JP2006195690A - Communication terminal device and data communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable continuous two-way communication between a center device and a communication terminal device by means of an IP communication network. <P>SOLUTION: The communication terminal device, when powered on or reset, makes a session start request to the center computer. The center computer responds to the request by establishing a session. When a fixed time passes after the start request, the communication terminal device makes a session maintenance request to the center computer. The center computer responds to the request. The session is maintained continuously to allow not only the communication terminal device to send data but also the center computer to send data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data communication system by a communication terminal device that performs meter reading information such as gas and water, security reports, etc. to a center device through an IP (Internet Protocol) communication network such as the Internet.

  In a data communication system that performs automatic meter reading and security notification, bidirectional data communication is performed between the center device and the communication terminal device on the terminal side. When an IP communication network such as the Internet is used as the communication line, the communication terminal device as a client can access the center device as a server, but the center device cannot access the communication terminal device.

  Therefore, in order to ensure the bidirectionality of data communication by the IP communication network, a dynamic DNS (Domain Plugin) is used by using a VPN (Virtual Private Network) or a UPnP (Universal Plug and Play) function of a terminal side router. Name System) had to be used.

Further, as in Patent Document 1, the communication terminal device connects to the terminal device on the center side at a predetermined time interval, and when there is data to be transmitted, transmits the data at the time of connection and establishes the connection. Disconnect. And when predetermined time passes, a communication terminal device will perform a connection again.
JP 2003-244244 A

  When using the VPN as described above, a VPN dedicated device must be provided or a VPN function must be added to the router by software, which increases the cost of the system. When the UPnP function of the terminal side router is used, the router needs to support UPnP, and a dynamic DNS server is also required, and the system that can be operated is limited, and lacks versatility.

  Further, in Patent Document 1, bidirectional communication is possible at regular intervals. However, since there is a period during which communication is not possible, it is not possible to respond immediately when urgent data transmission is required.

  In view of the above, an object of the present invention is to provide a data communication system using an IP communication network that always enables bidirectional communication.

  The present invention relates to a communication terminal device that is connected to a terminal device such as a meter or security device that collects various information, performs data communication with a center device through an IP communication network, and transmits the information to the center device. In addition, the apparatus includes a start unit that makes a session connection request to the center apparatus, and a maintaining unit that maintains the session when the session is established.

  By making a session connection request from the communication terminal device, a session with the center device is established. And a session is maintained by transmitting data so that a session may be maintained from a communication terminal device. If the session is maintained, the two-way communication can always be performed, and the center device can transmit data to the communication terminal device.

  Here, the start means makes a connection request when the power is turned on, or when the IP communication network is restored to the link connection state after the link is disconnected. As a result, the communication terminal device always operates to connect a session with the center device when activated. Therefore, it is possible to automatically enable bidirectional communication as the communication terminal device starts operation.

  At this time, the start unit makes a connection request at a timing specific to the communication terminal device. That is, when there are a plurality of communication terminal devices, each communication terminal device has unique identification information. When each communication terminal device makes a session connection request to one center device, the session connection request is made at a timing determined based on the identification information. Therefore, the connection request timing of each communication terminal apparatus is different. For example, when the communication terminal devices are recovered from a power outage, etc., and all the communication terminal devices are activated at the same time, session connection requests are made at the same time, but since the timing is different, communication from each communication terminal device to the center device is not possible. There is no congestion, and a session with the center device is established reliably.

  The maintaining means periodically transmits data for maintaining the session to the center apparatus. That is, after making a session connection request, data for maintaining a session is transmitted after a predetermined time has elapsed. In this way, by performing communication at a constant timing, it is possible to prevent the session from being disconnected due to a time-out and always maintain a bidirectionally communicable state.

  The communication terminal device transmits data to maintain the session, but when there is no response from the center device, the communication terminal device recognizes that the session has been disconnected due to a stop of the center device, an abnormality in the IP communication network, or the like. Therefore, when the session is disconnected, the start unit makes a connection request in accordance with the timing of data transmission by the maintaining unit. Therefore, even if the session is disconnected, the session is automatically reconnected.

  In addition, when a session with the center apparatus becomes unable to be connected, a connection switching unit that makes a session connection request to the second center apparatus is provided. Usually, in a data communication system, a second center device is provided for backup of a main center device. Even if an abnormal situation occurs in which the session cannot be connected due to a failure of the center device or the like, the session can be kept connected to the center side by making a session connection request to the second center device. There is no inconvenience.

