JP2006060473A - Data communication method, client and data communication program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform real time communication in a server-less environment without complicating a processing in a client and without increasing the traffic of a network. <P>SOLUTION: A first client 14 receives data inputted to itself and transmits the data to multicast addresses and respective second clients 16 receive the data from the multicast addresses. In the first client, in the case of receiving a speech request from the second client 16-1, the connection of peer to peer communication with the second client 16-1 relating to the speech request is established. The first client 14 receives the data transmitted by the peer to peer communication from the second client 16-1, composes the data inputted to itself and the received data and transmits the composite data to the multicast addresses. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to content distribution and real-time communication, and more particularly to a data communication method and a data communication program suitable for an electronic conference system.

  With the spread of the Internet, electronic conferencing is being introduced by placing terminals in each of the separated offices and communicating voice and content in real time between the terminals.

In a conventional electronic conference system, a server is arranged at any location, and a peer-to-peer (P2P) communication path is provided between each client used by a conference participant and the server. Through which the audio data, image data, and the like are transmitted, and the audio data, image data, and the like are received from the server. The server repeats the process of receiving data from each client and sending the data to each client to be transmitted. Therefore, there is a problem that the load on the server becomes very large.
JP 2004-178236 A

  On the other hand, for example, Patent Document 1 discloses a technique for realizing real-time communication between clients in a serverless environment. However, in this technique, since all other clients send and receive data with each other by multicast, traffic on the network increases. Therefore, in order to realize such a system, it is necessary to construct a network capable of a large amount of data communication, and there is a problem that the system construction cost increases.

  Further, in all clients connected to the network, it is necessary to mix and reproduce data received from the multicast address, for example, audio data, which complicates the client processing. For this reason, it is necessary to improve the performance of the client, and as a result, the system construction cost increases.

  The present invention provides a data communication method, a client, and a data communication program for realizing real-time communication in a serverless environment without complicating processing in the client and increasing network traffic. Objective.

  An object of the present invention is a data communication method between a first client and one or more second clients, each connected via a network, wherein the first client is connected to the first client. Accepting the input data and transmitting the data to a multicast address; receiving the data from the multicast address at each of the second clients; and second at the first client. Establishing a connection for peer-to-peer communication with the caller's second client when the request to speak is received from the client at the first client; , Transmitted by peer-to-peer communication from the caller's second client Receiving the received data, combining the data input to the first client with the data received from the second client of the caller, and combining the combined data in the first client. And transmitting to a multicast address. This is achieved by a data communication method comprising the steps of:

  According to the present invention, the data from the caller's second client and the data accepted by the first client are combined and multicast transmitted, for example, a second other than the caller's second client. Received by clients. In the electronic conference, the organizer data accepted by the first client and the data from the caller are combined, and the combined data is multicast-received by the second client. Since data is transmitted by multicast transmission from the first client to the second client except for the caller, an increase in traffic can be suppressed. Further, since the first client is basically multicast transmission, it is possible to suppress an increase in processing load.

  In a preferred embodiment, when a peer-to-peer communication connection is established between the caller's second client and the first client, the caller's second client is established at the first client. Transmitting the data input to the first client to the second client by peer-to-peer communication; and in the second client of the caller, instead of receiving from the multicast address Receiving data transmitted from the first client by peer-to-peer communication.

  According to this embodiment, the second client of the caller basically receives data transmitted to the multicast address and peers with the first client only when starting the data. -Data is transmitted and received by two-peer communication. Accordingly, the processing load on the second client can be suppressed.

  In a more preferred embodiment, when there are a plurality of second clients of the caller, the data input to the first client by the second client of the certain caller in the first client. Combining the data of the second client of the caller other than the second client of the certain caller, and the second client of the certain caller in the first client, Transmitting the synthesized data by peer-to-peer communication.

  In another preferred embodiment, when the second client is connected to another network that is not multicast capable, a virtual network connection with tunneling from the network causes the second client to Receiving the data.

  In addition, an object of the present invention is a first client connected to a second client via a network, and accepts input data and transmits the data to a multicast address. A peer-to-peer processing means for establishing a peer-to-peer communication connection with a second client of a caller in response to a speech request from the second client; Peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the caller's second client; data received from the caller's second client; Combining processing means for combining the received data, and the multicast transmission means multicasts the data from the combining processing means. Also achieved by a first client and transmits to the addressed address.

