Patent Publication Number: US-9432420-B2

Title: Communication system, non-transitory computer-readable medium storing communication program and communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This Application claims priority from JP2012-284965, filed on Dec. 27, 2012, the content of which is hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure relates to a communication system that is used to hold a remote conference, a non-transitory computer-readable medium storing a communication program for communication that is performed by a communication device to hold a remote conference, and a communication device. 
     A communication device that connects to a local area network (LAN) that is provided with a proxy server performs communication with a remote conference server that is connected to a network outside the LAN, via the proxy server, based on information set in relation to the proxy server (hereinafter referred to as “proxy setting”). Thus, the communication device is able to hold a remote conference with another communication device that connects to another LAN, via the remote conference server. 
     However, there are cases in which the proxy setting of a communication device for a certain LAN is not appropriate when the communication device connects to another LAN. For example, let us consider a LAN environment in which the proxy setting of the communication device is not set by automatic detection and it is necessary to directly specify an address and a port of the proxy server as the proxy setting. In this type of LAN environment, when the communication device connected to the certain LAN is moved and connected to another LAN, the moved communication device cannot detect a proxy server of the other LAN. Therefore, the moved communication device cannot perform communication with a remote conference server via the proxy server. In order to solve this problem, a technology is disclosed in which a server simultaneously changes settings of a plurality of computers. 
     SUMMARY 
     However, when the above-described technology is applied, if the proxy setting is not changed in one of the communication devices, setting change processing is not performed by the server. Therefore, when the communication device connected to a certain LAN is moved and connected to another LAN, the proxy setting of a communication device that is continuously connected to the other LAN is not changed. Therefore, the setting change processing is not performed by the server and the proxy setting of the moved communication device is not changed. Thus, the moved communication device cannot perform communication with the remote conference server via the proxy server. 
     The present disclosure provides a communication system including communication devices connected to a LAN, a non-transitory computer-readable medium storing a communication program that is used by a communication device connected to a LAN to appropriately perform communication via a proxy server provided in the LAN, and a communication device. 
     An aspect of the present disclosure provides a communication system includes a first communication device configured to connect to a local area network (LAN), and a second communication device configured to connect to the LAN. The first communication device includes a first processor and a first memory. The first memory stores computer-readable instructions. The instructions, when executed by the first processor, perform processes. The processes include a first communicating operation, a first determining operation, a second determining operation, a first transmitting operation, and a second communication operation. The first communicating operation communicates from inside the LAN with a conference server via a proxy server to establish a session for a remote conference between the first communication device and the conference server using a first proxy setting, the conference server is provided outside the LAN, the proxy server is provided inside the LAN, the first proxy setting is stored in a storage device of the first communication device and being a setting to communicate via a specific proxy server. The first determining operation determines whether the session has been established using the first proxy setting by the first communicating operation. The second determining operation determines, in response to the determination by the first determining operation that the session has not been established, whether LAN information identifying the LAN is included in history information stored in the storage device, the history information is information in which device information identifying another communication device with which a remote conference was held and a specific LAN information identifying a specific LAN to which the other communication device is connected are associated with each other. The first transmitting operation transmits, in response to the determination by the second determining operation that the LAN information identifying the LAN is included in the history information, setting request data to the second communication device identified by device information associated with the LAN information in the history information, the setting request data is data to request a second proxy setting and being data that includes at least first device information identifying the first communication device, the second proxy setting is a setting to communicate with the conference server from inside the LAN via the proxy server. The second communication operation communicates, in response to receiving of the second proxy setting from the second communication device, with the conference server to establish a session with the conference server using the received second proxy setting. The second communication device includes a second processor and a second memory. The second memory stores computer-readable instructions. The instructions, when executed by the second processor, perform processes. The processes include a third determining operation and a second transmitting operation. The third determining operation determines, in response to receiving of the setting request data from the first communication device, whether to transmit the second proxy setting stored in a storage device of the second communication device to the first communication device, based on the first device information included in the setting request data. The second transmitting operation transmits, in response to the determination by the third determining operation that the second proxy setting is to be transmitted to the other communication device, the second proxy setting to the first communication device. 
     Another aspect of the present disclosure provides a non-transitory computer-readable medium storing computer readable instructions, the instructions, when executed by a processor of a communication device, perform processes. The processes include a first communicating operation, a first determining operation, a second determining operation, a first transmitting operation, and a second communication operation. The first communicating operation communicates from inside a local area network (LAN) with a conference server via a proxy server to establish a session for a remote conference between the communication device and the conference server using a first proxy setting, the conference server being provided outside the LAN, the proxy server being provided inside the LAN, the first proxy setting being stored in a storage device of the communication device and being a setting to communicate via a specific proxy server. The second determining operation determines, in response to the determination by the first determining operation that the session has not been established, whether LAN information identifying the LAN is included in history information stored in the storage device, the history information being information in which device information identifying another communication device with which a remote conference was held and a specific LAN information identifying a specific LAN to which the other communication device is connected are associated with each other. The first transmitting operation transmits, in response to the determination by the second determining operation that the LAN information identifying the LAN is included in the history information, setting request data to a specific communication device identified by device information associated with the LAN information in the history information, the setting request data being data to request a second proxy setting and being data that includes at least device information identifying the communication device, the second proxy setting being a setting to communicate with the conference server from inside the LAN via the proxy server. The second communication operation communicates, in response to receiving of the second proxy setting from the specific communication device, with the conference server to establish a session for a remote conference between the communication device and the conference server using the received second proxy setting. 
     Yet another aspect of the present disclosure provides a communication device that includes a processor and a memory. The memory stores computer-readable instructions. The instructions, when executed by the processor, perform processes. The processes include a first communicating operation, a first determining operation, a second determining operation, a first transmitting operation, and a second communication operation. The first communicating operation communicates from inside a local area network (LAN) with a conference server via a proxy server to establish a session for a remote conference between the communication device and the conference server using a first proxy setting, the conference server being provided outside the LAN, the proxy server being provided inside the LAN, the first proxy setting being stored in a storage device of the communication device and being a setting to communicate via a specific proxy server. The second determining operation determines, in response to the determination by the first determining operation that the session has not been established, whether LAN information identifying the LAN is included in history information stored in the storage device, the history information being information in which device information identifying another communication device with which a remote conference was held and a specific LAN information identifying a specific LAN to which the other communication device is connected are associated with each other The first transmitting operation transmits, in response to the determination by the second determining operation that the LAN information identifying the LAN is included in the history information, setting request data to a specific communication device identified by device information associated with the LAN information in the history information, the setting request data being data to request a second proxy setting and being data that includes at least device information identifying the communication device, the second proxy setting being a setting to communicate with the conference server from inside the LAN via the proxy server. The second communication operation communicates, in response to receiving of the second proxy setting from the specific communication device, with the conference server to establish a session for a remote conference between the communication device and the conference server using the received second proxy setting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will be described below in detail with reference to the accompanying drawings in which: 
         FIG. 1  is a diagram illustrating an overview of a communication system  1  and an electrical configuration of a communication device  13 ; 
         FIG. 2  is a diagram illustrating a device information table  241 ; 
         FIG. 3  is a diagram illustrating a history information table  242 ; 
         FIG. 4  is a flowchart illustrating main processing; 
         FIG. 5  is a flowchart illustrating request processing; 
         FIG. 6  is a flowchart illustrating response processing; and 
         FIG. 7  is a flowchart illustrating response processing according to a modified example. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will be explained with reference to the drawings. A communication system  1  will be explained with reference to  FIG. 1 . The communication system  1  is provided with a conference server  6 , proxy servers  11  and  12  (hereinafter also collectively referred to as “proxy server(s)  10 ”) and communication devices  14  and  15  (hereinafter also collectively referred to as “communication device(s)  13 ”). A known multi-point control unit (MCU) is a specific example of the conference server  6 . A known personal computer (PC) is a specific example of the communication device  13 . The conference server  6  is connected to an Internet  18 . The proxy server  12  is provided inside a first local area network (LAN)  2 . The communication device  15  that is connected to the first LAN  2  can perform communication with the conference server  6  via the proxy server  12 . The proxy server  11  is provided inside a second LAN  3 . The communication device  14  that is connected to the second LAN  3  can perform communication with the conference server  6  via the proxy server  11 . The network address “255.255.255.0” is assigned to the first LAN  2 , and the network address “255.255.0.0” is assigned to the second LAN  3 . Hereinafter, the first LAN  2  and the second LAN  3  are also collectively referred to as a “LAN  4 ”. Further, each of the communication devices  14  and  15  is assigned identification information (hereinafter also referred to as a “device ID”) that is the same as the reference number of each of the communication devices  14  and  15 . Note that the number of the communication devices  13  that are connected to the LAN  4  is not limited to the example shown in  FIG. 1 . Further, a plurality of LANs that are different from the first LAN  2  and the second LAN  3  may be connected to the Internet  18 . Further, a dedicated communication line may be used instead of the Internet  18 . 