  The connection switching means connects the session from the second center apparatus to the original center apparatus when there is a terminal call request from the terminal device while the session with the second center apparatus is established. Try again. When performing data communication in this way, the session can be automatically replaced from the second center device to the original center device. In addition, when a session is established with the second center device and there is a switching request from the second center device, the session is reconnected from the second center device to the original center device. As a result, when the center device is restored, the session is quickly replaced from the second center device to the original center device, and normal data communication can be performed.

  According to the present invention, by connecting a session from a communication terminal device and maintaining the session, communication is possible at any time, and bidirectional communication can be performed between the center device and the communication terminal device. Therefore, in a data communication system using an IP communication network, bidirectional communication can be easily realized without using VPN or using a device such as a UPnP compatible router or a dynamic DNS server.

  A data communication system of this embodiment is shown in FIG. 1 is a center computer, 2 is a hub, 3 is a center side router, 4 is the Internet, 5 is a terminal side router, 6 is a hub, 7 is a communication terminal device, 8 is a meter, and 9 is a security device.

  In this data communication system, a center-side center computer (center device) 1 and a terminal-side communication terminal device 7 installed in a residence or the like can communicate bidirectionally through an IP communication network such as the Internet 4. The center side router 3 and the terminal side router 5 are connected to the IP communication network by a communication line which is always connected such as an optical fiber, ADSL, and CATV. Note that the communication terminal device 7 may be directly connected to the router 5.

  The communication terminal device 7 transmits meter reading information collected by a meter 8 such as gas or water to the center computer 1 in response to a terminal call or a request from the center computer 1. Further, the communication terminal device 7 transmits the abnormality detection information collected by the security device 9 such as a sensor and a detection switch to the center computer 1 when an abnormal situation occurs.

  As illustrated in FIG. 2, the communication terminal device 7 includes a network connection unit 10, a network I / F 11, a control unit 12, a terminal device I / F 13, a terminal device connection unit 14, a storage unit 15, and a nonvolatile storage unit 16. ing. Terminal devices such as the meter 8 and the security device 9 are connected to the terminal device connection unit 14 via a communication cable. A hub 6 is connected to the network connection unit 10 via a LAN cable, and is connected to a network such as an Ethernet (registered trademark) formed by the router 5 and the hub 6.

  The control unit 12 composed of a microcomputer has start means for making a session connection request to the center computer 1 and maintenance means for maintaining the session when the session is established. These means are executed by software, Communication is possible. Thereby, not only data communication by terminal call from the communication terminal device 7 but also data communication by center polling from the center computer 1 can be performed.

  Then, the control unit 12 creates a packet by attaching a header to the data based on information stored in the non-volatile storage unit 16 according to a predetermined protocol for data communication through the IP communication network. 1 to send. The non-volatile storage unit 16 such as a flash memory stores information necessary for communication such as a terminal device ID, a transmission destination IP address, and a transmission destination port number. The terminal device ID is an IP address or a MAC address. Similarly, the center computer 1 performs data communication. At this time, the transport layer protocol of the center computer 1 and the communication terminal device 7 may be UDP or TCP. In the case of TCP, HTTP may be used as a higher-level protocol. Moreover, you may encrypt each packet as needed.

  In the case of a terminal call, the control unit 12 recognizes when an activation signal from a terminal device such as the meter 8 is input through the terminal device I / F 13, recognizes this, and transmits a terminal device ID, a transmission destination IP address, and a transmission destination. A predetermined transmission code including a port number, a transmission source port number, and the like is created, attached to data as a header, and a packet is created. The packet is transmitted from the network I / F 11 and transmitted to the center computer 1 through the router 5.

  In the case of center polling by the center computer 1, when the control unit 12 receives a packet from the center computer 1 through the Ethernet I / F 11, the data in the packet is sent to the meter 8 or the security device 9 designated through the terminal device I / F 13. Send.

  Here, an operation when the terminal communication device 7 connects and maintains a session with the center computer 1 will be described. As shown in FIG. 3, when the power of the communication terminal device 7 is turned on or reset, the control unit 12 initializes and automatically sets an IP address by DHCP as necessary, and then performs a session. A packet having the start request message as data is transmitted to the center computer 1. When the center computer 1 receives this message, the center computer 1 transmits a packet having the session start response message as data to the communication terminal device 7. When the session is established in this way, bidirectional communication can be performed between the communication terminal device 7 and the center computer 1.

  If communication is not performed for a predetermined time after the session is established, the session is disconnected due to timeout. Therefore, the control unit 12 transmits a packet having data as a session maintenance request message for maintaining a session to the center computer 1 at regular intervals. In addition, this fixed time is set to a time shorter than a predetermined time for timeout. When the center computer 1 receives this message, the center computer 1 transmits a packet having the session maintenance response message as data to the communication terminal device 7. This session maintenance request message is periodically transmitted to maintain the session.

