Patent Publication Number: US-2009219949-A1

Title: Connection adapter for communication device

Description:
TECHNICAL FIELD 
     The present invention relates to the field of telemetering used in such purposes as the collection of sales information from vending machines and to the field of telematics used in delivering traffic information to mobile objects and like purposes. 
     BACKGROUND ART 
     Recently, telemetering and telematics for collecting and distributing information over a wireless packet communication network have become widespread. The telemetering originally is a generic term which refers to a system of reading a measured value by a measure via a communication line. However, it has been generally used as a term indicating not only reading data but also monitoring the operation of equipment and performing remote control. A typical example of telemetering is a sales management system of vending machines, a use amount management system of gas, water supply, etc., or a management system in a parking lot without human attendant, etc. For a sales management system of vending machines, refer to the patent document 1. The telematics refers to providing information in real time by combining a mobile object such as an automobile with a communication system. A typical example of telematics is a vehicle-mounted information system etc. for providing in real time a terminal provided for a vehicle with traffic information and navigation information. 
     In the fields above, communication equipment for connection to a wireless packet communication network in a remote location and a host device using the communication equipment are arranged. The host device corresponds to Data Terminal Equipment (DTE). The communication equipment corresponds to Data Circuit-terminating Equipment (DCE). 
     For example, in the sales management system of vending machines, the control device for controlling the sales and the temperature in the machine corresponds to the host device. Each host device is periodically or arbitrarily connected to a predetermined network through communication equipment, and to a predetermined managing computer over the network. The host device connected to the managing computer transmits various types of data to be managed. 
     Patent Document 1: Japanese Patent Publication No. 2003-51056 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in the conventional system, when communications are started from a managing computer to a host device, a long time may be required before starting the communications or a connection may not be successfully made. 
     For an example, a conventional flow rate monitor system for a sewage system is described below. In this system, a TCP/IP is used as a communication protocol between a host device and a managing computer. The managing computer transmits a communication start TCP packet addressed to the host device to the wireless packet communication network to start communication with the host device. The wireless packet communication network refers to the destination address of the communication start TCP packet, and notifies the host device corresponding to the destination address of a message. The message is notified through a messaging service provided by the wireless packet communication network. The host device receives the message and performs a connection to the wireless packet communication network. 
     The notifying process for the message and the connecting process to the wireless packet communication network can require few to a dozen seconds. Therefore, a communication start TCP packet first transmitted from the managing computer is discarded due to time-out, and the managing computer attempts retransmission of the communication start TCP packet several times. That is, the communication start TCP packet actually received by the host device is received after several retransmissions. The retransmission interval of a TCP packet is generally set longer each time the retransmission is repeated. For example, the retransmission intervals are set to 3 seconds, 6 seconds, and 12 seconds. Therefore, there can be a case in which several seconds are required to perform retransmission of a communication start TCP packet although the connecting process to the wireless packet communication network has been completed. In addition, the retransmission frequency of a TCP can reach the upper limit until the connecting process is completed, thereby failing in establishing a TCP connection. 
     The present invention has been mode to consider the above-mentioned problems, and has an object of shortening the processing time from a communication start request to a start of the communication. 
     Means for Solving the Problems 
     To attain the above-mentioned object, the present application propose a connection adapter for communication device including: a first interface for connection to communication equipment for a wireless packet communication network; a second interface for connection to a host device for performing communications using a TCP/IP through the communication equipment; a line control unit for controlling a line between the host device and the wireless packet communication network; and a communication control unit for relaying the communication by the host device using the communication equipment. The connection adapter for communication device is characterized in that: upon receipt of a communication start TCP packet addressed to the host device from the wireless packet communication network after the establishment of the connection to the wireless packet communication network, the line control unit (a) temporarily stores the communication start TCP packet in predetermined storage means, (b) notifies the host device of the reception, (c) performs a response process on behalf of the wireless packet communication network in response to the connecting process to be started by the host device, and (d) transmits the communication start TCP packet stored in the storage means to the host device when the connecting process by the host device is completed. 
     In the present invention, the host device performs a connection to the wireless packet communication network through the connection adapter. Upon receipt of a communication start TCP packet from the wireless packet communication network after a connection to the wireless packet communication network is established, the connection adapter temporarily stores the TCP packet, and starts a connecting process to the host device. When the connection adapter completes the connecting process, the device transmits the temporarily stored communication start TCP packet to the host device without delay. Therefore, even if the retransmission interval between a communication start TCP packet received by the connection adapter and a next communication start TCP packet is long, the host device receives the communication start TCP packet upon completion of the preparation for the communication, thereby successfully shortening the time to the start of communications. 
     The connecting process to the wireless packet communication network by the connection adapter is performed in, for example, the following cases. That is, when the connection adapter receives a message from the messaging service in the wireless packet communication network, the source of the message is designated from the message, and the connecting process to the wireless packet communication network is started so as to allow communications with the source. The communication start TCP packet is formed by a TCP packet having a SYN flag turned ON and an ACK flag OFF of the TCP header. 