  In a preferred embodiment, the peer-to-peer processing means is inputted to a first client of a certain caller when the plurality of second clients of the caller is plural. The data and the data of the second client of the caller other than the second client of the certain caller, and the peer-to-peer transmission / reception means sends the combined data to the caller's second client. Send to the second client.

  In another preferred embodiment, a second client connected to the first client via a network receives a multicast receiving means for receiving data transmitted from the first client to a multicast address; A peer-to-peer processing means for establishing a peer-to-peer communication connection with one client and a peer for performing data transmission / reception with the first client by peer-to-peer communication And, when performing peer-to-peer communication with the first client, instead of receiving data from the multicast receiving means, the peer-to-peer transmission / reception Means receive data transmitted by peer-to-peer communication from the first client.

  Furthermore, an object of the present invention is a data communication program that can be read by a first client connected to a second client via a network, the first client accepting input data, Multicast transmission means for transmitting the data to the multicast address, and connection of peer-to-peer communication with the second client of the caller according to the request for speech in response to the request for speech from the second client Peer-to-peer processing means for establishing data, peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the caller's second client, and The data received from the second client and the input data are made to function as a synthesis processing means, Multicast transmission means, the data from the combining processing unit, so as to sent to the multicast address, is also achieved by a data communication program characterized by operating the first client.

In a preferred embodiment, when the first client functions as a peer-to-peer processing means, when there are a plurality of second clients of the caller, a second client of a caller , Operating the first client to synthesize data input to the first client and data of a second client of a caller other than the second client of the certain caller, and When the first client functions as the peer-to-peer transmission / reception means, the first client is configured to transmit the combined data to the second client of the certain caller. The object of the present invention is also readable by a second client connected to the first client via a network. Multicast receiving means for receiving data transmitted from the first client to a multicast address, and peer-to-peer communication with the first client A peer-to-peer processing means for establishing a communication connection; and a peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the first client; When peer-to-peer communication is being performed with one client, instead of the multicast receiving means receiving data, the peer-to-peer transmission / reception means receives peer-to-peer communication from the first client. Activating the second client to receive data transmitted by peer communication It is also achieved by that data communication program.

  The data to be transmitted / received is basically audio data, but it is also possible to transmit / receive image data or the like as necessary.

  According to the present invention, there are provided a data communication method, a client, and a data communication program for realizing real-time communication in a serverless environment without complicating processing in a client and increasing network traffic. It becomes possible.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the present embodiment, the present invention is applied to realize an electronic conference system. FIG. 1 is a block diagram showing the overall configuration of the electronic conference system according to the present embodiment. As shown in FIG. 1, in the electronic conference system 10 according to the present embodiment, various clients are connected via a network 12.

  The electronic conference system 10 includes a first client 14 for an electronic conference organizer, and second clients 16-1, 16-2, 16-3,. The network 12 is a multicast network, and the first client 14 transmits data with the multicast address (MC address) as the destination, so that the second clients 16-1, 16-2,. Can transmit data. The second client can also perform peer-to-peer communication with the first client 14 by the operation of the participant. In FIG. 1, the second clients 16-1, 16-2 are communicating with the first client 14 on a peer-to-peer basis. On the other hand, the second clients 16-3 and 16-4 receive the data from the first client 14 by receiving the multicast address. Also, the second client (second client 16-5 in FIG. 1) connected to the non-multicast network (reference numeral 18) can receive the multicast address by tunneling.

  A microphone 20 and a speaker 22 are connected to the first client 14. The first client 14 has a display device (not shown) for displaying still images and moving images. The second client 16 (hereinafter simply denoted by reference numeral 16 except when indicating a specific second client) also has a display device. The second client is also connected to a speaker (not shown) that outputs audio data and a microphone (not shown) that accepts audio input from conference participants.

  For example, the audio data generated from the audio received by the organizer's microphone 20 is transmitted to the multicast address in the first client 14 through a mixing process described later. The second clients 16-3 to 16-5 receiving the multicast address output sound based on the received sound data from the speaker. Similarly, image data generated by the first client 14 and transmitted to the multicast address is also received by the second clients 16-3 to 16-5 receiving the multicast address, and the display device thereof. Etc. are displayed.