  Since the IP address of the terminal communication device 7 is a private IP address, it is usually impossible to access the communication terminal device 7 from the center computer 1 and directly transmit data. However, since the session is maintained as described above, data transmission from the center computer 1 is always possible.

  By the way, after the session starts, when the terminal-side hub 6 is stopped or the LAN cable is disconnected, the network I / F 11 notifies the control unit 12 of the link disconnection state. The network I / F 11 transmits / receives link pulses to / from the router 5 and the hub 6 in the network at a constant cycle, and can detect the link state based on the presence / absence of the link pulse. When the link is disconnected, the communication terminal device 7 cannot communicate with the center computer 1. When the hub 6 and the LAN cable are restored, the link status is notified from the network I / F 11 to the control unit 12. The control unit 12 immediately transmits a session start request message similarly to when the power is turned on. Since the session is started and maintained, the communication terminal device 7 can communicate with the center computer 1 in both directions.

  Further, when the center computer 1 is stopped, the routers 3 and 5 are stopped, the center computer 1 and the communication terminal device 7 cannot communicate with each other, but the center computer 1 and the communication terminal device 7 cannot recognize this. As shown in FIG. 4, after the session is started, a session maintenance request and response are transmitted and received at regular intervals. As a result, the center computer 1 ends the session if there is no session maintenance request even after a predetermined time has elapsed. If there is no maintenance response to the session maintenance request, communication terminal apparatus 7 ends the session.

  When the session is thus terminated, the communication terminal device 7 connects the session again. That is, a session start request message is transmitted instead of the maintenance request at the timing of making a periodic session maintenance request. When a session start response is received from the center computer 1, the session is started as usual. Thereafter, a session maintenance request message is periodically transmitted to maintain the session.

  As described above, when the communication terminal device 7 starts connection of a session to the center computer 1, if the center computer 1 is still stopped, there is no start response to the session start request and connection of the session cannot be started. Here, the center side usually includes a second center computer for backup. Utilizing this, when the communication terminal device 7 cannot connect the session with the center computer, the communication terminal device 7 connects the session with the second center computer. That is, the control unit 12 includes a connection switching unit that makes a session connection request to the second center computer when a session with the center computer 1 is not connectable.

  As shown in FIG. 5, the control unit 12 of the communication terminal device 7 determines that connection is not possible when there is no session maintenance response or start response from the center computer 1. Then, a session start request message is transmitted to the second center computer based on the IP address and port number of the second center computer stored in the nonvolatile storage unit 16. When a session start response is received from the second center computer, the session is started as usual. Thereafter, a session maintenance request message is periodically transmitted to the second center computer to maintain the session. As a result, even if the center computer 1 fails and stops, a system that does not stop as a communication system can be realized.

  The timing for making a session connection request to the second center computer is performed when it is detected from the center computer 1 that there is no session maintenance response or start response. In this way, even if the session with the center computer 1 is disconnected, the session is connected to the second center computer, so that the session with the center side is always disconnected without being disconnected. Become.

  When the session with the second center computer is connected, the control unit 12 receives the activation signal from the terminal device through the terminal device I / F 13 and recognizes that the request is for the terminal call. Reconnect the session from the center computer to the original center computer 1. That is, the control unit 12 transmits a session start request message to the center computer 1. When a session with the center computer 1 is connected, the control unit 12 disconnects the session with the second center computer and performs data communication with the center computer 1 with which the session has been established. If the center computer 1 remains stopped, the session is not established, and the control unit 12 performs data communication with the second center computer without disconnecting the session with the second center computer. Thus, the session can be automatically switched from the second center computer to the regular center computer 1.

  In addition, when a session with the second center computer is connected, the control unit 12 connects the session from the second center computer to the original center computer 1 when there is a switching request from the second center computer. cure. That is, as shown in FIG. 6, when the center computer 1 is restored, the second center computer transmits a session switching request message to the communication terminal device 7. Upon receiving this message, the control unit 12 transmits a response message to the second center computer and disconnects the session. Then, a session start request message is transmitted to the center computer 1. The center computer 1 responds and a session with the center computer 1 is connected. Thereafter, the session is similarly maintained. As a result, the session can be quickly switched from the second center computer to the regular center computer 1.

  In the above data communication system, in general, a plurality of communication terminal apparatuses 7 are provided instead of one, and are connected to the router 5 and the hub 6. Different IDs are set for the respective communication terminal devices 7. Each communication terminal device 7 has a unique MAC address and serial number. The control unit 12 makes a session connection request at a timing determined based on the unique identification information such as the ID and the serial number. That is, when the power is turned on or reset, the control unit 12 starts session connection, but the timing for transmitting the session connection request message is the time determined based on the unique identification information after the power is turned on. When it has passed. Then, after a session is established, a session maintenance request message is transmitted when a predetermined time has elapsed since the first message was transmitted.