     Advantages of the Invention 
     As described above, according to the present invention, even if the retransmission interval between the communication start TCP packet received by the connection adapter and the next communication start TCP packet is long, the host device can receive the communication start TCP packet upon completion of the preparation for communications, thereby shortening the time to the start of the communications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the configuration of a communication system; 
         FIG. 2  shows a network upon which a host device etc is based; 
         FIG. 3  is an explanatory view of an example of address management table; 
         FIG. 4  shows a network of a system according to an embodiment of the present invention; 
         FIG. 5  shows the configuration of a connection adapter; 
         FIG. 6  is a block diagram showing the function of a main control unit of a connection adapter; 
         FIG. 7  is an explanatory view of an example of the setting information in the connection adapter; 
         FIG. 8  is an explanatory view of the sequence of using a network connection service as a presumption and starting communications from a host device; 
         FIG. 9  is an explanatory view of the sequence of using a network connection service as a presumption and starting communications from a managing computer; 
         FIG. 10  is an explanatory view of the sequence of starting communications from a host device according to an embodiment of the present invention; 
         FIG. 11  is an explanatory view of the address converting process; 
         FIG. 12  is an explanatory view of the sequence of starting communications from a managing computer according to an embodiment of the present invention; 
         FIG. 13  is an explanatory view of the sequence of starting communications from a managing computer according to an embodiment of the present invention; and 
         FIG. 14  is an explanatory view of an address converting process. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
           1  . . . connection adapter for communication device,  120  . . . main control unit,  121  . . . line control unit,  122  . . . communication control unit,  10 ,  11  . . . host device,  20 ,  25 ,  26  . . . communication module,  40 ,  45 ,  46  . . . wireless packet communication network,  42  . . . messaging server,  43  . . . address management server,  50  . . . in-house LAN,  51 ,  52  . . . managing computer,  60  . . . network router,  63  . . . line control unit,  64  . . . communication control unit,  65  . . . setting data storage unit,  65   a  . . . host device information table,  65   b  . . . address conversion table 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The communication system according to an embodiment of the present invention is described below with reference to the drawings.  FIG. 1  shows the configuration of a telemetering system using the communication system according to the present invention. 
     This system aims at providing a network environment obtained by connecting a host device  10  of, for example, a control device of a vending machine to an in-house LAN  50  over a wireless packet communication network  40  as shown in  FIG. 1 . It is assumed that the host device  10  and a terminal (in the example shown in  FIG. 1 , a managing computer  51  of a vending machine etc.) in the in-house LAN  50  is set for a network connection service for assigning a fixed IP address. The main object of the present system is to allow the wireless packet communication network  40  to use a network connection service for assigning a dynamic IP address to a connection terminal without reforming a terminal in the host device  10  and the in-house LAN  50 . To solve the problem, the present system realizes the following two points. That is, (a) a terminal in the in-house LAN  50  can start communications to the host device  10 , and (b) in the communications started by the host device  10 , the host device  10  can be identified. The communication system is described below in detail. 
     The host device  10  corresponds to Data Terminal Equipment (DTE). The host device  10  is designed to correspond to a specific carrier and a network connection service provided by the carrier. Specifically, it is assumed that the host device  10  uses a network connection service of assigning a fixed IP address to a connection terminal. In addition, the host device  10  is designed to connect a communication module corresponding to the service, and correspond to a connection protocol, an authentication protocol, etc. corresponding to the service. 
     The network connection service upon which the host device  10  is based is described below. In the network connection service, a telephone number is assigned to a communication module in advance by a carrier. In the wireless packet communication network provided by the network connection service is provided with a relay device for performing line control, packet relay, etc. In the relay device, a telephone number is assigned to an in-house LAN which is a connection destination network. Upon issue of a call to the telephone number of the relay device in the wireless packet communication network, a terminal having connected communication module makes a connection to a predetermined network such as an in-house LAN. A connection to the relay device is allowed only from a communication module having a telephone number assigned in advance. 
       FIG. 2  shows an example of a network using a network connection service upon which the host device  10  is based. As shown in  FIG. 2 , the host device  10  performs a connection to wireless packet communication networks  45  and  46  configured by the network connection service using communication modules  25  and  26 . In the present embodiment, the wireless packet communication network  45  and the communication module  25  are assumed to be in accordance with the PDC standard. The wireless packet communication network  46  and the communication module  26  are assumed to be in accordance with the PHS standard. Furthermore, in the service, an IP address belonging to the network of 192.168.0.0/28 is fixedly assigned to the WAN side interface of a network router  60  and the communication module  25 . The host device  10  is connected to the LAN  50  in the terminal type network connection service. Therefore, the IP address assigned to the communication modules  25  and  26  is synonymy to the IP address assigned to the host device  10 . It is assumed that, in the in-house LAN  50 , a fixed IP address of each device is assigned so that it can belong to the network of 192.168.9.0/24. Upon receipt of a packet with an IP address in the 192.168.0.0/28 from the in-house LAN  50 , the network router  60  relays the packet to the wireless packet communication networks  45  and  46 . On the other hand, upon receipt of a packet with an IP address in the 192.168.9.0/24 from the wireless packet communication networks  45  and  46 , the network router  60  relays the packet to the in-house LAN  50 . With the configuration, the managing computer  51  can start communications to a fixed IP address of the host device  10 . In addition, the managing computer  51  can identify the host device  10  with reference to the source IP address of the communication from the host device  10 . 