  FIG. 2 is a block diagram showing the configuration of the first client 14 according to the present embodiment. As shown in FIG. 2, a data input unit 30 that accepts audio from the microphone 20, a branch processing unit 32 that branches audio data when the peer-to-peer communication is to be performed, Mixing processing unit 34 for mixing audio data in the organizer, branching / mixing processing switch unit 36 for executing switching processing of the branching processing unit and mixing processing unit 34, and P2P processing unit for executing peer-to-peer communication processing 38, a packet receiving unit 40 for receiving a data packet from the address (speaker address) of the participant's second client, a packet transmitting unit 42 for transmitting a data packet addressed to the speaker address, and voice to the speaker 22 Data output unit 44 for output, multicast packet generator for generating packets such as multicast voice data 6, and has a multicast transmission unit 48 for transmitting a packet addressed to the multicast address.

  As shown in FIG. 3, the second client 16 includes a data input unit 50, a P2P processing unit 52, a packet transmission unit 56, a packet reception unit 58, a multicast reception unit 58 that receives packets from a multicast address, and a P2P processing unit. 52, and a data output unit 62 that outputs audio data output from the switch unit 60 to a speaker (not shown).

  Data communication and processing in the client when an electronic conference is realized by the first client 14 and the second client 16 configured as described above will be described.

  FIG. 4 is a flowchart showing a procedure at the start of the conference. In FIG. 4, two second clients are shown, but actually, between the second client and the first client operated by each person (participant) scheduled to participate in the conference. A similar exchange takes place.

  First, the first client 14 broadcasts a holding declaration to each of the second clients 16 using instant messaging (IM) (steps 400 and 401). Upon receiving the IM broadcast (step 402), the second client 16 of each participant transmits an IM reply indicating the participation state (presence) to the first client 14 (steps 403 and 404).

  When receiving the presence from each of the second clients 16, the first client 14 grasps the state of each of the second clients 16.

  Next, the first client 14 notifies the multicast (MC) address to each of the second clients 16 using IM (steps 406 and 407). When each of the second clients 16 receives the MC address, the second client 16 tunes the MC address (step 408) so that a packet transmitted to the MC address can be received. As a result, the conference can be held and the conference is started (step 409). Each of the second clients 16 waits for a packet to be transmitted to the multicast address (step 410). Here, the communication means used for the procedure from the meeting declaration to the standby (steps 400 to 410) is not limited to IM, but may be telephone, e-mail, or the like. For example, when e-mail is used, the organizer notifies the start of the conference by e-mail, and the participants prepare to receive the packet according to the above procedure. In this case, if a grouping function such as a mailing list is used, it is easy to notify the host of a specific group. In addition, the opportunity to hold the conference is not necessarily the organizer, and the organizer may accept the request from the participant and make a declaration of the event.

  The organizer's voice is received by the data input unit 30 via the microphone 20. As long as there is a request for speech from any of the participants and the organizer does not have permission to speak, the branch / mixing processing switch unit 36 sends the signal from the data input unit 30 to the mixing processing unit 34 side. The branch processing unit 32 is controlled so as to send, and the mixing processing unit 34 is controlled not to execute the mixing process of the voice data by the participant's speech and the voice data of the organizer.

  Therefore, the audio data from the data input unit 30 is transmitted to the multicast packet generation unit 46 via the branch processing unit 32 and the mixing processing unit 34. The multicast packet generator 46 packetizes the voice data, and the multicast transmitter transmits the generated packet to the multicast address.

  In the second client 16 receiving the multicast, the multicast receiving unit 58 receives the packet transmitted to the multicast address. During the multicast reception, the switch unit passes the data from the multicast reception unit 58 to the data output unit 62 as it is. Therefore, the packet received by the multicast receiving unit 58 is output from the data output unit 62 as voice data. As a result, the organizer's voice is reproduced in real time from a speaker (not shown) connected to the second client 16.

