and sets the WAN terminal # 1 (14a) or the WAN terminal #n ( 14b), the generated request message addressed to the virtual IP address is transmitted via the IP communication interface unit 132 (step S111).

  The relay device 17 includes a RAW socket IP communication interface unit 171 to operate as a gateway from the management server 13. Here, the relay device 17 receives all the messages addressed to the WAN terminal # 1 (14a) or WAN terminal #n (14b) by so-called sniffing by the RAW socket IP communication interface unit 171. (Step S112). It is a well-known matter that sniffing is possible by setting a RAW socket. In addition, the relay device 17 includes an IP communication interface unit 172 to which a fixed IP address is assigned in order to communicate with the WAN terminal # 1 (14a) or the WAN terminal #n (14b). The relay processing unit 174 refers to the address table of the storage unit 173 using the virtual IP address that is the transmission destination of the request message received from the management server 13 as a key, reads the actual terminal IP address from this address table, and stores this as the destination Then, the content of the IP header is replaced (step S113) and transmitted from the IP communication interface unit 172 (step S114).

  Subsequently, in the WAN terminal # 1 (14a) or the WAN terminal #n (14b) that has received the request message via the IP communication interface unit 142, the terminal body unit 141 performs control such as blocking and restoration according to the request message. Do.

  Next, the operation when a meter reading message is transmitted from the WAN terminal # 1 (14a) or the WAN terminal #n (14b) to the management server 13 will be described. In WAN terminals # 1 (14a) and #n (14b), an IP address fixedly assigned to the IP communication interface unit 172 of the relay device 17 is registered in advance, and a meter reading message is transmitted to the management server 13. When doing so, it shall transmit to the IP communication interface part 172 of the relay apparatus 17 (step S121).

  The relay device 17 that has received the meter-reading message from the WAN terminal # 1 (14a) or the WAN terminal #n (14b) via the IP communication interface unit 172 is the relay processing unit 174, and the WAN terminal # 1 (14a) that is the transmission source Or by referring to the address table of the storage unit 173 using the terminal IP address of the WAN terminal #n (14b) as a key, and replacing the contents of the IP header so as to set the obtained virtual IP address as the transmission source of the meter reading message (step) S122), and transmits to the IP communication interface unit 132 of the management server 13 via the RAW socket IP communication interface unit 171 (step S123). As a result, the management server 13 can collect meter reading data from the WAN terminals # 1 (14a) and #n (14b) by the terminal management unit 131.

(Effect of embodiment)
As described above, according to the communication network system 1 according to the present embodiment, between the existing first network segment (local area segment 10) and the newly installed second network segment (wide area segment 20). A virtual IP address as a part of the first network segment (local area segment 10) is assigned an IP address to which the connected relay device 17 is dynamically assigned to the second terminal group (wide area network terminal 14). The message transmitted and received between the management server 13 and the second terminal group (wide area network terminal 14) is relayed. A second network segment (wide area segment) in which an IP address is dynamically assigned to the first network segment (local area segment 10) constructed on the assumption that a fixed IP address is assigned by the relay device 17. When incorporating 20), it is possible to provide the communication network system 1 that eliminates the need for modification of existing facilities and thus realizes applications such as meter reading at a low cost without any modification risk. Further, since no modification of equipment is required, an increase in communication traffic for dealing with a dynamic IP address on the management server 13 side can be prevented, so that communication cost does not increase.

  Further, since the communication between the management server 13 and the second terminal group (wide area network terminal 14) is relayed by the virtual IP address and the terminal IP address associated by the relay device 17, the management server 13 Therefore, it is not necessary to manage the IP address dynamically assigned to the terminal group (wide area network terminal 14). Therefore, the processing load for the management is reduced and the throughput of the communication network system 1 is improved.

  According to the relay device 17 according to the present embodiment, the relay device 17 is transmitted from the management server 13 to the second terminal group (wide area network terminal 14) by a RAW socket set as a gateway by the management server 13. For example, the management server 13 can relay, for example, a management message such as blocking or returning to all the second terminal groups (wide area network terminals 14) from the management server 13. When the relay device 17 (relay processing unit 174) transmits a message from the management server 13 to the second terminal group (wide area network terminal 14), the first IP communication interface unit (RAW socket IP communication interface). When the electronic message is received from the management server 13 by the unit 171), the IP address of the corresponding terminal is obtained by referring to the storage unit 173 based on the virtual IP address that is the transmission destination of the electronic message, and set as the destination to perform the second IP communication The data is transmitted to the second terminal group (wide area network terminal 14) via the interface unit (IP communication interface unit 172). Further, when the relay device 17 (relay processing unit 174) transmits a message from the second terminal group (wide area network terminal 14) to the management server 13, the second communication interface unit (IP communication interface unit 172). When the electronic message is received from the second terminal group (wide area network terminal 14), the corresponding virtual IP address is obtained by referring to the storage unit 173 based on the IP address of the terminal that is the transmission source of the electronic message. The address is set as a destination and transmitted to the management server 13 via the first IP communication interface unit (RAW socket IP communication interface unit 171). For this reason, between the local area segment 10 constructed on the assumption that a fixed IP address is allocated and the second terminal group (wide area network terminal 14) to which the IP address is dynamically allocated, There is no load on the management server 13, and mutual communication such as a request message such as shut-off or restoration, a meter reading message, and the like becomes possible.