     The present invention is based on the use of the host device  10  and the managing computer  51  as they are, and it is assumed that a network system can be configured in the wireless packet communication network  40  provided by the network connection service in which a dynamic IP can be assigned. 
     Next, a network connection service used in an embodiment of the present invention, and in which a dynamic IP address is assigned is described below. In the network connection service, a telephone number is assigned in advance by a carrier to a communication module  20 . The wireless packet communication network  40  is provided with a relay device  41  for controlling a line and relaying a packet etc, as shown in  FIG. 1 . A terminal to which the communication module  20  is connected is connected to the wireless packet communication network  40  by issuing a call with a predetermined special number assigned. Then, the terminal can be connected to the in-house LAN  50  which is a connection destination network by performing an authenticating process using a PAP (Password Authentication Protocol) with the relay device  41 . In the above-mentioned PAP authentication, a connection destination network can be specified by including the information specifying a connection destination in a user name. In the network connection service, an IP address group in a predetermined range is allocated by a carrier to the wireless packet communication network  40 , and an IP address contained in the IP address group is dynamically assigned by the IPCP (Internet Protocol Control Protocol) to the communication module  20 . 
     An IP address assigned to the communication module  20  is predetermined. As shown in  FIG. 1 , an address management server  43  is provided for the wireless packet communication network  40 . The address management server  43  manages the telephone number of the connection terminal and a list of IP addresses to be distributed to the terminal having the telephone number. Specifically, as shown in  FIG. 3 , the address management server  43  is provided with an address correspondence table  43   a  describing the correspondence between a telephone number and an IP address. In this connection service, the wireless packet communication network  40  acquires the telephone number of the communication module  20  when the communication module  20  is connected. Then, the IP address corresponding to the telephone number is acquired from the address correspondence table  43   a,  and the acquired IP address is distributed to the communication module  20 . An IPCP is used for distributing the address. That is, according to the present embodiment, the dynamic IP assigning technique referred to as an IPCP is used, but the distributed IP address is predetermined. The address management server  43  provides a user with an interface for updating the address correspondence table  43   a.    
     In addition, in this connection service, when the wireless packet communication network  40  receives an IP packet having the IP address corresponding to the terminal from the in-house LAN  50 , and when the terminal is not connected to the wireless packet communication network  40 , a messaging server  42  acquires a telephone number corresponding to the IP packet from the address management server  43 . The wireless packet communication network  40  transmits a message to the telephone number. The messaging service is not a network connection service using a TCP/IP, but is implemented by a unique protocol using a wireless communication network. Thus, the terminal may recognize that there has been a connection request from the in-house LAN  50 . 
     Next, the chart of the network of the system according to an embodiment of the present invention is described below with reference to  FIG. 4 .  FIG. 4  shows the network of the present system. As shown in  FIG. 4 , in this system, as with the network described above with reference to  FIG. 2 , the in-house LAN  50  is assigned a fixed IP address belonging to 192.168.9.0/24. In addition, the host device  10  is assigned a fixed IP address belonging to 192.168.0.0/28. The wireless packet communication network  40  is assigned an address group of 172.16.0.0/28. The WAN side of the network router (hereinafter referred to simply as a “router”)  60  at the boundary point between the wireless packet communication network  40  and the in-house LAN  50  is assigned a fixed IP address 172.16.0.14. The communication module  20  is assigned a dynamic address in 172.16.0.0/28 when it is connected to the wireless packet communication network  40  (in  FIG. 4 , it is expressed by 172.16.0.X for convenience). A connection adapter  1  is connected to the LAN  50  with the terminal type network connection service. Therefore, the IP address of the connection adapter  1  is an IP address dynamically assigned to the communication module  20 . In the present invention, in the above-mentioned network environment, communications can be started from the managing computer  51  in the in-house LAN  50  to the host device  10 , and the host device  10  can be identified when the communications are started from the host device  10  to the managing computer  51 . 
     Next, the connection adapter  1  is described below in detail. The connection adapter  1  connects plural types of host devices  10  corresponding to the Data Terminal Equipment (DTE) to plural types of communication equipment  20 ,  25 , and  26  corresponding to the data circuit-terminating equipment (DCE). The connection adapter  1  according to an embodiment of the present invention corresponds to the communication module  20  in accordance with the CDMA standard, the communication module  25  in accordance with the PDC standard, and the communication module  26  in accordance with the PHS standard. Each of the communication modules  20 ,  25 , and  26  is communication equipment connected to the wireless packet communication network  40 ,  45 , and  46  configured by the respective carriers. Each carrier corresponds to a uniquely determined communication standard and communication protocol service. As described above, the host device  10  is designed to correspond to a specific carrier and a service provided by the carrier. Specifically, a communication module corresponding to the service is connected, and the connection protocol and the authentication protocol can be satisfied corresponding to the service. 
