JP4081068B2 - Teleconferencing system - Google Patents

Description

  The present invention relates to a communication conference system suitable for use in a conference using a plurality of terminals connected via a communication line.

  Conventionally, in a system for holding a conference (conference), a conference server is specially installed, and the conference is realized by access to the conference server by all the participants. This conference server has an audio mixing function (MCU: Multipoint control unit) for mixing audio signals of each participant.

In addition, a configuration for realizing a communication conference system without using a conference server has been proposed. In this system, the conference is realized by using the mixing function of the client itself. That is, it is unnecessary to install a conference server by causing one or a plurality of terminals to function as MCUs. A simple and small-sized conference is realized by such a system.
JP 7-177145 A JP-A-8-32950 JP 2003-69969 A

  However, in a conventional system that does not use a conference server, a conference is held by instructing a destination (conference participant) by the terminal itself and dialing. Therefore, it has been necessary to recognize that the person or the terminal itself is a terminal functioning as an MCU. For example, when a terminal functioning as an MCU is disconnected during a conference, it may be necessary for other terminals to change the connection destination and change the terminal functioning as an MCU. In such a case, connection change and the like must be carried out by the user himself / herself and has not been automated.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a communication conference system that can automate terminal connection switching and improve convenience for users. To do.

In order to solve the above-described problem, the present invention is a communication conference system constructed using a server and a plurality of terminals, wherein the server is configured to receive the holding request terminal from the holding request terminal among the plurality of terminals. And a meeting holding request receiving means for receiving a meeting holding request including information on other terminals participating in the meeting, and a notification of a connection destination terminal to the holding request terminal, and continuously using the daisy chain method among the plurality of terminals. The terminal at the terminal to be connected is notified of the terminal at the connection source, and the terminal that is neither the event requesting terminal nor the terminal at the terminal among the continuously connected terminals is connected to the connection source and the connection destination connected by the daisy chain method. Connecting terminal notifying means for notifying the two terminals, connection instructing means for instructing the event requesting terminal to connect to a connection destination terminal, and a connection error among the plurality of terminals Error notification receiving means for receiving an error notification from the detected connection source terminal, and connection to another terminal through one connection port of a maximum of two connection ports among the plurality of terminals based on the error notification Detects a terminal other than the terminal that has detected the error, and transmits an instruction to establish a session with the terminal as a connection destination to the connection destination terminal in the connection in which the error has occurred. An error connection instruction means, and the terminal comprises a session establishment request means for requesting a connection establishment terminal to establish a session based on the connection instruction or the session establishment request. Teleconferencing system.

According to the present invention, in the above-described communication conference system, each of the plurality of terminals establishes at least two communication means for transmitting and receiving a multimedia signal based on an instruction from the server between the other terminals. A function of mixing (or synthesizing) or transferring a multimedia signal is executed by a terminal that has established two communication means with the communication device.

According to the present invention, in the communication conference system described above, the server instructs each terminal to connect each terminal, and a signal for connecting the terminals transmits a text information. The communication means for transmitting and receiving the multimedia signal is a session based on a protocol (SIP) different from the first communication protocol and suitable for streaming transmission of the multimedia signal. Features.

In addition, the present invention is a communication conference method in a communication conference system constructed using a server and a plurality of terminals, wherein the server is connected to the holding request terminal and the meeting from the holding request terminal of the plurality of terminals. A meeting holding request including information of other terminals participating in the communication is received, the holding request terminal is notified of a connection destination terminal, and a terminal connected continuously by the daisy chain method among the plurality of terminals is connected Notify the original terminal, and notify each terminal that is neither the event requesting terminal nor the terminal terminal among the continuously connected terminals of the connection source and the connection destination connected by the daisy chain method, The hosting terminal is instructed to connect to a connection destination terminal, receives an error notification from a connection source terminal that detects a connection error among the plurality of terminals, and receives the error notification. Based on the plurality of the terminals detects the maximum of two one terminal other than the terminal which has detected the error connection with another terminal by the connection port is a terminal which is not connected among the connection port An instruction for establishing a session with the terminal as a connection destination is transmitted to the connection destination terminal in the connection in which the error has occurred, and the terminal connects to the connection destination based on the connection instruction or the session establishment request. The communication conference method is characterized by requesting establishment of a session to the terminal of