     The communication system  1  is a remote conference system that allow a remote conference to be held between users of the communication devices  13  by transmitting and receiving video and audio between two or more of the communication devices  13  via the conference server  6 . When the users of the communication devices  13  participate in the remote conference, each of the users inputs a conference ID and a code number to the communication device  13  via a keyboard  263 . The conference ID is unique identification information that is specified for each remote conference. The conference ID is necessary to newly start a remote conference or to participate in the remote conference that has already been started. For example, a number of given digits is used as the conference ID. The conference ID may be a URL that identifies a unique resource of the conference server  6 . That is, the CPU (not shown in the drawings) of the conference server  6  may generate a resource that is different for each of remote conferences so that each remote conference can be identified. The CPU  21  of the communication devices  13  may access to an URL that indicates the resource received from the conference server  6 . The code number is a password that is necessary to participate in a remote conference, and is assigned in advance to each remote conference that is identified by the conference ID. When the conference ID and the code number are input, a CPU  21  of the communication device  13  transmits the conference ID and the code number to the conference server  6 , and thus the remote conference is started. 
     Note that the conference ID and the code number are determined in advance by a CPU (not shown in the drawings) of the conference server  6 . The CPU of the conference server  6  associates the determined conference ID and code number, and stores the associated conference ID and code number in a registration table  61  that is stored in an HDD (not shown in the drawings). When each of the users of the plurality of communication devices  13  takes part in the remote conference, the CPU of the conference server  6  notifies each of the users of the determined conference ID and code number. For example, the notification of the conference ID and the code number is performed by the CPU of the conference server  6  distributing e-mail, in which the conference ID and the code number are described, to each of the communication devices  13 . Note that the communication devices  13  to which the conference ID and the code number are notified are set in advance for each conference ID by the communication device  13  of an organizer who sets up the remote conference. 
     When the conference ID and the code number are received from the communication device  13 , the CPU of the conference server  6  refers to the registration table  61  and thereby determines whether to allow the communication device  13  to participate in the remote conference that is identified by the conference ID. When the CPU of the conference server  6  allows the communication device  13  to participate in the remote conference, the CPU of the conference server  6  associates the conference ID with the device ID of the communication device  13  that is allowed to participate in the remote conference, and stores the associated conference ID and device ID in a conference table  62  that is stored in the HDD. Note that, the CPU of the conference server  6  may associate the conference ID with a user ID in addition to the device ID and store in the conference table  62 . In this case, the CPU  21  of the communication device  13  transmits the user ID in addition to the conference ID and the code number to the conference server  6 . By doing this, the user of the communication device  13  that is allowed to participate in the remote conference is able to participate in the remote conference identified by the conference ID and to have a conversation with the user of the other communication device  13 . Note that, in the following embodiment, various tables that is identified by the device ID are stored (refer to  FIG. 2  and  FIG. 3 ). In a case where, the user ID is transmitted from the communication device  13  to the conference server  6 , the various tables that is identified by the user ID may be stored. 
     Note that a series of communication that is performed between the conference server  6  and the communication device  13  in order to hold a remote conference is hereinafter referred to as a “session.” A situation in which a session becomes possible between the conference server  6  and the communication device  13  is referred to as “the session is established.” After the session with the conference server  6  is established, the communication device  13  holds the remote conference by performing mutual communication with the other communication device  13 . 
     Note that the communication device  13  may hold the remote conference by directly performing mutual communication with the other communication device  13  without going through the conference server  6 . The remote conference may be a call system in which a conversation is made between the users of the communication devices  13  by transmitting and receiving audio only between the communication devices  13 . 
     An electrical configuration of the communication device  13  will be explained. The communication device  13  is provided with the CPU  21  that performs overall control of the communication device  13 . The CPU  21  is electrically connected to a ROM  22 , a RAM  23 , a hard disk drive (HDD)  24 , a communication interface (I/F)  25 , an input I/F  26 , an output I/F  27  and a drive device  28 . A boot program, a basic input output system (BIOS) and the like are stored in the ROM  22 . A timer, a counter and temporary data are stored in the RAM  23 . Further, the conference ID of the remote conference that is currently being held is stored in the RAM  23 . Programs that cause the CPU  21  to execute main processing (to be described later, refer to  FIG. 4 ) and response processing (refer to  FIG. 6  and  FIG. 7 ) are stored in the HDD  24 . Further, a device information table  241  (to be described later, refer to  FIG. 2 ) and a history information table  242  (to be described later, refer to  FIG. 3 ) are stored in the HDD  24 . Further, setting information (hereinafter referred to as “proxy setting”) to perform communication with a proxy server  10  that is provided inside the LAN  4  to which the communication device  13  is connected is stored in the HDD  24 . The proxy setting includes an IP address and a port number of the proxy server  10 . 
     The communication I/F  25  is an interface to connect the communication device  13  to the LAN  4 . The input I/F  26  is an interface to connect a microphone  261 , a camera  262  and the keyboard  263  to the communication device  13 . The output I/F  27  is an interface to connect a speaker  271  and a display  272  to the communication device  13 . The drive device  28  reads information stored in a storage medium  281 . For example, when the communication device  13  is set up, a program stored in the storage medium  281  is read by the drive device  28  and is stored in the HDD  24 . Note that the CPU  21  of the communication device  13  may receive the program via the Internet  18  and may store the program in the HDD  24 . In this case, the program is stored in a storage medium, such as an HDD, that is provided in a server (not shown in the drawings) that is connected via the Internet  18 . 
     When the communication device  13  that connects to the LAN  4  in which the proxy server  10  is provided performs communication with the conference server  6  that connects to the Internet  18 , the communication device  13  performs communication using, as a destination, the IP address and the port number that are included in the proxy setting stored in the HDD  24 . Hereinafter, performing communication with the proxy server  10  using the IP address and the port number included in the proxy setting as the destination is differently expressed as “performing communication with the proxy server  10  using the proxy setting.” In place of the communication device  13 , the proxy server  10  performs communication with the conference server  6 . Thus, the communication device  13  is able to perform communication with the conference server  6  via the proxy server  10 . On the other hand, when the proxy setting is not stored in the HDD  24  of the communication device  13  or when the proxy setting is wrong, the communication device  13  cannot perform communication with the proxy server  10  and therefore cannot perform communication with the conference server  6 . 