     The host device  10  according to an embodiment of the present invention can be directly connected to the communication module  25  in accordance with the PDC standard, and the communication module  26  in accordance with the PHS standard. Using the communication modules  25  and  26 , it can be connected to the in-house LAN  50  over each of the wireless packet communication networks  45  and  46 . The connection adapter  1  according to an embodiment of the present invention can be connected to the in-house LAN  50  through the wireless packet communication network  40  using the communication module  20  in accordance with the CDMA standard without modifying or changing the host device  10 . The connection adapter  1  is described below in more detail. 
     First, the configuration of the connection adapter  1  according to an embodiment of the present invention is described below with reference to  FIG. 5 .  FIG. 5  shows the state in which the connection adapter  1  includes the three communication modules  20 ,  25 , and  26 . During the operation, at least the communication module  20 ,  25 , or  26  can be included for practical use. 
     The connection adapter  1  includes in a housing  100  a primary control substrate  110 , a secondary control substrate  200  for loading the communication module  25  in accordance with the PDC standard, a secondary control substrate  300  for loading the communication module  20  in accordance with the CDMA standard, and the communication module  26  in accordance with the PHS standard. The secondary control substrates  200  and  300 , and the communication module  26  are provided as freely attached to and detached from the primary control substrate  110 . 
     The connection adapter  1  according to an embodiment of the present invention is provided with plural types of connectors for connection to the host device for connection to plural types of main control units. Specifically, the primary control substrate  110  is provided with a connector  111  used in accordance with the RS-232C standard, a connector  112  used in accordance with the RS-485 standard, and a connector  113  used in accordance with the CAN (Controller Area Network) standard. 
     A primary control substrate  110  is provided with a main control unit  120  implemented by an FPGA (Field Programmable Gate Array) as a type of PLD (Programmable Logic Device), an interface circuit  131  in accordance with the RS-232C standard, an interface circuit  132  in accordance with the RS-485 standard, and an interface circuit  133  in accordance with the CAN standard. Each of the interface circuits  131 ,  132 , and  133  is interposed between the corresponding connectors  111 ,  112 , and  113  and the main control unit  120 , respectively. Thus, the main control unit  120  can communicate with the host device connected to the connectors  111 ,  112 , and  113  through each of the interface circuits  131 ,  132 , and  133 . 
     The primary control substrate  110  includes a connector  141  for connection with the secondary control substrate  200 , a connector  142  for connection with the secondary control substrate  300 , and a connector  143  for connection with the communication module  26  in accordance with the PHS standard. Each of the connectors  141 ,  142 , and  143  is connected to the main control unit  120 . Thus, the main control unit  120  can communicate with the communication module  25  in accordance with the PDC standard through the secondary control substrate  200 . Similarly, the main control unit  120  can communicate with the communication module  20  in accordance with the CDMA standard through the secondary control substrate  300 . The main control unit  120  can communicate directly with the communication module  26  in accordance with the PHS standard. 
     Furthermore, the primary control substrate  110  is provided with EPROM  151  storing a control program of the main control unit  120 , and RAM  152  for use as various work area of the main control unit  120 . Additionally, the primary control substrate  110  is provided with a module selection switch  160  for selection of the communication module  20 ,  25 , or  26 . The main control unit  120  performs an operation corresponding to the communication modules  20 ,  25 , and  26  selected by the module selection switch  160 . The configuration and the operation of the main control unit  120  are described later. 
     The primary control substrate  110  operates by external DC power supply. In addition, the primary control substrate  110  supplies DC power to the secondary control substrates  200  and  800 , and the communication module  26  in accordance with the PHS standard through each of the connectors  141 ,  142 , and  143 . The primary control substrate  110  is provided with a power supply monitor circuit  170  for monitoring external abnormal supply of DC power, and a backup battery  171 . When the power supply monitor circuit  170  detects external abnormal power supply, the circuit controls to supply power from the backup battery  171  to the primary control substrate  110 , the secondary control substrates  200  and  300 , and the communication module  26  in accordance with the PHS standard. In addition, when the power supply monitor circuit  170  detects external abnormal power supply, it notifies the main control unit  120  of the abnormal power supply. Furthermore, when the power supply monitor circuit  170  detects the recovery of external power supply after abnormal power supply, it notifies the main control unit  120  of the recovery. 
     In addition, the primary control substrate  110  is provided with a circuit initializing unit  180  for initializing and generating the internal circuit of the main control unit  120  implemented by the FPGA. The circuit initializing unit  180  contains a program for initializing and generating an internal circuit of the main control unit  120 . The circuit initializing unit  180  forms a circuit configuring the main control unit  120  in the FPGA at an instruction from an externally connected terminal (not shown in the drawings). 