Further, the present invention is constructed using a server and a plurality of terminals that request a connection destination terminal to establish a session based on a connection instruction from the server or a session establishment request from a connection source terminal. The meeting holding request receiving means for receiving, from the holding request terminal among the plurality of terminals, a meeting holding request including information on the holding request terminal and other terminals participating in the meeting, in the server in the communication conference system, the holding The requesting terminal is notified of the terminal of the connection destination, the terminal of the terminal continuously connected by the daisy chain method among the plurality of terminals is notified of the terminal of the connection source, and the event requesting terminal of the terminals connected continuously Connection terminal notifying means for notifying each terminal that is not the terminal terminal of the connection source and the connection destination terminal connected by the daisy chain method; A connection instructing unit for instructing a requesting terminal to connect to a connection destination terminal; an error notification receiving unit for receiving an error notification from a connection source terminal that detects a connection error among the plurality of terminals; Based on the plurality of terminals, a terminal other than the terminal that has detected the error is a terminal that is not connected to another terminal through one connection port out of a maximum of two connection ports. This is a program for executing an error connection instruction means for transmitting an instruction to establish a session with the terminal as a connection destination to the connection destination terminal in the connection in which the error has occurred.

Further, the present invention is the server in a communication conference system constructed using a server and a plurality of terminals that request connection establishment to a connection destination terminal based on a connection instruction or a session establishment request. A meeting holding request receiving means for receiving a meeting holding request including information on the holding request terminal and other terminals participating in the meeting from the holding request terminal of the plurality of terminals, and a connection destination to the holding request terminal Of the plurality of terminals, the terminal of the terminal that is continuously connected by the daisy chain method is notified of the terminal of the connection source, and the terminal that is continuously connected is not the terminal that requests the event or the terminal of the terminal Each terminal has a connection terminal notification means for notifying two terminals of a connection source and a connection destination connected by the daisy chain method; A connection instruction means for instructing connection to a terminal; an error notification receiving means for receiving an error notification from a connection source terminal that has detected a connection error among the plurality of terminals; and Of the two terminals, a terminal that is not connected to another terminal through one connection port out of a maximum of two connection ports, detects a terminal other than the terminal that detected the error, and connects the terminal A server comprising: an error connection instruction means for transmitting an instruction to establish a destination session to a connection destination terminal in the connection in which the error has occurred.

  According to the present invention, the server instructs each terminal to connect to each terminal, and at the maximum, two communication means for transmitting and receiving multimedia signals based on the instructions from the server at each terminal. Is established between terminals, and the function of mixing or synthesizing multimedia signals is executed by a terminal that has established two communication means with other terminals, so that installation of an MCU common to each terminal is omitted. In such a case, it is possible to automate connection switching between terminals.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing the configuration of an embodiment of the present invention. The communication conference system shown in FIG. 1 includes a server 10 and a plurality of terminals 21, 22, 23, 24, and 25 connected to the server 10 via communication lines.

  The server 10 is a computer, and an AP server (application server) 11 is executed on a predetermined OS (Operating System). The AP server 11 is a server called a Web (Web) application server, and at the application level by HTTP (HyperText Transfer Protocol) which is a communication protocol suitable for mainly transmitting text information to and from the terminals 21 to 25. Communication is performed, a request is received from the terminals 21 to 25, processing corresponding to the request is performed, and predetermined instructions and information are sent to the terminals 21 to 25. The server 10 also includes a DB (database) for managing the status of each terminal.

  The terminals 21 to 25 are computer terminals such as portable personal computers. In each of the terminals 21 to 25, a function for connecting to a predetermined communication line (communication network), a video shooting function, and an audio recording / playback function can be used. On each of the terminals 21 to 25, softphones 31 to 35, which are programs for realizing a communication conference, are executed. In general, a softphone is a terminal such as a personal computer or PDA (Personal Digital (Data) Assistants), and a predetermined program (application software) is executed to enable voice calls, videophone calls, etc. via a network such as the Internet. This is a function for realizing the communication. In the present embodiment, each of the softphones 31 to 35 can establish (generate) a session with up to two other softphones by SIP / RTP. Also, each of the softphones 31 to 35 communicates the connection destination of each session and instructions for changing the session from the AP server 11 and information on the number of video screens to be displayed on the display devices of the terminals 21 to 25 by communication using HTTP. Configured to obtain. Further, each of the softphones 31 to 35 can provide a function as an MCU, and the MCU mixes voice information sent from other terminals with voice information being recorded by its own terminal. It can be sent to other terminals. Further, the video signal may be multiplexed in a time division manner so that signals for a plurality of terminals may be transferred in one session, or video information or the like that is being captured by the own terminal may be further transmitted to the MCU. The information may be transferred by providing a function of combining and transmitting to other terminals.