     Therefore, normally, the proxy setting of the proxy server  10 , which is provided inside the LAN  4  to which the communication device  13  is connected, is input to the communication device  13  by the user via the keyboard  263  or the like. For example, the proxy setting of the proxy server  12  (the IP address “192.168.10.8” and the port number “8080”) is input to the communication device  15  that connects to the first LAN  2 , and the proxy setting of the proxy server  11  (the IP address “192.168.0.10” and the port number “8080”) is input to the communication device  14  that connects to the second LAN  3 . The CPU  21  of each of the communication devices  14  and  15  stores the input proxy setting in the HDD  24 . Thus, the communication devices  14  and  15  are able to perform communication with the proxy servers  11  and  12 , respectively, using the proxy setting stored in the HDD  24 . Therefore, the communication devices  14  and  15  are able to hold a remote conference with each other via the conference server  6 , by respectively performing communication with the conference server  6  via the proxy servers  11  and  12 . 
     Hereinafter, the proxy setting of the proxy server  11  is also referred to as a “first proxy setting” and the proxy setting of the proxy server  12  is also referred to as a “second proxy setting.” 
     Note that there is a known technology in which the communication device  13  uses a web proxy auto discovery (WPAD) protocol and automatically acquires the proxy setting of the proxy server  10  from a server other than the proxy server  10  provided in the LAN to which the communication device  13  is connected. It is thus possible to perform communication with the proxy server  10  without requiring an input operation of the proxy setting. However, in the present disclosure, a situation is assumed in which the communication device  13  cannot automatically acquire the proxy setting of the proxy server  10 . As this type of situation, a case is considered in which, for example, the communication device  13 , for which the IP address and the port number of the proxy server  10  are directly specified as the proxy setting, connects to the LAN having the other proxy server  10 . Further, a case is considered in which the communication device  13  that specifies auto detection (the use of the WPAD protocol) in the proxy setting is connected to the LAN that is not compatible with the WPAD protocol. 
     The device information table  241  (refer to  FIG. 2 ) and the history information table  242  (refer to  FIG. 3 ) that are stored in the HDD  24  of the communication device  13  will be explained. As an example, a case will be described in which remote conferences have been held a plurality of times in the past between the communication devices  14  and  15  by the communication device  15  performing communication with the conference sever  6  via the proxy server  12  and the communication device  14  performing communication with the conference server  6  via the proxy server  11 . The device information table  241  and the history information table  242  that are stored in the HDD  24  of the communication device  14  will be specifically explained. 
     Note that it is assumed that the proxy setting to perform communication with the conference server  6  via the proxy server  11  or  12  has been input to each of the communication devices  14  and  15  in advance by the user. Specifically, it is assumed that the second proxy setting of the proxy server  12 , which is provided inside the first LAN  2  to which the communication device  15  connects, is stored in the HDD  24  of the communication device  15 , and the first proxy setting of the proxy server  11 , which is provided inside the second LAN  3  to which the communication device  14  connects, is stored in the HDD  24  of the communication device  14 . 
     The device information table  241  will be explained with reference to  FIG. 2 . Note that a device information table  2411  indicates the device information table  241  before update, and a device information table  2412  indicates the updated device information table  241 . The device ID, the IP address and the network address (hereinafter referred to as the “NW address”) are associated with each other and stored in the device information table  241 . The device ID of the device information table  241  is identification information that identifies the communication device  13  itself that stores the device information table  241  in the HDD  24 . The IP address of the device information table  241  is a local IP address that is assigned to the communication device  13  in the LAN  4  to which the communication device  13  identified by the corresponding device ID connects. The NW address of the device information table  241  is a local network address that is assigned to the LAN  4  to which the communication device  13  identified by the corresponding device ID connects. As described above, the information relating to the communication device  13  itself is stored in the device information table  241 . 
     The device ID that is stored in the device information table  241  is input by the user via the keyboard  263  or the like. The IP address and the NW address that are stored in the device information table  241  are automatically notified to the communication device  13  by a dynamic host configuration protocol (DHCP) server (not shown in the drawings) that is provided in the LAN  4 . The CPU  21  of the communication device  13  acquires the IP address and the NW address notified by the DHCP server provided in the LAN  4 , and stores the IP address and the NW address in the device information table  241 . Note that the IP address and the NW address that are stored in the device information table  241  may be directly input by the user via the keyboard  263  or the like. 
     For example, in the case of the device information table  2411 , the device ID “14” of the communication device  14  is stored, the IP address “192.168.0.1” that is assigned to the communication device  14  in the second LAN  3  to which the communication device  14  connects is stored, and the NW address “255.255.0.0” assigned to the second LAN  3  to which the communication device  14  connects is stored. 
     Although not shown in the drawings, in the device information table  241  that is stored in the HDD  24  of the communication device  15 , the device ID “15” of the communication device  15  is stored, the IP address “192.168.10.1” that is assigned to the communication device  15  in the first LAN  2  to which the communication device  15  connects is stored, and the NW address “255.255.255.0” assigned to the first LAN  2  to which the communication device  15  connects is stored. 
     The history information table  242  will be explained with reference to  FIG. 3 . The device ID, the IP address, the NW address and the number of conferences are associated and stored in the history information table  242 . The device ID of the other communication device  13  that has participated in the remote conference held in the past and the device ID of the other communication device  13  that is participating in the remote conference currently being held are stored as the device ID. The IP address is an IP address assigned to the communication device  13  that is identified by the corresponding device ID. The NW address is a network address assigned to the LAN  4  to which the communication device  13  identified by the corresponding device ID connects. The number of conferences is the number of remote conferences that have been held with the communication device  13  identified by the corresponding device ID. As described above, the information relating to the other communication device  13  in the remote conference held in the past and the remote conference currently being held is stored in the history information table  242 . 
     In the case of  FIG. 3 , since the communication device  14  has held remote conferences with the communication device  15  in the past, the ID “15” of the communication device  15  is stored as the device ID. Note that, when the communication device  14  has held a remote conference with the communication device  13  other than the communication device  15 , the device ID of the communication device  13  other than the communication device  15  is stored separately from the device ID “15”. Further, when three or more of the communication devices  13  perform communication with each other and participate in the same remote conference, the device IDs of all the other communication devices  13  that participate in the remote conference are stored. The device ID “15” is stored in association with the IP address “192.168.10.1” assigned to the communication device  15  identified by the device ID “15”, and with the NW address “255.255.255.0” assigned to the first LAN  2  to which the communication device  15  connects. Further, since “10” is stored as the number of conferences, the communication device  14  has held the remote conference with the communication device  15  ten times in the past. 
     Although not shown in the drawings, in the history information table  242  that is stored in the HDD  24  of the communication device  15 , the device ID “14” of the communication device  14  is stored, the IP address “192.168.0.1” that is assigned to the communication device  14  in the second LAN  3  to which the communication device  14  connects is stored, and the NW address “255.255.0.0” assigned to the second LAN  3  to which the communication device  14  connects is stored. 