     The secondary control substrate  200  is to connect the primary control substrate  110  to the communication module  25  in accordance with the PDC standard. The secondary control substrate  200  is provided with a connector  201  for connection with the primary control substrate  110 , a connector  202  for connection to a terminal  25   a  of the communication module  25  in accordance with the PDC standard, and an interface circuit  210  for connection between the primary control substrate  110  and the communication module  25 . The interface circuit  210  converts the number of pins between the connector  202  and the connector  201 , converts the assignment of pins, and generates a waveform, etc. The communication module  25  according to an embodiment of the present invention requires a predetermined memory chip storing its own telephone number information etc., and requires a dedicated backup battery. Accordingly, the memory chip  220  and the backup battery  230  are connected to the communication module  25  of the secondary control substrate  200  is connected to the communication module  25  through the connector  202 . The secondary control substrate  200  is operated by a DC power supply from the primary control substrate  110  as described above, and DC power is supplied to the communication module  25  through the connector  202 . An antenna connection terminal  25   b  of the communication module  25  is connected to an antenna connection terminal  191  attached to the housing  100 . 
     The secondary control substrate  300  is to connect the primary control substrate  110  to the communication module  20  in accordance with the CDMA standard. The secondary control substrate  300  is provided with a connector  301  for connection to the primary control substrate  110 , a connector  302  for connection to a terminal  20   a  of the communication module  20  in accordance with the CDMA standard, and an interface circuit  310  for connection between the primary control substrate  110  and the communication module  20 . The interface circuit  310  converts the number of pins between the connector  302  and the connector  301 , converts the assignment of pins, and generates a waveform, etc. In addition, the secondary control substrate  300  is operated by the DC power supply from the primary control substrate  110  as described above, and supplies DC power to the communication module  20  through the connector  302 . An antenna connection terminal  20   b  of the communication module  20  is connected to an antenna connection terminal  192  attached to the housing  100 . 
     A terminal  26   a  of the communication module  26  in accordance with the PHS standard is connected to the connector  143  of the primary control substrate  110 . An antenna connection terminal  26   b  of the communication module  26  is connected to an antenna connection terminal  193  attached to the housing  100 . 
     Next, the configuration and the operation of the main control unit  120  are described below with reference to  FIG. 6 .  FIG. 6  is a block diagram showing the functions of the main control unit  120 . Only the components related to the gist of the present invention are described, and others are omitted. 
     As shown in  FIG. 6 , the main control unit  120  includes a line control unit  121  for controlling the line such as establishing a line connection etc., a communication control unit  122  for controlling data communication on the line established by the line control unit  121 , an interface  123  with the host device  10 , and an interface  124  with the communication modules  20 ,  25 , and  26 . The line control unit  121  controls line connection by an AT command, controls connection of an IP layer by the LCP (link control protocol) and the IPCP, and controls connection of a TCP/UDP layer. The communication control unit  122  performs a converting process of an IP address included in a header of the IP layer in the data communication on the line established by the line control unit  121 . 
     The line control unit  121  and the communication control unit  122  switch the process depending on the communication modules  20 ,  25 , and  26  selected by a module selection switch  160 . In the present embodiment, the host device  10  is designed to directly connect and use the communication modules  25  and  26 . Therefore, when the communication module  25  or  26  is selected by the module selection switch  160 , the line control unit  121  and the communication control unit  122  do not perform a special process on the data between the host device  10  and the communication module  25  or  26 , but only pass the data. On the other hand, when the communication module  20  is selected, the line control unit  121  and the communication control unit  122  perform converting, passing, and discarding processes according to a predetermined rule to data between the host device  10  and the communication module  20 . The data required for the data processing is stored in a set data storage unit  151   a  of the EPROM  151 . 
     The data stored in the set data storage unit  151   a  is described with reference to  FIG. 7 . As shown in  FIG. 7 , the set data storage unit  151   a  stores a call issue command (including a telephone number) for connection to the wireless packet communication network  40 , a fixed IP address of the host device  10 , authentication data required for connection to the wireless packet communication network  40 , and an IP address of the connection destination router  60 . 
     Next, the communication procedure in this system is described below with reference to the attached drawings. First, before the description of the communication system according to an embodiment of the present invention, the communication procedure when using the premise network connection service upon which the host device  10  and the managing computer  51  are based is described below with reference to the attached drawings. As described above, since the host device  10  corresponds to the communication module  25  in accordance with the PDC standard and the first wireless packet communication network  45 , the connection adapter  1  does not perform any process on the data between the host device  10  and the communication module  25 . A similar operation is performed when the host device  10  is connected to the in-house LAN  50  using the communication module  26  in accordance with the PHS standard and the wireless packet communication network  46 . 
     First, the case in which communication is started for the managing computer  51  from the host device  10  is described below with reference to the sequence chart shown in  FIG. 8 . 
     In this example, the following contents are presumed. That is, it is assumed that the telephone number ‘080AABB’ is assigned to the communication module  25  from the carrier. It is assumed that an IP address of 192.168.0.0/28 is distributed from the carrier, and the IP address 192.168.0.1 is assigned to the host device  10  connected to the wireless packet communication network  45  using the communication module  25 . It is assumed that the IP address of the managing computer  51  of the communication partner is 192.168.9.10. The communication module  25  is assumed to be connected to the relay device of the wireless packet communication network  45  by issuing a call at an ‘ATDT’ command to the telephone number ‘080CCDD’. 