  In this way, by shifting the timing of session connection requests for each communication terminal device 7, for example, when a power failure occurs and recovery is performed, each communication terminal device 7 makes a session connection request all at once. However, as described above, since connection request timings are shifted, connection requests from a plurality of communication terminal devices 7 do not overlap. Therefore, since the center computer 1 performs communication for session connection with the plurality of communication terminal devices 7 in order, a large amount of communication processing is not performed at once, and the load on the center computer 1 can be distributed.

  Further, the communication terminal device 7 also makes a session maintenance request after a certain time has elapsed since the connection request was made. Therefore, the timing of the maintenance request of each communication terminal device 7 is shifted, communication with each communication terminal device 7 is not concentrated, and the load on the center computer 1 can be distributed.

  At this time, the maintenance request from the plurality of communication terminal devices 7 may overlap by setting a certain time, which is the timing when the maintenance request is made in each communication terminal device 7, to be different for each communication terminal device 7. However, the timing of the next maintenance request will be off. Therefore, the larger the data communication system provided with a larger number of communication terminal devices 7, the more the load on the center computer 1 can be reduced and the communication quality can be improved.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. When a plurality of communication terminal devices are connected to the router, a plurality of communication terminal devices can simultaneously transmit data to the center computer and data using NAPT (Network Address Port Translation: IP masquerade) that distinguishes each communication terminal device by a port number. Communication may be possible.

Overall configuration diagram of data communication system of the present invention Block diagram showing schematic configuration of communication terminal device Communication sequence diagram when connecting a session Communication sequence diagram when session is disconnected Communication sequence diagram when the session is switched to the original center computer due to the terminal call after the communication terminal device connects the session with the second center computer Communication sequence diagram when the session is switched to the original center computer in response to a switching request from the second center computer after the communication terminal device connects the session with the second center computer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Center computer 2 Hub 3 Center side router 4 Internet 5 Terminal side router 6 Hub 7 Communication terminal device 8 Meter 9 Security apparatus 10 Network connection part 11 Network I / F
12 Control unit 13 Terminal device I / F
14 Terminal device connection unit 15 Storage unit 16 Non-volatile storage unit

Claims (13)

A terminal device that collects various types of information is connected, performs data communication with a center device through an IP communication network, and transmits the information to the center device. A communication terminal apparatus comprising start means for making a connection request and maintenance means for maintaining the session when the session is established. 2. The communication terminal apparatus according to claim 1, wherein the start means makes a connection request when the power is turned on or when the IP communication network recovers to the link connection state after the link is disconnected. 3. The communication terminal apparatus according to claim 2, wherein the start unit makes a connection request at a timing specific to the communication terminal apparatus when the power is turned on or reset. The communication terminal apparatus according to claim 1, wherein the maintaining unit periodically transmits data for maintaining a session to the center apparatus. 5. The communication terminal apparatus according to claim 4, wherein the maintaining means transmits the data for maintaining the session after a predetermined time has elapsed after making the connection request. 6. The communication terminal apparatus according to claim 5, wherein when the session is disconnected, the start unit makes a connection request in accordance with the timing of data transmission by the maintaining unit. The communication terminal device according to claim 1, further comprising a connection switching unit configured to make a connection request to the second center device when a session with the center device becomes impossible to connect. . The connection switching means reconnects the session from the second center apparatus to the original center apparatus when there is a terminal call request from the terminal device while the session with the second center apparatus is established. The communication terminal device according to claim 7. The connection switching means reconnects the session from the second center apparatus to the original center apparatus when there is a switching request from the second center apparatus when a session with the second center apparatus is established. The communication terminal device according to claim 7. A communication terminal device connected to a terminal device that collects various types of information and a center device perform data communication through an IP communication network, and the communication terminal device transmits the information to the center device. The communication terminal device makes a session connection request to the center device, and when the session is established, transmits data for maintaining the session to the center device and maintains the session. Communications system. A plurality of communication terminal devices make a session connection request to one center device, and each communication terminal device has unique identification information, and a session connection request at a timing determined based on the identification information. The data communication system according to claim 10, wherein: 12. The data communication system according to claim 10, wherein the communication terminal device establishes a session with the second center device and maintains the session when the session with the center device becomes inaccessible. . When a session with the second center apparatus is connected, a session with the center apparatus becomes connectable, or when a terminal call request is received from the terminal device, the communication terminal apparatus 13. The data communication system according to claim 12, wherein the session is reconnected from the center device of 2 to the original center device.

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