     It is assumed that the communication device  14  is moved and its state is changed from a state in which the communication device  14  is connected to the second LAN  3  to a state in which the communication device  14  is connected to the first LAN  2  (refer to an arrow  5  in  FIG. 1 ). The CPU  21  of the communication device  14  stores the IP address “192.168.10.2” and the NW address “255.255.255.0”, which are notified by the DHCP server (not shown in the drawings) provided inside the first LAN  2 , in the device information table  2411  stored in the HDD  24  of the communication device  14 , and thus updates the device information table  2411 . The notified IP address “192.168.10.2” is an IP address that is assigned to the communication device  14  in the newly connected first LAN  2 . The notified NW address “255.255.255.0” is a NW address assigned to the newly connected first LAN  2 . As a result, the device information table  2411  (refer to  FIG. 2 ) is updated to the device information table  2412  (refer to  FIG. 2 ). 
     It is assumed that the communication device  14  starts communication with the conference server  6  in order to start a remote conference with the communication device  15 . Since the first proxy setting is stored in the HDD  24  of the communication device  14 , the CPU  21  of the communication device  14  attempts to perform communication with the proxy server  11  using the first proxy setting. However, since the proxy server  12  is provided in the first LAN  2  and the second proxy setting of the proxy server  12  is not stored in the HDD  24  of the communication device  14 , the communication device  14  cannot perform communication with the proxy server  12 . Therefore, the communication device  14  cannot establish a session by performing communication with the conference server  6 , and cannot start the remote conference with the communication device  15 . 
     To address this, the CPU  21  of the communication device  14  cannot perform communication with the conference server  6  using the first proxy setting stored in the HDD  24 . When it is not possible to establish a session with the conference server  6 , the CPU  21  of the communication device  14  acquires the second proxy setting in the following manner. First, the CPU  21  of the communication device  14  refers to the device information table  2412  (refer to  FIG. 2 ) and the history information table  242  (refer to  FIG. 3 ) that are stored in the HDD  24 . Based on the device information table  2412  and the history information table  242 , the CPU  21  of the communication device  14  identifies the communication device  15  with which a remote conference has been held in the past and which is connected to the first LAN  2  to which the communication device  14  is newly connected. 
     Specifically, the communication device  15  is identified in the following manner. The NW address “255.255.255.0” that is stored in the device information table  2412  is also stored in the history information table  242 . Therefore, the CPU  21  of the communication device  14  identifies, from the history information table  242 , the communication device  15  that is identified by the device ID “15” corresponding to the NW address“255.255.255.0”. 
     Next, the CPU  21  of the communication device  14  requests the identified communication device  15  to set the second proxy setting of the proxy server  12  that is provided inside the first LAN  2  (an arrow  7 ). When predetermined conditions (details will be described later) are satisfied, the CPU  21  of the communication device  15  notifies the communication device  14  of the second proxy setting in response to the request (an arrow  8 ). The CPU  21  of the communication device  14  stores the second proxy setting notified by the communication device  15  in the HDD  24 . 
     In order to establish a session with the conference server  6 , the CPU  21  of the communication device  14  starts communication with the proxy server  12  using the second proxy setting stored in the HDD  24 . The second proxy setting has already been used by the communication device  15  to perform communication with the proxy server  12 . Therefore, the communication device  14  can perform communication with the proxy server  12  using the second proxy setting. Therefore, the communication device  14  is able to establish a session with the conference server  6  via the proxy server  12 . If the communication device  15  has also established a session with the conference server  6 , the communication device  14  is able to hold a remote conference with the communication device  15  via the conference server  6 . 
     As described above, the CPU  21  of the communication device  14  can acquire the second proxy setting from the communication device  15 . Therefore, the user of the communication device  14  need not input, to the communication device  14 , the second proxy setting that has been acquired, for example, by sending an enquiry to an administrator of the first LAN  2 . 
     The processing that is performed by the CPU  21  of the communication device  13  will be explained in detail with reference to flowcharts shown in  FIG. 4  to  FIG. 6 . When an instruction to activate a remote conference application to hold a remote conference with the other communication device  13  is input by the user via the keyboard  263 , the CPU  21  starts the main processing (refer to  FIG. 4  and  FIG. 5 ) by reading and executing the program stored in the HDD  24  of the communication device  13 . The response processing (refer to  FIG. 6 ) is activated and started during the main processing. The main processing and the response processing are performed in parallel with each other. Note that the main processing and the response processing are not limited to the example that is performed by the CPU  21 , and may be performed by another electronic component (for example, an application specific integrated circuit (ASIC)). Further, the main processing and the response processing may be distributed and performed by a plurality of electronic devices (that is, a plurality of CPUs). Further, part of the main processing and the response processing may be performed by the CPU of the conference server  6 . 
     Note that, in the main processing explained below, it is assumed that the first proxy setting is stored in advance in the HDD  24  of the communication device  14 , and the main processing that is performed by the CPU  21  of the communication device  14  will be explained. 
     The main processing will be explained with reference to  FIG. 4 . The main processing will be specifically explained using an example in which the communication device  14  is connected to the second LAN  3  (refer to  FIG. 1 ). First, the CPU  21  activates the response processing (refer to  FIG. 6 ) (step S 11 ). The response processing will be described in detail later. The CPU  21  activates the remote conference application. The CPU  21  displays, on the display  272 , an input screen on which the conference ID and the code number can be input and a start button and an end button can be selected. In a state in which the conference ID and the code number have been input via the input screen, the CPU  21  determines whether the start button that is used to instruct the start of a remote conference has been selected (step S 13 ). When the start button has not been selected (no at step S 13 ), the CPU  21  determines whether the end button that is used to instruct the end of the remote conference application has been selected (step S 35 ). When the end button has been selected (yes at step S 35 ), the CPU  21  ends the remote conference application that has been activated and thereafter ends the main processing. When the end button has not been selected (no at step S 35 ), the CPU  21  returns the processing to step S 13 . The CPU  21  repeats the processing at step S 13 . 
     It is assumed that the user of the communication device  14  inputs, to the communication device  13  via the keyboard  263 , the conference ID and the code number notified in advance by the conference server  6  and selects the start button. When the start button is selected in a state in which the conference ID and the code number have been input (yes at step S 13 ), the CPU  21  starts processing to hold the remote conference. In order to establish a session with the conference server  6 , the CPU  21  transmits establishment request data that requests the establishment of the session to the proxy server  11  that is provided inside the second LAN  3  (step S 15 ). The establishment request data includes the conference ID and the code number input via the input screen, and the device ID “14” of the communication device  14 . When the CPU  21  transmits the establishment request data to the proxy server  12 , the CPU  21  uses the first proxy setting stored in the HDD  24 . The CPU  21  starts monitoring of reception of establishment response data that is transmitted from the conference server  6  in response to the establishment request data. The establishment response data is transmitted from the conference server  6  when the conference server  6  permits the establishment of the session in response to the establishment request data. 
     Since the first proxy setting of the proxy server  11  is stored in the HDD  24  of the communication device  14 , it is possible to perform communication with the proxy server  11  using the first proxy setting. In this case, the proxy server  11  receives the establishment request data transmitted from the communication device  14  and transmits the establishment request data to the conference server  6 . The CPU of the conference server  6  receives the establishment request data, and acquires the conference ID, the code number and the device ID “14” that are included in the establishment request data. When a combination of the acquired conference ID, code number and device ID is stored in the registration table  61  (refer to  FIG. 1 ), the CPU of the conference server  6  permits the establishment of the session with the communication device  14  that has transmitted the establishment request data. In this case, the CPU of the conference server  6  associates the conference ID and the device ID acquired from the establishment request data and stores the associated conference ID and device ID in the conference table  62  (refer to  FIG. 1 ). In order to notify the communication device  14  that the session establishment is permitted, the CPU of the conference server  6  transmits the establishment response data to the proxy server  11  that has transmitted the establishment request data. The proxy server  11  receives the establishment response data from the conference server  6 . The proxy server  11  transmits the received establishment response data to the communication device  14  that has transmitted the establishment request data. 