     As shown in  FIG. 8 , when the host device  10  issues a ‘ATDT080CCDD’ command to the connection adapter  1  (step S 1 ), the line control unit  121  of the connection adapter  1  transfers the command to the communication module  25  as it is (step S 2 ). The trigger of the issue of the call can be the time when an IP packet of the destination address: 192.168.0.10 is generated. At the AT command, the communication module  25  issues a call to the relay device in the wireless packet communication network  45  (step S 3 ). The relay device confirms the telephone number of the communication module  25  of the source, and rejects the connection from the terminal without a contract (step S 4 ). Upon receipt of the response ‘CONNECT’ indicating that a connection is completed at the line level through the communication module  25  (step S 5 ), the line control unit  121  of the connection adapter  1  transfers the response to the host device  10  (step S 6 ). 
     Next, the host device  10  starts the process to make a connection to the in-house LAN  50  through the wireless packet communication network  45  by the PPP. Specifically, a connection to the relay device of the wireless packet communication network  45  is established at the IP level through the LCP and the IPCP (step S 7  and S 8 ). The line control unit  121  of the connection adapter  1  bidirectionally passes the packet relating to the LCP and the IPCP. Thus, the host device  10  can communicate with the in-house LAN  50  at the IP level. Therefore, the data communication using an upper protocol such as TCP/UDP etc. is started (step S 9 ). The relay device of the wireless packet communication network  45  relays only the IP packet whose destination address or the source IP address is included in the 192.168.0.0/28 (step S 10 ). 
     Next, the case where the communication is started on the host device  10  from the managing computer  51  is described below with reference to the sequence chart shown in  FIG. 9 . 
     When the managing computer  51  issues a connection request to a fixed IP address assigned in advance to the host device  10  to communicate with the host device  10  as a communication partner (step S 11 ), the network router  60  transmits the packet to the wireless packet communication network  40  according to the normal routing rule. Thus, the relay device of the wireless packet communication network  45  refers to the destination IP address of the packet, and makes connection to the communication module  25  of the telephone number corresponding to the IP address (step S 12 ). The communication module  25  notifies the connection adapter  1  of the reception of a call (step S 13 ). The connection adapter  1  relays the reception notification to the host device  10  (step S 14 ). Next, if the connection adapter  1  receives a response to the reception notification from the host device  10  (step S 15 ), it starts a connection establishing process by the PPP with the relay device. Specifically, the connection adapter  1  establishes a connection at the IP level to the relay device of the wireless packet communication network  45  by the LCP and the IPCP (step S 16  and S 17 ). The line control unit  121  of the connection adapter  1  passes bidirectionally the packet relating to the LCP and the IPCP. As described above, the host device  10  and the in-house LAN  50  can communicate with each other at the IP level. Therefore, data communication can be performed between them using an upper protocol such as the TCP/UDP etc. thereafter. Then, the network router  60  relays the connection request in step S 11  to the host device  10  (step S 18 ). Then, the network router  60  relays the response from the host device  10  (step S 19 ) to the managing computer  51  (step S 20 ). Thus, the communications can be made at the IP level between the host device  10  and the in-house LAN  50 , thereby starting the data communication using an upper protocol such as the TCP/UDP etc. thereafter (step S 21 ). The relay device of the wireless packet communication network  45  relays only the IP packets whose destination or source IP addresses are included in 192.168.0.0/28 (step S 22 ). 
     Next, the case in which the communication module  20  and the wireless packet communication network  40  in accordance with the CDMA standard are used without reforming or changing the host device  10  or the managing computer  51  is described below with reference to the attached drawings. 
     The communication procedure with the present system is described below with reference to the attached drawings. First, with reference to  FIGS. 10 and 11 , the case in which communications are started from the host device  10  to the managing computer  51  is described.  FIG. 20  is a sequence chart when communications are started from the host device to the managing computer.  FIG. 11  is an explanatory view of the converting process of the IP address described at the header of the IP packet transmitted from the host device. 
     As shown in  FIG. 10 , when the host device  10  issues an ‘ATDT080CCDD’ command to the connection adapter  1  (step S 101 ), the line control unit  121  of the connection adapter  1  converts the command into ‘ATD9999’, and transfers it to the communication module  20  (step S 102 ). The trigger of the issue of the command is the time when the IP packet addressed to 192.168.9.10 as shown in  FIG. 11  is generated, etc. BY the AT command, the communication module  20  issues a call to the relay device  41  in the wireless packet communication network  40  (step S 103 ). Upon receipt of the response ‘CONNECT’ indicating that the connection has been completed at the line level through the communication module  20  (step S 104 ), the line control unit  121  of the connection adapter  1  starts the process of connecting the connection adapter  1  to the in-house LAN  50  through the PPP. 