  SIP (Session Initiation Protocol) is a protocol used in Internet conferences and Internet telephones that apply VoIP (Voice over Internet Protocol), and RTP (Real-time Transport Protocol) is a multimedia signal such as voice and video. This is a communication protocol suitable for streaming transmission.

  In the example shown in FIG. 1, five terminals 21 to 25 are connected in a daisy chain manner by establishing a maximum of two RTP sessions 51 to 54 as shown in FIG. However, the video and audio terminals are established by different sessions. Each soft phone 31 to 35 can use a maximum of two RTP ports 311, 312 to 351 and 352 per terminal. In this case, the terminal 21 (soft phone 31) and the terminal 25 (soft phone 35) located at the end of each of the terminals 21 to 25 (soft phones #A to #E) are each provided with one RTP port 311 and RTP. The port 352 is used to establish one session 51 and one session 54 with the terminal 22 (softphone 32) and the terminal 24 (softphone 34). On the other hand, the terminal 22 (softphone 32), the terminal 23 (softphone 33), and the terminal 24 (softphone 34) located in the middle part are respectively two RTP ports 321 and 322, 331 and 332, and 341 and 342 is used to establish each two sessions 51 and 52, 52 and 53, and 53 and 54 with other softphones.

  Accordingly, the MCU functions 42, 43, and 44 are executed in the terminal 22 (softphone 32), the terminal 23 (softphone 33), and the terminal 24 (softphone 34) located in the intermediate portion. In these terminals 22, 23, and 24, the MCU functions 42, 43, and 44 perform mixing (or synthesis) processing and transfer processing of multimedia signals such as voice.

  Further, each of the softphones 31 to 35 has a function of screening a connection terminal. In the present embodiment, each soft phone 31 to 35 receives an instruction by HTTP from the AP server 11, and a session between the designated soft phones is generated by SIP. At that time, each softphone determines whether or not the softphone that has requested connection is instructed from the AP server 11, and a session is established only when it is determined that the softphone has been instructed. (Screening function)

  Each session 51-54 is established by the data communication by SIP between each softphone 31-35. At this time, connection destination information such as a VoIP address (number) and an IP (Internet Protocol) address is notified from the AP server 11 to each of the softphones 31 to 35 by data communication using HTTP.

  In the configuration shown in FIG. 1, the software used when communicating between the AP server 11 and each of the softphones 31 to 35 is a component that can be commonly used by the OS running on the terminals 31 to 35 and the AP server 11. It is desirable to use (components). For example, when the OS is Windows (registered trademark), the AP server 11 can collect call states (connection states) of the respective softphones 31 to 35 using ActiveX (registered trademark), or each softphone 31 from the AP server 11. It is conceivable that instructions to .about.35 can be performed with ActiveX (same as above). In addition, the software configuration of the communication interface in each of the softphones 31 to 35 is desirably a form in which components that can be used are combined regardless of the language and the execution location.

  Next, an operation example of the configuration of FIG. 1 will be described with reference to FIG. FIG. 3 shows an example of the flow of processing when a communication conference is started with five terminals 21 to 25 in the configuration shown in FIG. In FIG. 3, the same components as those shown in FIG. However, in FIG. 3, the functions provided by the server 10 (or the AP server 11) are shown in a more detailed form. That is, the server 10 is divided into an input control unit 101, a connection control unit 102, a screen control unit 103, and a DB 104. The input control unit 101 is configured as an interface for inputting signals from the softphones 31 to 35. In order to instruct the connection destination to each of the softphones 31 to 35 or to process a signal indicating an error received from each of the terminals 21 to 25 when a connection error (failure) occurs. Realize the function. The screen control unit 103 realizes a function for instructing the content of an error message to be displayed on the screen by each of the softphones 31 to 35. In FIG. 3, it is assumed that data communication by HTTP is performed between these units 101 to 104.

  In FIG. 3, broken arrows indicate communication by HTTP, and solid arrows indicate communication by SIP. In addition, the conference start procedure is as follows. When there is a conference start request for a conference participant from a softphone, a line reservation is made for the requested participant's softphone, and each softphone is based on the reservation. It is assumed that the RTP session is directly established between the phones.