     When the communication device  14  receives the establishment response data that has been transmitted from the conference server  6  in response to the establishment request data transmitted at step S 15 , the CPU  21  establishes the session with the conference server  6  (yes at step S 17 ). The communication device  14  becomes able to hold the remote conference identified by the conference ID with the other communication device  13  which has specified the conference ID that is the same as the conference ID included in the establishment request data and which has established the session with the conference server  6 . The CPU  21  stores the conference ID input via the input screen, in other words, the conference ID of the remote conference started by establishing the session, in the RAM  23  as the conference ID of the remote conference that is currently being held. 
     When a session is newly established with the communication device  14 , the CPU of the conference server  6  refers to the conference table  62  and thereby identifies all the communication devices  13  that participate in the remote conference held by the newly established session. The CPU of the conference server  6  transmits ID notification data to all the identified communication devices  13 . The ID notification data is transmitted to all the communication devices  13  that participate in the remote conference, in order to notify them of the device IDs of the other communication devices  13  that participate in the remote conference. The ID notification data is repeatedly transmitted in a predetermined cycle. 
     A specific explanation will be given using an example in which, in a state in which the remote conference that is identified by the conference ID “12345” is held by a session established between the communication device  14  and the conference server  6 , a session is newly established between the communication device  15  and the conference server  6  and the communication device  15  participates in the remote conference identified by the conference ID “12345”. The CPU of the conference server  6  selects, from the conference table  62 , the device IDs “14” and “15” that are associated with the conference ID “12345”. The CPU of the conference server  6  transmits the ID notification data that includes the selected device ID “14” to the communication device  15  that is identified by the selected device ID “15”. Further, the CPU of the conference server  6  transmits the ID notification data that includes the selected device ID “15” to the communication device  14  that is identified by the selected device ID “14”. 
     After the CPU  21  of each of the communication devices  14  and  15  has established the session with the conference server  6  (yes at step S 17 , refer to  FIG. 4 ), when the ID notification data is transmitted from the conference server  6 , the CPU  21  of each of the communication devices  14  and  15  receives the ID notification data. The received ID notification data includes the device ID of the other communication device  13  that participates in the remote conference (the conference ID “12345”) that is currently being held. When the ID notification data is received, the CPU  21  acquires the device ID included in the ID notification data. The CPU  21  determines whether the acquired device ID is stored in the RAM  23 , and thereby determines whether there is another of the communication devices  13  that has newly participated in the remote conference that is currently being held (step S 23 ). When the CPU  21  receives the ID notification data from the conference server  6  and the device ID acquired from the received ID notification data is not stored in the RAM  23 , the CPU  21  determines that the communication device  13  that is identified by the acquired device ID is the communication device  13  that has newly participated in the remote conference that is currently being held (yes at step S 23 ). In order to notify the communication device  13  identified by the acquired device ID of information relating to the communication device  14  itself, the CPU  21  transmits information notification data to the conference server  6  (step S 25 ). The information notification data includes the device ID, the IP address and the NW address stored in the device information table  241  (refer to  FIG. 2 ). Further, the information notification data includes a destination device ID of the information notification data, which is a device ID that is not stored in the RAM  23  among the device IDs acquired from the ID notification data. The CPU  21  stores the device ID acquired from the ID notification data in the RAM  23  (step S 27 ). The CPU  21  returns the processing to step S 23  and repeats the processing. 
     When the information notification data is received from the communication device  14 , the CPU of the conference server  6  acquires the destination device ID included in the information notification data. The CPU of the conference server  6  transmits the received information notification data to the communication device  13  that is identified by the acquired destination device ID. 
     When the ID notification data is not received from the conference server  6  or when the device ID acquired from the received ID notification data is stored in the RAM  23  (no at step S 23 ), the CPU  21  determines whether the information notification data has been received from the conference server  6  (step S 29 ). When the information notification data has not been received (no at step S 29 ), the CPU  21  advances the processing to step S 37 . 
     On the other hand, when the information notification data has been received from the conference server  6  (yes at step S 29 ), the CPU  21  acquires the device ID, the IP address and the NW address included in the received information notification data. The communication device  13  that is identified by the acquired device ID is the communication device  13  that has newly participated in the remote conference that is currently being held. The CPU  21  stores the acquired device ID, IP address and NW address in the history information table  242  (refer to  FIG. 3 ) (step S 31 ). The CPU  21  associates “1” with the number of conferences and stores the associated information in the history information table  242  (step S 33 ). The CPU  21  advances the processing to step S 37 . 
     Note that, when the device ID that is the same as the device ID acquired from the information notification data has already been stored in the history information table  242 , the CPU  21  replaces the IP address and the NW address stored in association with the same device ID with the IP address and the NW address acquired from the information notification data (step S 31 ). Further, the CPU  21  updates the number of conferences by adding “1” to the corresponding number of conferences (step S 33 ). The CPU  21  advances the processing to step S 37 . In this manner, the CPU  21  can easily create and manage the history information table  242 . 
     At step S 37 , the CPU  21  determines whether an instruction to end the remote conference that is currently being held has been input via the keyboard  263  (step S 37 ). When the instruction to end the remote conference has not been input (no at step S 37 ), the CPU  21  returns the processing to step S 23 . On the other hand, when the instruction to end the remote conference has been input (yes at step S 37 ), the CPU  21  transmits, to the conference server  6 , withdrawal notification data to notify withdrawal from the remote conference that is currently being held. The withdrawal notification data includes the device ID “14” of the communication device  14  itself and the conference ID of the remote conference that is currently being held. The CPU  21  terminates the session with the conference server  6 . The CPU  21  returns the processing to step S 13 . 
     When the withdrawal notification data is received from the communication device  13 , the CPU of the conference server  6  acquires the device ID and the conference ID that are included in the withdrawal notification data. The CPU of the conference server  6  deletes the acquired device ID, among the device IDs that have been associated with the acquired conference ID and stored in the conference table  62  (refer to  FIG. 1 ). The conference server  6  terminates the session with the communication device  13  that has transmitted the withdrawal notification data. 
     A specific explanation will be given using an example in which the communication device  14  is moved from the second LAN  3  (refer to  FIG. 1 ) and is connected to the first LAN  2  (refer to  FIG. 1 ). Note that the device information table  241  stored in the HDD  24  of the communication device  14  is updated from the device information table  2411  (refer to  FIG. 2 ) to the device information table  2412  (refer to  FIG. 2 ) by the communication device  14  being connected to the first LAN  2 . 