     First, the line control unit  121  of the connection adapter  1  starts an LCP negotiation with the relay device  41  of the wireless packet communication network  40  (step S 105 ). Next, the line control unit  121  of the connection adapter  1  performs a PAP authenticating process with the relay device  41  of the wireless packet communication network  40  (step S 106 ). The PAP authenticating process is not supposed by the host device  10  generated for the wireless packet communication network  45 . However, it is required when the wireless packet communication network  40  is used. Therefore, in the present embodiment, the connection adapter  1  performs the authenticating process on behalf of the host device  10 . When the authenticating process is completed, the line control unit  121  of the connection adapter  1  starts an IPCP negotiation between the connection adapter  1  and the relay device  41  of the wireless packet communication network  40  (step S 107 ). Thus, the IPCP negotiation is completed, and a dynamic IP address 172.16.0.X is assigned from the wireless packet communication network  40  to the line control unit  121  of the connection adapter  1 . The assigned IP address is predetermined for the communication module  20  as a connection terminal as described above. The assigned dynamic IP address is stored in the storage means such as the EPROM  151 . 
     When the PPP negotiation is completed, a response ‘CONNECT’ indicating that the connection has been completed at the line level is transmitted to the host device  10  (step S 108 ). The host device  10  receives the response, and starts LCP negotiation and the IPCP negotiation (steps S 109  and S 110 ). The point to note is that the line control unit  121  of the connection adapter  1  issues a response to the host device  10 . Thus, it seems to the host device  10  that the connecting process is being performed with the wireless packet communication network  45  described above with reference to  FIG. 8 . 
     Since the connection between the host device  10  and the in-house LAN  50  is completed in the above-mentioned process, the host device  10  starts data communications to the managing computer  51  (step S 111 ). The communication control unit  122  of the connection adapter  1  performs an address conversion on the header of the IP packet (step S 112 ). Specifically, as shown in  FIG. 11 , the fixed terminal IP address (192.168.0.1) and the dynamic terminal IP address (172.16.0.X) are mutually converted. With the process above, the communication with the managing computer  51  can be established which starts from the host device  10 . 
     Next, the case in which communications are started from the managing computer  51  of the in-house LAN  50  to the host device  10  is described with reference to  FIGS. 12 and 13 .  FIGS. 12 and 13  are sequence charts of the communications to be started from the managing computer.  FIG. 14  is an explanatory view of the step of converting an address. 
     In this process, it is assumed that the IP address 172.16.0.1 is assigned in the address management server  43  to the communication module  20  connected to the host device  10 . 
     When the managing computer  51  issues a connection request addressed to the IP address 172.16.0.1 of the communication module  20  connected to the host device  10  to communicate with the host device  10  as a communication partner (step S 151 ), the network router  60  relays the packet to the wireless packet communication network  40  according to the normal routing rule (step S 152 ). Here, the TCP packet as an upper layer of the IP packet has a SYN flag turned on, and the ACK flag turned off of the TCP header. The wireless packet communication network  40  according to the present embodiment is assumed to be a standard in which the first TCP packet relayed to the wireless packet communication network  40  has been unconditionally discarded. Therefore, since the managing computer  51  cannot receive a response corresponding to the communication start TCP packet within a predetermined time, it retransmits the communication start TCP packet (step S 151 - a ). 
     The wireless packet communication network  40  refers to the destination IP address of the packet received through the network router  60  (step S 151 - a ), acquires the telephone number corresponding to the IP address from the address management server  43 , and then transmits a message that the connection request is received from the in-house LAN  50  to the telephone number through the messaging service (step S 153 ). The wireless packet communication network  40  discards upon timeout a packet relating to the connection request received through the network router  60 . 
     The line control unit  121  of the connection adapter  1  that has received a message starts a connecting process to the first in-house LAN  50  on the basis of the set data stored in the set data storage unit  151   a.  Specifically, it transmits an ‘ATD9999’ command to the communication module  20  (step S 154 ). At the AT command, the communication module  20  issues a call to the relay device  41  in the wireless packet communication network  40  (step S 155 ). Upon receipt of a response ‘CONNECT’ indicating that the connection has been completed at the line level through the communication module  20 , the line control unit  121  of the connection adapter  1  (step S 156 ), the process of connecting the connection adapter  1  to the in-house LAN  50  is started by the PPP. 
     First, the line control unit  121  of the connection adapter  1  starts the LCP negotiation with the relay device  41  of the wireless packet communication network  40  (step S 157 ). Next, the line control unit  121  of the connection adapter  1  performs the PAP authenticating process with the relay device  41  of the wireless packet communication network  40  (step S 158 ). Next, the line control unit  121  of the connection adapter  1  starts the IPCP negotiation between the connection adapter  1  and the relay device  41  of the wireless packet communication network  40  (step S 159 ). Thus, the IPCP negotiation is completed, and a dynamic IP address 172.16.0.X is assigned to the line control unit  121  of the connection adapter  1  from the wireless packet communication network  40 . The assigned IP address is predetermined to the communication module  20  as a connection terminal as described above. The assigned dynamic IP address is stored in the storage means such as the EPROM  151  etc. 