  In the second client, unless a speech request operation is performed, audio is reproduced based on the packet received by the multicast reception described above (see steps 500 and 501 in FIG. 5). In FIG. 5, such a second client is referred to as a second client (participant). On the other hand, in a certain second client, a participant may want to speak in a conference. In such a case, the participant operates the second client (step 502) and transmits a speech request to the first client 14 (step 503). Hereinafter, the second client operated by the participant who speaks in the conference is referred to as a second client (speaker).

  When the first client 14 receives a speech request from the second client (speaker), the first client 14 generates a response (speak permission) and returns a response signal to the second client (speaker) (step 504, 505). Thereby, multicasting is turned off in the second client (speaker) (step 506). When multicast is turned off, in the second client 14, the switch unit 60 passes the data from the P2P processing unit 52 to the data output unit 62.

  In addition, in the first client 14, the branch / mixing processing switch unit 36 is triggered by the generation of a speech permission response, and the audio data from the data input unit 30 is converted into the mixing processing unit 34 and the P2P. The data is passed through both of the processing units 38 (step 507). Further, the mixing processing unit 34 operates so as to mix both the voice data from the speaker who has passed through the P2P processing unit 38 and the voice data from the organizer that has passed through the branch processing unit 32. Depending on the timing of mixing, one of the voice data from the speaker or the voice data from the organizer may be silent data. In this case, the mixed data may be generated by mixing the silent data. It may be a process of discarding silence data.

  The first client 14 and the second client (speaker) each operate as described above to establish a peer-to-peer connection between them (step 508). In the first client 14, data transmission / reception via the P2P processing unit 38 is started (step 509). Similarly, in the second client (speaker), data transmission / reception via the P2P processing unit 52 is started (step 510).

  In the second client (speaker), when the speaker utters a voice toward a microphone (not shown), the data input unit 50 receives the voice data (voice data). The data input unit 50 outputs the audio data to the P2P processing unit 52. The P2P processing unit 52 outputs the audio data to the packet transmission unit 56 and also outputs it to the data output unit 62. From the data output part 62, the voice concerning a speaker's speech is output.

  The packet transmitter 56 packetizes the audio data and transmits it to the organizer address (that is, the address of the first client).

  When the packet reception unit 40 of the first client 14 receives a packet from the second client (speaker), the packet reception unit 40 outputs the received packet to the P2P processing unit 38 (step 511). . The voice data of the speaker based on the packet is transmitted to the mixing processing unit 34 via the P2P processing unit 38 and the branch / mixing switch unit 36. The mixing processing unit 34 is synthesized with the organizer's voice data from the data input unit 30 (step 512), and the synthesized voice data is packetized in the multicast packet generation unit 46, and the packet is sent to the multicast transmission unit. 48 is transmitted to the multicast address (step 513). In FIG. 7, arrows 701 to 703 indicate speaker voice data, arrows 704 indicate organizer voice data, and arrows 705 and 706 indicate synthesized voice data (or packets thereof).

  Therefore, the second client (participant) can reproduce the synthesized voice of the organizer's voice and the voice of the speaker by receiving the multicast address.

  On the other hand, peer-to-peer communication is realized between the second client (speaker) and the first client. Therefore, the organizer's voice data is transmitted to the packet transmission unit 42 via the branch processing unit 32, the branch / mixing processing switch unit 36, and the P2P processing unit 38, and the organizer's voice data is addressed to the speaker address. Packets are sent. In FIG. 8, the arrows indicate the transmission path of the organizer's audio data to the second client (speaker).

  As described above, according to the present embodiment, the synthesized voice of the organizer's voice and the voice of the speaker is transmitted to the second client (participant) to the multicast address. Therefore, the participant can hear the voices of both the organizer and the speaker. On the other hand, only the audio data of the organizer is transmitted to the second client (speaker) by peer-to-peer communication. In the second client (speaker), the voice data of the speaker himself is output to the data output unit 62 via the data input unit 50, the P2P processing unit 52, and the switch unit 60. That is, its own voice is emitted from the speaker in real time. The organizer's voice data is output to the data output unit 62 via the packet receiving unit 54, the P2P processing unit 52, and the switch unit 60, and emitted from the speaker. That is, the voice uttered by the participant himself / herself is once transmitted to the first client, and is not returned from the speaker after returning to the second client (speaker). For this reason, it is possible to prevent unnatural sound from the speaker due to the time lag of data transmission / reception.