     Since the proxy server  12  is provided in the first LAN  2 , the communication device  14  cannot perform communication with the proxy server  12  even if the communication device  14  uses the first proxy setting to perform communication with the proxy server  11 . Therefore, the CPU  21  cannot receive the establishment response data in response to the establishment request data transmitted at step S 15 , and it cannot establish a session with the conference server  6  (no at step S 17 ). In this case, the CPU  21  determines that the session is not established using the first proxy setting when the establishment request data is not received. In this case, in order for the communication device  14  to transmit the establishment request data to the conference server  6  and to establish the session with the conference server  6 , it is necessary to acquire the second proxy setting of the proxy server  12  and to store the second proxy setting in the HDD  24 . The CPU  21  performs request processing (refer to  FIG. 5 ) in order to acquire the second proxy setting from the communication device  13  that connects to the first LAN  2  to which the communication device  14  connects (step S 19 ). 
     The request processing will be explained with reference to  FIG. 5 . The CPU  21  refers to the device information table  2412  (refer to  FIG. 2 ) and acquires the NW address “255.255.255.0” (step S 41 ). The CPU  21  determines whether the NW addresses that are not the target of the processing at step S 45  to step S 51  remain in the history information table  242  (refer to  FIG. 3 ) (step S 43 ). When the NW addresses that are not the target of the processing at step S 45  to step S 51  remain in the history information table  242  (yes at step S 43 ), the CPU  21  selects one of the NW addresses that are not the target of the processing at step S 45  to step S 51  (step S 45 ). The CPU  21  determines whether the NW address “255.255.255.0” acquired from the device information table  241  at step S 41  matches the NW address selected from the history information table  242  at step S 45  (step S 47 ). When it is determined that the two NW addresses are different from each other (no at step S 47 ), the CPU  21  returns the processing to step S 43 . 
     As shown in  FIG. 1 , the NW address “255.255.255.0” acquired from the device information table  241  at step S 41  is stored in the history information table  242  (refer to  FIG. 3 ). The CPU  21  determines that the NW address “255.255.255.0” acquired from the device information table  241  at step S 41  matches the NW address selected from the history information table  242  at step S 45  (yes at step S 47 ). That is, the NW address of the first LAN  2  to which the communication device  14  attempts to connect is included in the history information table  242 . In this case, it is indicated that the communication device  14  has held a remote conference in the past with the communication device  15  that is identified by the device ID “15” associated with the NW address “255.255.255.0” that is determined at step S 47  to match the NW address selected from the history information table  242 . Note that the communication device  15  connects to the first LAN  2  to which the communication device  14  connects. 
     The CPU  21  acquires, from the history information table  242 , the device ID “15” associated with the NW address “255.255.255.0” that is determined to match at step S 47 . The CPU  21  transmits setting request data, which requests transmission of the proxy setting, to the communication device  15  identified by the acquired device ID “15” (step S 51 ). The setting request data includes the device ID stored in the device information table  241 , in other words, the device ID “14” of the communication device  14  itself. Further, the setting request data includes the conference ID and the code number input via the input screen. The setting request data is transmitted to the IP address “192.168.10.1” that is associated with the NW address “255.255.255.0” in the history information table  242 . 
     The CPU  21  of the communication device  15  that has received the setting request data transmitted from the communication device  14  sends back setting response data or rejection response data to the communication device  13  (step S 81 , step S 83 , refer to  FIG. 6 ). After transmitting the setting request data to the communication device  15  at step S 51 , the CPU  21  of the communication device  14  starts to monitor reception of the setting response data or the rejection response data to be sent back from the communication device  15 . 
     When the CPU  21  receives the setting response data from the communication device  15  after transmitting the setting request data to the communication device  15  at step S 51  (yes at step S 53 ), the CPU  21  acquires the second proxy setting included in the setting response data. The CPU  21  replaces the first proxy setting stored in the HDD  24  with the acquired second proxy setting, and thereby updates the proxy setting stored in the HDD  24  (step S 55 ). The CPU  21  ends the request processing and returns the processing to the main processing (refer to  FIG. 4 ). 
     On the other hand, when the CPU  21  receives the rejection response data from the communication device  15  after transmitting the setting request data to the communication device  15  at step S 51  (no at step S 53 , yes at step S 57 ), the CPU  21  cannot acquire the second proxy setting. In this case, the CPU  21  returns the processing to step S 43  in order to repeatedly perform the processing at step S 43  to step S 51  based on the other NW addresses stored in the history information table  242 . 
     Meanwhile, when the CPU  21  does not receive the setting response data and the rejection response data from the communication device  15  after transmitting the setting request data to the communication device  15  at step S 51  (no at step S 57 ), the CPU  21  determines whether a predetermined time period (for example, 10 seconds) has elapsed after transmitting the setting request data at step S 51  (step S 59 ). When the predetermined time period has not elapsed (no at step S 59 ), the CPU  21  returns the processing to step S 53  in order to continue to monitor the reception of the setting response data or the rejection response data to be sent back from the communication device  15 . When the predetermined time period has elapsed (yes at step S 59 ), the CPU  21  returns the processing to step S 43  in order to repeatedly perform the processing at step S 43  to step S 51  based on the other NW addresses stored in the history information table  242 . 
     As shown in  FIG. 4 , after the request processing (step S 19 ) ends, the CPU  21  determines whether the first proxy setting stored in the HDD  24  has been updated to the second proxy setting (step S 21 ). When the rejection response data has been received in the request processing (refer to  FIG. 5 ) (yes at step S 57 , refer to  FIG. 5 ), or when no response has been received from the conference server  6  in the request processing (no at step S 59 ), the first proxy setting stored in the HDD  24  has not been updated (no at step S 21 ). In this case, it is indicated that the communication device  14  is not able to participate in the remote conference of the conference ID input via the input screen displayed on the display  272 , and therefore, the CPU  21  returns the processing to step S 13 . The CPU  21  continues to display the input screen on the display  272  and continues to monitor whether another conference ID and another code number are input. 
     On the other hand, when the setting response data has been received in the request processing (refer to  FIG. 5 ) (yes at step S 53 , refer to  FIG. 5 ), the first proxy setting stored in the HDD  24  has been updated to the second proxy setting (step S 55 , refer to  FIG. 5 ). When it is determined that the first proxy setting has been updated to the second proxy setting (yes at step S 21 ), the CPU  21  returns the processing to step S 15 . 
     At step S 15 , the CPU  21  transmits the establishment request data to the proxy server  12  in order to establish a session with the conference server  6  (step S 15 ). When the CPU  21  transmits the establishment request data to the proxy server  12 , the CPU  21  uses the second proxy setting. The second proxy setting has been acquired from the communication device  15  that connects to the first LAN  2  to which the communication device  14  connects. The communication device  15  is performing communication with the proxy server  12  using the second proxy setting. For that reason, the communication with the proxy server  12  that is performed using the second proxy setting succeeds. The CPU  21  receives the establishment response data that is transmitted from the conference server  6  in response to the establishment request data, and establishes the session with the conference server  6  (yes at step S 17 ). The CPU  21  stores the conference ID input via the input screen, in other words, the conference ID of the remote conference started by the establishment of the session, in the RAM  23 . 
     The response processing will be explained with reference to  FIG. 6 . Note that the response processing will be explained below on the assumption that the second proxy setting of the proxy server  12  that is provided inside the first LAN  2  to which the communication device  15  connects is stored in advance in the HDD  24 . A case will be explained in which the response processing is performed by the CPU  21  of the communication device  15  that is connected to the first LAN  2  (refer to  FIG. 1 ). 