  Note that, for example, as shown in FIG. 1, the relay processing program according to the present embodiment is configured such that a first terminal group (local area network terminal 11) to which a fixed IP address is assigned is connected to a first communication network (LAN 12). ) Through the first network segment (local area segment 10) connected to the management server 13 and the second group of terminals (wide area network terminal 14) to which the IP address is dynamically allocated is the second communication. In a communication network system 1 including a second network segment (wide area segment 20) connected to the management server 13 via a network (IP network 16), the first network segment (local area segment) is executed by a computer. 10) and the second network A relay processing program used in the relay device 17 connected between the workpiece segment (wide area segment 20). For example, the relay processing program is allocated and stored in a partial area of the storage unit 173 included in the relay device 17, and the relay processing unit 174 functioning as a computer sequentially reads and executes the relay processing program. For example, as shown in FIG. 5, an IP address dynamically assigned to the second terminal group (wide area network terminal 14) is set as a part of the first network segment (local area segment 10). Replacement with the virtual IP address is executed to relay a message transmitted and received between the management server 13 and the second terminal group (wide area network terminal 14) (S111 to S114, S121 to S123).

  According to the relay processing program according to the present embodiment, a new configuration in which an IP address is dynamically assigned to an existing first network segment (local area segment 10) constructed on the assumption that a fixed IP address is assigned. When incorporating the second network segment (wide area segment 20), the relay device 17 that does not require modification of the existing equipment and can realize an application such as meter reading at a low cost without any modification risk, In addition, the communication network system 1 can be provided.

  As mentioned above, although preferred embodiment of this invention was explained in full detail, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Communication network system, 10 ... Local area segment (1st network segment), 11 ... Local area network terminal (LAN terminal # 1- # n: 1st terminal group), 12. ..LAN (first communication network), 13... Management server, 14... Wide area network terminals (WAN terminals # 1 to #N: second terminal group), 15a15b. ... IP network (second communication network), 17 ... relay device, 20 ... wide area segment (second network segment), 171 ... RAW socket IP communication interface unit (first IP) Communication interface unit), 172... IP communication interface unit (second communication interface unit), 173... Storage unit, 174 ... relay processing unit

Claims (2)

A first network segment in which a first terminal group to which a fixed IP address is assigned is connected to a management server via a first communication network;
A second network segment in which a second terminal group to which the IP address is dynamically assigned is connected to the management server via a second communication network;
An IP address dynamically assigned to the second terminal group by a relay device connecting a relay device between the first network segment and the second network segment is a part of the first network segment. A communication network system that relays a message transmitted and received between the management server and the second terminal group, replacing the virtual IP address as
The relay device includes: a first IP communication interface unit that receives a message that is not transmitted to itself by a RAW socket set as a gateway when the management server transmits a message to the second terminal group;
Second IP communication to which a fixed IP address is assigned when communicating with the second terminal group
An interface part;
A storage unit that stores the associated virtual IP address and the IP address of the terminal; and when the telegram is transmitted from the management server to the second terminal group, the management is performed by the first IP communication interface unit. When the message is received from the server, the second IP communication interface unit is obtained by referring to the storage unit based on the virtual IP address that is the transmission destination of the message, obtaining a corresponding terminal IP address, and setting it as a destination When the electronic message is transmitted from the second terminal group to the management server, the electronic message is received from the second terminal group by the second communication interface unit. The corresponding virtual IP address is obtained by referring to the storage unit based on the IP address of the terminal that is the transmission source of the message, and the virtual IP address is set as the destination. And a relay processing unit that transmits to the management server via the first IP communication interface unit. A first network segment in which a first terminal group to which a fixed IP address is assigned is connected to a management server via a first communication network;
A second network segment in which a second terminal group to which the IP address is dynamically assigned is connected to the management server via a second communication network;
An IP address dynamically assigned to the second terminal group by a relay device connected between the first network segment and the second network segment is set as a part of the first network segment. In a relay device comprising a control means for replacing a virtual IP address and relaying a message transmitted and received between the management server and the second terminal group ,
The control means includes
A first IP communication interface unit that receives a message that is not addressed to the relay device by a RAW socket set as a gateway by the management server when the management server transmits a message to the second terminal group; A second IP communication interface unit to which a fixed IP address is assigned when communicating with the terminal group;
When the IP address assigned to the second terminal group changes dynamically, or the IP address of the terminal and the virtual IP address associated with each other by a message transmitted periodically from the second terminal group are stored And when the telegram is transmitted from the management server to the second terminal group, when the telegram is received from the management server by the first IP communication interface unit, the virtual destination that is the destination of the telegram The IP address of the corresponding terminal is obtained by referring to the storage unit based on the IP address, set as a destination, transmitted to the second terminal group via the second IP communication interface unit, and the second terminal group. When transmitting a message from the terminal group to the management server, when the second communication interface unit receives the message from the second terminal group, the message is transmitted from the terminal group. Relay that refers to the storage unit based on the IP address of the terminal, obtains a corresponding virtual IP address, sets the virtual IP address as a destination, and transmits the destination to the management server via the first IP communication interface unit A relay device comprising a processing unit.

Images