  As shown in FIG. 6, when the speaker finishes speaking, the speaker operates the second client (speaker) and transmits a speech termination request to the first client 14 (steps 602 and 603). Note that multicast transmission / reception is continued between the first client 14 and the second client (participant) (steps 600 and 601).

  When the first client 14 receives the speech end request from the second client (speaker), the first client 14 generates a response (end permission) and returns a response signal to the second client (speaker) (step 604). 605), the second client (speaker) is released (step 606).

  Next, in the first client 14, the audio data from the data input unit 30 is passed only from the branch processing unit 32 to the mixing processing unit 34, and in the P2P processing unit 38, the second client ( Necessary processing is executed so that the voice data from the speaker is not processed (step 607). Thereby, the peer-to-peer connection between the first client 14 and the second client (speaker) is released, and transmission / reception of packets by the peer-to-peer is ended (steps 608 to 610).

  The second client (speaker) makes the multicast reception possible by the processing of the switch unit 60 or the like (step 611). As a result, the second client (speaker) receives the packet addressed to the multicast address from the first client 14 in the same manner as the other second client (participant), and transmits the voice to the speaker (FIG. (Step 612 to step 616).

  In the present embodiment, a one-to-many conference mode is basically used between the organizer and the participants, so that only the organizer's terminal (first client) performs multicast transmission. The participant terminal (second client) basically maintains the multicast reception state. When the participant speaks, the second client (speaker) notifies the address of the first client of the intention to speak, and after permission of the organizer, the second client (speaker) peers with the first client. • Start two-peer communication.

  Therefore, packets are transmitted and received in peer-to-peer communication only between the second client (speaker) and the first client 14, and the other second clients (participants) are the first clients. 14 receives a packet transmitted from the address 14 to the multicast address. Therefore, the amount of packets transmitted between the first client and the second client can be reduced, and traffic on the network can be suppressed.

  In addition, since the peer-to-peer communication is performed only with the second client (speaker) in the first client, an increase in the load on the first client can be minimized. Become. Furthermore, since mixing of audio data only needs to be performed by the first client, clients other than the first client (that is, the second client) are not required to have high performance, and the client cost can be reduced. Is possible.

  The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in the above embodiment, the voice data based on the voice of the speaker in the electronic conference is mixed with the voice data of the organizer in the first client and transmitted to the multicast address. However, the present invention is not limited to this. However, the present invention can also be applied to image data. In this case, the second client (participant) sends image data including both the organizer image and the speaker image (for example, the right half of the image is the organizer image and the left half is the speaker. Image) is generated in the mixing processing unit 34, and the packet of the image data is transmitted to the multicast address. Also, audio data and image data may be mixed.

Furthermore, although the case where there is a single second client (speaker) has been described in the above embodiment, there may be a plurality of second clients (speakers). In this case,
For the audio data transmitted by the P2P processing unit 38 of the first client 14 through peer-to-peer communication with a certain second client (speaker), the audio data of the organizer, the certain second data The voice data transmitted from the second client (speaker) other than the client (speaker) is synthesized. As a result, the voice data of the voice in which the organizer and the voice of another speaker are synthesized is transmitted from the first client to a certain second client (speaker) by peer-to-peer communication. .

  Furthermore, the second client operated by a person who does not speak (for example, an observer) in the conference only needs to be able to receive only the multicast.

FIG. 1 is a block diagram showing the overall configuration of the electronic conference system according to the present embodiment. FIG. 2 is a block diagram showing the configuration of the first client according to this exemplary embodiment. FIG. 3 is a block diagram showing the configuration of the second client according to the present embodiment. FIG. 4 is a flowchart showing a procedure at the start of the conference in the present embodiment. FIG. 5 is a flowchart showing a procedure when a speech request is received from a participant in the present embodiment. FIG. 6 is a flowchart showing a procedure when there is a speech end request from a participant in the present embodiment. FIG. 7 is a diagram illustrating a flow of data that is multicast when a speaker speaks. FIG. 8 is a diagram illustrating a flow of data transmitted to the second client operated by the speaker when the speaker speaks.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Network 14 1st client 16 2nd client 30 Data input part 32 Branch processing part 34 Mixing process part 36 Branching / mixing process switch part 38 P2P processing part 40 Packet receiving part 42 Packet transmitting part 44 Data output part 46 For multicast Packet generation unit 48 Multicast transmission unit 50 Data input unit 52 P2P processing unit 54 Packet reception unit 56 Packet transmission unit 58 Multicast reception unit 60 Switch unit 62 Data output unit