     The CPU  21  determines whether the setting request data has been received (step S 71 ). When the setting request data has not been received (no at step S 71 ), the CPU  21  advances the processing to step S 85 . At step S 85 , the CPU  21  determines whether the end button to instruct the end of the remote conference application has been selected (step S 85 ). When the end button has been selected (yes at step S 85 ), the CPU  21  ends the remote conference application that has been activated and thereafter ends the response processing. When the end button has not been selected (no at step S 85 ), the CPU  21  returns the processing to step S 71 . The CPU  21  repeats the processing at step S 71 . 
     It is assumed that the communication device  14  that has been moved from the second LAN  3  is connected to the first LAN  2  (the arrow  5 , refer to  FIG. 1 ) and the setting request data is transmitted from the communication device  14  (step S 51 , refer to  FIG. 5 ). The CPU  21  receives the setting request data (yes at step S 71 ). 
     The CPU  21  acquires the device ID “14” and the conference ID “12345” included in the received setting request data. The CPU  21  searches the history information table  242  (refer to  FIG. 3 ) (step S 73 ). The CPU  21  determines whether the acquired device ID “14” is stored in the history information table  242  (step S 75 ). When the acquired device ID “14” is not stored in the history information table  242  (no at step S 75 ), it means that a remote conference has not been held in the past with the communication device  14  identified by the device ID “14”. In this case, in order to inhibit the communication device  14  that has transmitted the setting request data from establishing a session with the conference server  6 , the CPU  21  transmits the rejection response data to the communication device  14  (step S 83 ). The CPU  21  advances the processing to step S 85 . 
     When the communication device  14  connected to the first LAN  2  receives the rejection response data in response to the setting request data (yes at step S 57 , refer to  FIG. 5 ), the communication device  14  cannot acquire the second proxy setting to perform communication with the proxy server  12 , and thus cannot perform communication with the proxy server  12 . Therefore, the communication device  14  cannot establish a session with the conference server  6 . 
     When the device ID acquired from the setting request data is stored in the history information table  242  (yes at step S 75 ), the CPU  21  determines whether the conference ID acquired from the setting request data is stored in the RAM  23  (step S 76 ). Note that, when the communication device  15  has established a session with the conference server  6 , the conference ID input via the input screen, in other words, the conference ID of the remote conference that is currently being held, is stored in the RAM  23 . When the conference ID acquired from the setting request data is not stored in the RAM  23  (no at step S 76 ), the remote conference in which the communication device  14  that has transmitted the setting request data attempts to participate is different from the remote conference that is currently being performed by the communication device  15  itself. In this case, in order to inhibit the communication device  14  that has transmitted the setting request data from establishing a session with the conference server  6 , the CPU  21  transmits the rejection response data to the communication device  14  (step S 83 ). The CPU  21  advances the processing to step S 85 . 
     On the other hand, when the conference ID acquired from the setting request data is stored in the RAM  23  (yes at step S 76 ), the remote conference in which the communication device  14  that has transmitted the setting request data attempts to participate matches the remote conference that is currently being performed by the communication device  15  itself. The CPU  21  refers to the history information table  242 , and acquires the number of conferences that is associated with the device ID acquired from the setting request data. The CPU  21  determines whether the acquired number of conferences is equal to or more than a predetermined number (ten) (step S 77 ). When the acquired number of conferences is less than the predetermined number (no at step S 77 ), the CPU  21  transmits the rejection response data to the communication device  14  in order to inhibit the communication device  14  that has transmitted the setting request data from establishing a session with the conference server  6  (step S 83 ). The CPU  21  advances the processing to step S 85 . 
     When the acquired number of conferences is equal to or more than the predetermined number (yes at step S 77 ), the CPU  21  transmits the setting response data to the communication device  14  that has transmitted the setting request data (step S 81 ). The setting response data includes the second proxy setting stored in the HDD  24 . The CPU  21  returns the processing to step S 71 . 
     Note that the CPU  21  of the communication device  14  that has received the setting response data in response to the setting request data acquires the second proxy setting included in the received setting response data, and stores the second proxy setting in the HDD  24  (step S 55 , refer to  FIG. 5 ). The CPU  21  of the communication device  14  is able to perform communication with the proxy server  12  provided inside the first LAN  2 , by using the second proxy setting stored in the HDD  24 . It is thus possible to establish the session with the conference server  6  and to start the remote conference. 
     As explained above, the communication device  13  transmits the setting request data to the other communication device  13  that connects to the LAN  4  to which the communication device  13  connects (step S 51 ). Thus, the communication device  13  is able to acquire, from the other communication device  13 , the second proxy setting of the proxy server  10  provided inside the LAN  4  (yes at step S 53 ). The communication device  13  updates the first proxy setting stored in the HDD  24  to the acquired second proxy setting (step S 55 ). Thus, the communication device  13  is able to perform communication with the conference server  6  via the proxy server  10  provided inside the LAN  4 . Therefore, even when the second proxy setting is not stored in advance in the HDD  24 , the communication device  13  is able to appropriately perform communication with the conference server  6  via the proxy server  10  and to establish a session with the conference server  6  (yes at step S 17 ). 
     For example, as shown in  FIG. 1 , when the communication device  14  in which the first proxy setting of the proxy server  11  is stored in the HDD  24  is moved from the second LAN  3  and is connected to the first LAN  2 , the second proxy setting of the proxy server  12  provided inside the first LAN  2  is not stored in the HDD  24 . Therefore, the communication device  14  cannot perform communication with the conference server  6  via the proxy server  12 . To address this, the communication device  14  transmits the setting request data to the communication device  15  with which a remote conference has been held in the past via the conference server  6 . Thus, the communication device  14  acquires the second proxy setting from the communication device  15  and stores it in the HDD  24 . The communication device  14  is able to perform communication with the proxy server  12  by using the second proxy setting stored in the HDD  24 , and it is thus possible to perform communication with the conference server  6  via the proxy server  12  and to establish a session with the conference server  6 . Therefore, even when the communication device  14  does not have the function to automatically acquire the proxy setting from the proxy server  12  and to set the proxy setting, the communication device  14  is able to hold a remote conference by establishing a session with the conference server  6 . 
     Further, when the communication device  13  receives the setting request data from the other communication device  13 , the communication device  13  transmits the setting response data to the other communication device  13  and thereby notifies the other communication device  13  of the second proxy setting (step S 79 ). This makes it possible for the other communication device  13  to perform communication with the conference server  6  via the proxy server  10 . 
     Further, when the communication device  13  receives the setting request data from the other communication device  13  with which a remote conference has been held in the past (yes at step S 75 ), the communication device  13  transmits the setting response data and thereby notifies the other communication device  13  of the second proxy setting (step S 79 ). The communication device  13  does not notify the other communication device  13  with which no remote conference has been held in the past of the second proxy setting (no at step S 75 ). In this manner, the communication with the conference server  6  that is performed via the proxy server  10  can be limited to the other communication device  13  with which a remote conference has been held in the past. It is thus possible to improve security of the LAN  4 . 
     When the number of conferences with the other communication device  13  is equal to or more than the predetermined number (yes at step S 77 ), the communication device  13  transmits the second proxy setting (step S 79 ). When the number of conferences with the other communication device  13  is less than the predetermined number (no at step S 77 ), the communication device  13  does not transmit the second proxy setting. In this manner, the communication device  13  can limit the communication with the conference server  6  that is performed via the proxy server  10  to the other communication device  13  with which remote conferences have been held at least the predetermined number of times. It is thus possible to further improve the security of the LAN  4 . 