  In the example shown in FIG. 3, the user of the terminal 21 operates the softphone 31, so that the conference with the terminal 21 (user #A) and the terminals 22 to 25 (users #B to #E) as participants is performed. An opening request has been issued (S101). Receiving this, the input control unit 101 sends a connection request to the connection control unit 102 (S102). The connection control unit 102 accesses the DB 104 and collects information such as the user names and VoIP numbers of the softphones 31 to 35 as connection destinations in response to the connection request (S103).

  Next, the connection control unit 102 transmits a signal for requesting the softphones 31 to 35 to make a line reservation together with information on the connection destination VoIP number and the number of display screens by HTTP (S104 to S108). For example, to softphone 31 (user #A), a signal for requesting a line reservation with softphone 32 (user #B) as a connection destination is transmitted together with information indicating the number of screens “5” (= number of participants). At the same time, a connection instruction is requested (S104). For the soft phone 32 (user #B), a signal requesting a line reservation with the soft phone 31 (user #A) and the soft phone 33 (user #C) as connection destinations is displayed on the screen number “5” (= participation). It is transmitted together with information indicating the number of people (S105).

  Next, when the softphone 31 (user #A) requests the softphone 32 (user #B) to establish a session by SIP, and the softphone 32 performs screening and determines that connection is possible Establishes a session (S109). Next, when the softphone 32 (user #B) requests the softphone 33 (user #C) to establish a session by SIP, and the softphone 33 performs screening and determines that connection is possible The session is established (S110). Next, when the softphone 33 (user #C) requests the softphone 34 (user #D) to establish a session by SIP and the softphone 34 performs screening and determines that connection is possible. Establishes a session (S111).

  Next, in the example of FIG. 3, when the softphone 34 (user #D) requests the softphone 35 (user #E) to establish a session by SIP, it is assumed that some failure occurs (S112). ) The softphone 34 (user #D) transmits an error notification containing an error number indicating the type of error or the like to the input control unit 101 by HTTP (S113). The input control unit 101 transfers the error notification to the connection control unit 102 (S114), and the connection control unit 102 transfers the error notification to the screen control unit 103 again (S115).

  Based on the content of the received error notification, the screen control unit 103 outputs a signal instructing to display an error message on the softphones 34 and 35 in which an error has occurred and to indicate that reconnection is being performed in this example. Then, HTTP is transmitted to the softphone 34 and the softphone 35 (S116 to S117). The error message is generated by character or graphic information registered in advance according to the state of each softphone before the error and the content of the error.

  Next, the connection control unit 102 indicates a signal requesting the soft phone 35 (user #E) to make a line reservation with the soft phone 31 (user #A) as a connection destination, indicating the number of screens “5”. It is transmitted together (S118). That is, for the soft phone 35 (user #E) that has failed to be connected yet, the connection source (user #E) when the number of sessions has not yet reached “2” and an error has occurred. A signal for instructing establishment of a session with a softphone (user #A) that is not D) is transmitted by HTTP.

  Next, the connection control unit 102 sends a signal requesting the soft phone 31 (user #A) to make a line reservation with the soft phone 35 (user #E) as a connection destination, together with information indicating the number of screens “5”. Transmit (S119). Next, when the softphone 35 (user #E) requests the softphone 31 (user #A) to establish a session by SIP, and the softphone 31 performs screening and is determined to be connectable. The session is established (S120).

  Thus, in this embodiment, since the connection destination is instructed to each of the softphones 31 to 35 by the AP server 11, it is not necessary to manage the connection destination by each of the softphones 31 to 35 or the user. If the SIP session establishment fails, the error number is transmitted to the AP server 11, and the AP server 11 converts the error number into a character string or graphic information that is easy for the user to understand. A display request is sent to the corresponding softphone. At that time, since the content of the message can be determined according to the states of the plurality of softphones grasped by the AP server 11, for example, each softphone can display the message based on the SIP communication history or the like alone. However, it is possible to easily display an accurate and detailed message.

  In addition, although FIG. 3 demonstrated as an example the case where a connection failed, when a softphone using the MCU function stops the connection during the connection, both of the softphones are in the same manner as described above. If an error message is transmitted to the AP server 11, the connection can be switched to an appropriate connection destination.

  As described above, according to the present embodiment, the terminal state is managed by the AP server 11, so that the terminal side (softphone side) starts / continues the conference only by a passive operation according to an instruction from the AP server 11. Is possible. Further, by performing screening, it is possible to automatically reject incoming calls from other than the reserved conference participants. In addition, the AP server 11 and the softphones 31 to 35 cooperate to automatically perform reconnection when the softphone executing the MCU function leaves or reconnection when the connection fails.