Claims (10)

A data communication method between a first client and one or more second clients, each connected via a network, comprising:
Accepting data input to the first client at the first client and transmitting the data to a multicast address;
Receiving each of the data from a multicast address at each of the second clients;
When the first client receives a speech request from the second client, it establishes a peer-to-peer communication connection with the caller's second client for the speech request. Steps,
The first client receives data transmitted by peer-to-peer communication from the caller's second client, the data input to the first client, and the caller's second client Combining the data received from the client;
And a step of transmitting the synthesized data to a multicast address in the first client. When a peer-to-peer communication connection is established between the caller's second client and the first client,
Transmitting, in the first client, data input to the first client by peer-to-peer communication to the caller's second client;
Receiving the data transmitted from the first client by peer-to-peer communication instead of receiving from the multicast address at the second client of the caller. The data communication method according to claim 1. When there are a plurality of second clients of the caller, in the first client, the second client of the certain caller, the data input to the first client, and the caller's second client Combining data of a second client of a caller other than the second client;
3. The step of transmitting the combined data by peer-to-peer communication to the second client of the certain caller at the first client. The data communication method described in 1. When the second client is connected to another network that does not support multicast, the second client receives the data from the multicast address by a virtual network connection by tunneling from the network. The data communication method according to any one of claims 1 to 3, wherein the data communication method is performed. A first client connected to a second client via a network,
A multicast transmission means for accepting input data and transmitting the data to a multicast address;
A peer-to-peer processing means for establishing a peer-to-peer communication connection with a caller's second client in response to a speech request from the second client;
Peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the caller's second client;
Combining processing means for combining the data received from the second client of the caller and the input data;
The first client, wherein the multicast transmission means transmits data from the combining processing means to a multicast address. When the peer-to-peer processing means includes a plurality of second clients of the caller, the data input to the first client is transmitted to the second client of the caller, and the certain call is transmitted. The data of the second client of the caller other than the second client of the sender,
6. The first client according to claim 5, wherein the peer-to-peer transmission / reception means transmits the combined data to the second client of the certain caller. A second client connected to the first client via a network,
Multicast receiving means for receiving data transmitted from the first client to a multicast address;
Peer-to-peer processing means for establishing a peer-to-peer communication connection with the first client;
Peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the first client,
When peer-to-peer communication is being performed with the first client, instead of the multicast receiving means receiving data, the peer-to-peer transmission / reception means receives a peer from the first client. A second client that receives data transmitted by two-peer communication. A data communication program readable by a first client connected to a second client via a network, wherein the first client is
A multicast transmission means for accepting input data and transmitting the data to a multicast address;
A peer-to-peer processing means for establishing a peer-to-peer communication connection with a second client of a caller involved in the speech request in response to a speech request from the second client;
Peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the second client of the caller; and
Function as a synthesis processing means for synthesizing the data received from the second client of the caller and the input data;
A data communication program characterized in that the multicast transmission means operates the first client so as to transmit data from the synthesis processing means to a multicast address. When making the first client function as a peer-to-peer processing means, when there are a plurality of the second clients of the caller, the caller's second client is transferred to the first client. The first client to synthesize the data entered into the data of the second client of the caller other than the second client of the certain caller;
When the first client is caused to function as the peer-to-peer transmission / reception means, the combined data is transmitted to the second client of the certain caller. The data communication program according to claim 8, wherein the client is operated. A data communication program readable by a second client connected to a first client via a network, wherein the second client is
Multicast receiving means for receiving data transmitted from the first client to a multicast address;
Peer-to-peer processing means for establishing a peer-to-peer communication connection with said first client; and
Functioning as a peer-to-peer transmission / reception means for performing data transmission / reception by peer-to-peer communication with the first client;
When peer-to-peer communication is being performed with the first client, instead of the multicast receiving means receiving data, the peer-to-peer transmission / reception means receives a peer from the first client. A data communication program for operating the second client so as to receive data transmitted by two-peer communication.

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