     When the PPP negotiation is completed, a connection request packet from the managing computer  51  reaches the connection adapter  1  (step S 160 ). As described above, the wireless packet communication network  40  has discarded the packet transmitted by the managing computer  51  in step S 151 . Therefore, the managing computer  51  cannot receive a response of the connection request packet, and retransmits a connection request packet upon timeout (step S 151 - a,b ). In addition, since some time is required for the processes in steps S 153  to S 159 , the retransmitted packet further reaches timeout (step S 151 - a,b ). Therefore, the connection request packet reaching the connection adapter  1  is the latest packet in the packets retransmitted several times. In the present embodiment, the retransmission interval from step S 151  to S 151 - a  is 3 seconds, the retransmission interval from step S 151 - a  to S 151 - b  is 6 seconds, and the retransmission interval from step S 151 - b  to S 160  is 12 seconds. The retransmission interval depends on the implementation of the TCP/IP stack in the managing computer  51 . 
     Upon receipt of the connection request packet from the managing computer  51 , the line control unit  121  of the connection adapter  1  stores the connection request packet in the storage means such as the RAM  152  (step S 161 ), and notifies the host device  10  of the reception (step S 162 ). Upon receipt of the reception notification, the host device  10  notifies the connection adapter  1  of the response to the reception notification (step S 163 ), and starts the LCP negotiation and the IPCP negotiation (steps S 164 , S 165 ). The point to note is that the line control unit  121  of the connection adapter issues a response  1  to the host device  10 . Thus, it seems to the host device  10  that the connecting process is being performed with the wireless packet communication network  45  described above with reference to  FIG. 9 . 
     When the PPP negotiation is completed, the line control unit  121  of the connection adapter  1  transfers the connection request packet temporarily stored in the RAM  152  in step S 161  to the host device  10  (step S 166 ). Upon receipt of the connection request packet, the host device  10  issues the response to the connection adapter  1  (step S 167 ). The connection adapter  1  relays the response packet to the router  60  (step S 168 ). The router  60  relays the response packet to the managing computer  51  according to the normal routing rule (step S 169 ). 
     With the process above, the host device  10  completes the connection to the managing computer  51 , and starts the data communication to the managing computer  51  (step S 170 ). The communication control unit  122  of the connection adapter  1  performs an address conversion on the header of an IP packet (step S 171 ). Specifically, as shown in  FIG. 14 , a fixed terminal IP address (192.168.0.1) and a dynamic terminal IP address (172.16.0.1) are mutually converted. 
     As described above in detail, in the system according to the present embodiment, the network connection service of assigning a dynamic IP address can be used without changing or reforming the host device  10  and the managing computer  51  that use the network connection service of assigning a fixed IP. To be more concrete, although the network connection service of assigning a dynamic IP address is used, communications can be started from the managing computer  51  to the host device  10 . In addition, the source IP address of a packet received by the managing computer  51  is the fixed IP address assigned to the host device  10  in advance. Therefore, the managing computer  51  can identify a communication partner even if communications are started from the host device  10  to the managing computer  51 . 
     In addition, since the connection adapter  1  according to the present embodiment converts, discards, and passes data transmitted between the host device  10  and the communication modules  20 ,  25 , and  26  so that the data can be correctly processed in each equipment, various differences among the protocol service communication modules  20 ,  25 , and  26  in the wireless packet communication networks  40 ,  45 , and  46  can be appropriately absorbed. 
     Furthermore, the connection adapter  1  according to the present embodiment temporarily stores a communication start TCP packet received from the wireless packet communication network  40 , and when the host device  10  enters a communication state, the connection adapter  1  transmits the temporarily stored communication start TCP packet to a host device. That is, the host device  10  receives the TCP packet without waiting for the retransmission of the communication start TCP packet by the managing computer  51 . Thus, the communication start time between the host device  10  and the managing computer  51  can be shortened. 
     An embodiment of the present invention has been described above in detail, but the present invention is not limited to this application. For example, although a telemetering system for managing a vending machine in the above-mentioned embodiment, the present invention can be realized in other telemetering systems and telematics systems. 
     Also in the above-mentioned embodiment, the PDC standard, the CDMA standard, and the PHS standard are exemplified as communication modules, but other standards can be used in embodying the present invention. Similarly, any other interface standards on the host device side than those listed above can be applied. 
     Furthermore, in each of the above-mentioned embodiments, an authenticating method, an address system, an address assigning method (assigning a fixed IP address or a dynamic IP address) have been exemplified as differences between the network connection service in the wireless packet communication networks  45  and  46  and the network connection service in the wireless packet communication network  40 . However, the present invention can be applied when a difference is one of them or a combination of them. Furthermore, other differences can be absorbed by the connection adapter as necessary. For example, in the above-mentioned embodiment, a PAP authentication is performed by the wireless packet communication network  40 . However, for example, when a connection is made to a communication network in which a CHAP (Challenge Handshake Authentication Protocol) authentication is performed, the CHAP can be implemented to the connection adapter. 
     Furthermore, in each of the above-mentioned embodiments, the connection adapter  1  includes three communication modules  20 ,  25 , and  26  to make the wireless packet communication networks  40 ,  45 , and  46  arbitrarily available, but one of the communication modules  20 ,  25 , and  26  can be included and connected.