  In FIG. 1, the conference participation terminal is only a soft phone, but even in the case of a hard phone, the transfer operation by this system is adopted by making it possible to use the function of the AP server 11 by changing the firmware or the like. It is possible to participate in a conference without a conference server.

  In the above embodiment, each user (softphone) has two lines (sessions) of call lines so that each user is connected in a daisy chain. VoIP conferences are provided for users who realize functions equivalent to MCU using two lines. In such a configuration, there are always two users with a vacant line (single user). Therefore, when a new user is added, instead of changing the connection of a plurality of users in the middle part, a session is established using a user with an empty line.

  Next, a modification of the configuration shown in FIG. 1 will be described with reference to FIG. In the system shown in FIG. 4, a server 60 is newly added to the configuration of FIG. 1 so that the function of the SIP-Proxy (proxy) server 61 can be used. In this configuration, it is possible to perform SIP communication not only directly between terminals but also via the SIP-Proxy 61. In FIG. 4, the same reference numerals are used for the same components as those in FIG. However, FIG. 4 shows only two terminals, the terminal 21 and the terminal 22. A broken line (large interval) indicates a signal flow by HTTP, and a broken line (small interval) indicates a signal flow by SIP.

  In the configuration shown in FIG. 4, for example, when a failure occurs when the session 51 is established from the softphone 31 to the softphone 32, the softphone 31 communicates with the AP server 11 by HTTP and an error signal and error message signal. The error message can be displayed by the softphone 31. Further, when an error occurs, the softphone 31 transmits an error number to the SIP-Proxy 61 by SIP. The SIP-Proxy 61 transmits this error number to the softphone 32 by SIP. Here, the softphone 32 can recognize the occurrence of an error, and the softphone 32 transmits and receives an error signal and an error message signal to and from the AP server 11 by HTTP, whereby the softphone 32 can display an error message. .

  According to the embodiment shown in FIG. 4, the softphone 31 that first recognizes the occurrence of an error notifies both the AP server 11 and the SIP-Proxy 61 of the occurrence of the error using different communication protocols. -The occurrence of an error can be recognized by SIP via Proxy 61.

  As described above, according to the present invention, a conference led by an AP server can be held regardless of a desk phone (hard phone) and an IP phone (soft phone) in a PC (personal computer). In addition, in the IP phone in the PC, since the call state can be monitored by cooperation of general-purpose communication components such as ActiveX (registered trademark), the no-call time can be reduced when the MCU is disconnected. This makes it possible to continue calling by automatically connecting to existing conferences. Similarly, when the call connection fails, the information can be reconnected automatically by the system.

  Note that the embodiment of the present invention is not limited to the above-described one, and modifications such as integration or distribution of functions realized by a terminal or a server can be made as appropriate. For example, the input control units 101 to DB 104 illustrated in FIG. 3 can be distributed and integrated. The embodiment of the present invention can be configured using a computer and software, and the software (program) in that case can be distributed via a computer-readable recording medium or a communication line. is there.

The system figure which shows the structure of one embodiment of this invention. Explanatory drawing which shows the connection form of each softphone 31-35 of FIG. The sequence diagram which shows the flow of the communication processing in the structure of FIG. The system diagram which shows the modification of embodiment of FIG.

Explanation of symbols

10, 60 server 11 AP server 21-25 terminal 31-35 soft phone 42-44 MCU
51-54 sessions (communication line)
61 SIP-Proxy server

Claims (6)