     When the remote conference that is the same as the remote conference that is scheduled to be held after the other communication device  13  establishes a session with the conference server  6  is already being held (yes at step S 76 ), the communication device  13  notifies the other communication device  13  of the second proxy setting (step S 79 ). When the session with the conference server  6  has not been established or when the same remote conference is not being held (no at step S 76 ), the communication device  13  does not notify the other communication device  13  of the second proxy setting. In this manner, the communication device  13  can limit the communication that is performed via the proxy server  10  to the other communication device  13  that attempts to participate in the remote conference that is currently being held. It is thus possible to further improve the security of the LAN  4 . 
     Note that the present disclosure is not limited to the above-described embodiment and various modifications are possible. Hereinafter, modified examples of the present disclosure will be explained. 
     Response processing according to a modified example of the present disclosure will be explained with reference to  FIG. 7 . Note that the modified response processing shown in  FIG. 7  is activated at step S 11  of the main processing shown in  FIG. 4  and is started. Processing that is the same as in the response processing (refer to  FIG. 6 ) according to the above-described embodiment is denoted by the same reference numeral, and an explanation thereof is omitted here. 
     The response processing according to the modified example differs from the response processing (refer to  FIG. 6 ) according to the above-described embodiment in the following points. When the setting request data is received (yes at step S 71 ), the CPU  21  acquires the conference ID, the code number and the device ID included in the setting request data. When the conference ID acquired from the setting request data is stored in the RAM  23  (yes at step S 76 ), in other words, when the remote conference in which the communication device  14  that has transmitted the setting request data attempts to participate is currently being performed by the communication device  15  itself, the CPU  21  transmits authentication request data to the conference server  6  in order to request authentication of the communication device  14  from the conference server  6  (step S 91 ). The authentication request data includes the device ID acquired from the setting request data, in other words, the device ID “14” of the communication device  14  that has transmitted the setting request data. Further, the authentication request data includes the conference ID and the code number acquired from the setting request data. The conference server  6  receives the authentication request data transmitted from the communication device  13 . 
     The CPU of the conference server  6  acquires the device ID “14”, the conference ID and the code number included in the received authentication request data. The CPU of the conference server  6  determines whether the acquired device ID “14”, conference ID and code number have been associated with each other and stored in the registration table  61  (refer to  FIG. 1 ). When the acquired device ID “14”, conference ID and code number have been associated with each other and stored in the registration table  61 , or when transmission of the setting response data to the communication device  14  identified by the device ID “14” is permitted and the acquired device ID “14”, conference ID and code number have not been stored in the registration table  61 , the CPU of the conference server  6  prohibits the transmission of the setting response data to the communication device  14 . The CPU of the conference server  6  transmits authentication response data, which includes permission/non-permission of the transmission of the setting response data, to the communication device  14  that has transmitted the authentication request data. 
     The CPU  21  of the communication device  15  receives the authentication response data transmitted from the conference server  6  (step S 93 ). The CPU  21  acquires information included in the received authentication response data. When the information that permits the transmission of the setting response data is acquired (yes at step S 95 ), the CPU  21  transmits the setting response data to the communication device  14  that has transmitted the setting request data (step S 81 ). On the other hand, when the information that prohibits the transmission of the setting response data is acquired (no at step S 95 ), the CPU  21  transmits the rejection response data to the communication device  14  that has transmitted the setting request data (step S 83 ). 
     As explained above, in the modified example, the communication device  15  determines whether to transmit to the communication device  14  the setting response data that notifies the communication device  14  of the second proxy setting, by transmitting an enquiry to the conference server  6  (step S 91 ). When the transmission of the setting request data is permitted by the conference server  6  (yes at step S 95 ), the communication device  15  transmits the setting response data to the communication device  14  and thereby notifies the communication device  14  of the second proxy setting (step S 81 ). On the other hand, when the transmission of the setting request data is prohibited by the conference server  6  (no at step S 95 ), the communication device  15  transmits the rejection response data to the communication device  14  (step S 83 ) and does not notify the communication device  14  of the second proxy setting. In this manner, the communication device  15  can limit the communication that is performed via the proxy server  12  to the communication device  14  that is permitted by the conference server  6 . It is thus possible to further improve the security of the first LAN  2 . 
     In the above-described embodiment, the CPU  21  uses the NW address as the information that identifies the LAN  4 . When the NW address stored in the device information table  241  is stored in the history information table  242 , the CPU  21  determines that the communication device  13  identified by the device ID associated with this NW address is the other communication device  13  that connects to the same LAN  4  (step S 47 ). However, the information that identifies the LAN  4  is not limited to the NW address. The CPU  21  may identify the LAN  4  using information that is different from the NW address. For example, the CPU  21  may identify the LAN  4  by a domain name that is assigned to the LAN  4 . 
     In the above-described embodiment, the CPU  21  identifies the communication device  13  using the device ID. However, the information that identifies the device ID is not limited to the device ID. The CPU  21  may identify the communication device  13  using information that is different from the device ID. For example, the CPU  21  may identify the communication device  13  using an IP address that is assigned to the communication device  13 . 
     In the above-described embodiment, the device information table  241  and the history information table  242  are stored in the HDD  24  of the communication device  13 . However, the device information table  241  and the history information table  242  may be stored in a medium other than the HDD  24  of the communication device  13 . For example, the device information table  241  and the history information table  242  may be stored in an HDD of the conference server  6 . 
     In the above-described modified example, the CPU  21  transmits the authentication request data to the conference server  6  (step S 91 ), and based on the authentication response data that is sent back from the conference server  6 , the CPU  21  determines whether to perform notification of the second proxy setting (step S 93 , step S 95 ). The transmission destination of the authentication request data is not limited to the conference server  6 . For example, the CPU  21  may transmit the authentication request data to an authentication server (not shown in the drawings) that is connected to the Internet  18 . The CPU  21  may determine whether to perform notification of the second proxy setting, based on the authentication response data that is sent back from the authentication server. 
     In the above-described embodiment, when the setting request data is received (yes at step S 71 ), when the device ID acquired from the setting request data is stored in the history information table  242  (yes at step S 75 ), when the conference ID acquired from the setting request data is stored in the RAM  23  (yes at step S 76 ), and when the number of conferences is equal to or more than ten (yes at step S 77 ), the CPU  21  transmits the setting response data (step S 83 ). However, the CPU  21  may determine whether to transmit the setting response data using a method other than that described above. For example, the CPU  21  may determine whether to transmit the setting response data, based on a table that stores in advance the device ID of the communication device  13  to which the setting response data is to be transmitted. Note that the table may be input in advance by the user via the keyboard  263 . In this case, the CPU  21  may use a table that is used for another purpose. Further, for example, the CPU  21  may accumulate the number of the communication devices  13  that have transmitted the setting response data and may store the accumulated number in the RAM  23 . The CPU  21  may transmit the setting response data to the communication device  13  that has transmitted the setting request data when the accumulated number of the communication devices  13  is less than a predetermined number, and the CPU  21  may prohibit the transmission of the setting response data to the communication device  13  that has transmitted the setting request data when the accumulated number of the communication devices  13  is equal to or more than the predetermined number. 
     The CPU  21  may store cumulative time, which is the accumulated time of the participation in the remote conferences, instead of storing the number of conferences in the history information table  242 . When the setting request data is received, the CPU  21  may refer to the cumulative time that is associated with the device ID of the communication device  13  that has transmitted the setting request data. The CPU  21  may transmit the setting response data when the cumulative time is a predetermined time or more, and the CPU  21  may prohibit the transmission of the setting response data when the cumulative time is less than the predetermined time.