A communication conference system constructed using a server and a plurality of terminals,
The server
Meeting holding request receiving means for receiving a meeting holding request including information on the holding request terminal and other terminals participating in the meeting from the holding request terminal among the plurality of terminals,
The event request terminal is notified of a connection destination terminal, the terminal terminal continuously connected by the daisy chain method among the plurality of terminals is notified of the connection source terminal, and the event request among the continuously connected terminals Connection terminal notifying means for notifying each terminal that is neither a terminal nor the terminal terminal of the connection source and the connection destination connected by the daisy chain method;
A connection instruction means for instructing the connection to the terminal of the connection destination to the holding request terminal;
An error notification receiving means for receiving an error notification from a connection source terminal that has detected a connection error among the plurality of terminals;
Based on the error notification, a terminal other than the terminal that has detected the error and that is not connected to another terminal through one connection port out of a maximum of two connection ports among the plurality of terminals. And an error connection instruction means for transmitting an instruction to establish a session with the terminal as a connection destination to the connection destination terminal in the connection in which the error has occurred,
The communication conference system, wherein the terminal includes session establishment request means for requesting a connection destination terminal to establish a session based on the connection instruction or the session establishment request. Each of the plurality of terminals has established a maximum of two communication means for transmitting and receiving multimedia signals based on instructions from the server, and has established two communication means with other terminals. The communication conference system according to claim 1, wherein the terminal executes a function of mixing (or synthesizing) or transferring multimedia signals. The server instructs each terminal to connect between terminals, and a signal for connecting the terminals is made by a first communication protocol (HTTP) suitable for transmitting text information,
The communication means for transmitting and receiving the multimedia signal is a session based on a protocol (SIP) different from the first communication protocol and suitable for streaming transmission of the multimedia signal. The communication conference system according to claim 1 or 2. A communication conference method in a communication conference system constructed using a server and a plurality of terminals,
The server
From the holding request terminal among the plurality of terminals, a meeting holding request including information on the holding request terminal and other terminals participating in the conference is received,
The event request terminal is notified of a connection destination terminal, the terminal terminal continuously connected by the daisy chain method among the plurality of terminals is notified of the connection source terminal, and the event request among the continuously connected terminals Each terminal that is neither a terminal nor the terminal terminal is notified of two terminals of a connection source and a connection destination connected by the daisy chain method,
Instruct the connection request terminal to connect to the terminal to be held,
An error notification is received from a connection source terminal that has detected a connection error among the plurality of terminals,
Based on the error notification, a terminal other than the terminal that has detected the error and that is not connected to another terminal through one connection port out of a maximum of two connection ports among the plurality of terminals. And detecting an instruction to establish a session with the terminal as the connection destination to the connection destination terminal in the connection in which the error has occurred,
The terminal requests a connection establishment terminal to establish a session based on the connection instruction or the session establishment request. The communication conference system constructed using a server and a plurality of terminals that request session establishment from a connection destination terminal based on a connection instruction from the server or a session establishment request from a connection source terminal On the server,
A meeting holding request receiving means for receiving a meeting holding request including information on the holding request terminal and other terminals participating in the meeting from the holding request terminal among the plurality of terminals,
The event request terminal is notified of a connection destination terminal, the terminal terminal continuously connected by the daisy chain method among the plurality of terminals is notified of the connection source terminal, and the event request among the continuously connected terminals Connection terminal notifying means for notifying two terminals of a connection source and a connection destination connected by the daisy chain method to each terminal that is neither a terminal nor the terminal of the terminal,
Connection instruction means for instructing the connection to the terminal that is the connection destination to the holding request terminal,
An error notification receiving means for receiving an error notification from a connection source terminal that has detected a connection error among the plurality of terminals;
Based on the error notification, a terminal other than the terminal that has detected the error and that is not connected to another terminal through one connection port out of a maximum of two connection ports among the plurality of terminals. An error connection instruction means for transmitting an instruction to establish a session with the terminal as a connection destination to the connection destination terminal in the connection in which the error has occurred,
A program for running Server,
Based on a connection instruction or a session establishment request, a plurality of terminals that request the establishment of a session to a connection destination terminal, and
The server in the teleconference system constructed using
Meeting holding request receiving means for receiving a meeting holding request including information on the holding request terminal and other terminals participating in the meeting from the holding request terminal among the plurality of terminals,
The event request terminal is notified of a connection destination terminal, the terminal terminal continuously connected by the daisy chain method among the plurality of terminals is notified of the connection source terminal, and the event request among the continuously connected terminals Connection terminal notifying means for notifying each terminal that is neither a terminal nor the terminal terminal of the connection source and the connection destination connected by the daisy chain method;
A connection instruction means for instructing the connection to the terminal of the connection destination to the holding request terminal;
An error notification receiving means for receiving an error notification from a connection source terminal that has detected a connection error among the plurality of terminals;
Based on the error notification, a terminal other than the terminal that has detected the error and that is not connected to another terminal through one connection port out of a maximum of two connection ports among the plurality of terminals. And an error connection instruction means for transmitting an instruction to establish a session with the terminal as a connection destination to the connection destination terminal in the connection in which the error has occurred,
A server comprising:

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