JP5959428B2 - Broadcast receiving method, system, terminal, and program for intercepting data packet received by one terminal at the other terminal - Google Patents

Description

  The present invention relates to a technique for broadcasting from an access point to a plurality of terminals within a local network.

  One access point is connected to a WAN (Wide Area Network), and the other is connected to a wireless LAN (Local Area Network). Then, the access point relays data packets transmitted / received between the server and the terminal. The access point is also generally equipped with a DHCP (Dynamic Host Configuration Protocol) function for assigning an IP address to each terminal.

  Access points are commercially available at a low price, and anyone can easily install them. If installed in a company or store, a large number of terminals such as smartphones and personal computers can be simultaneously connected to the access point. The access point executes an authentication sequence with the terminal and establishes a communication link. Therefore, the number of allowable connections that a terminal can connect to the access point is limited due to the processing capability of the access point. Some commercially available general access points can connect from about 14 terminals to a maximum of about 50 terminals. For example, some access points installed for connection from smartphones by communication carriers can connect up to about 100 terminals at the maximum. For this reason, even if the access point transmits the same data packet (content), it cannot be transmitted to a terminal having an allowable number of connections or more.

  Also, in a wireless LAN between an access point and a plurality of terminals, an available bandwidth is defined. Specifically, in the case of 802.11a / g, the available bandwidth is 54 Mbps, and no more data packets can be transmitted. Then, even if the access point is connected to only terminals that are less than or equal to the allowable number of connections, the access point cannot transmit data packets beyond the available bandwidth. That is, the number of terminals that can be connected to the access point may be further limited.

  On the other hand, there is a multicast method for the access point to broadcast the same data packet to a large number of terminals. According to the “multicast” method, a multicast address for the same data packet is set, and the terminal joins / leaves the multicast address. Many terminals participating in the multicast address can simultaneously receive the same data packet. By using the multicast method, a large number of terminals can receive the same data packet in a broadcast manner with only a minimum bandwidth guarantee in the LAN.

WildPackets, Gigazine, “Free Wireless LAN Packet Capture“ Omnipeek Personal ”Operable on Windows”, [online], [Search September 10, 2012], Internet <URL: http://gigazine.net/ news / 20071202_omnipeek_personal / ＞ "Wireshark", [online], [Search September 10, 2012], Internet <URL: http://www.simeji.com/wiki/index.php?Wireshark>

  However, access points and terminals that support the multicast method are not commonly used. In addition, a multicast address detection and joining / leaving sequence are separately required between the terminal and the access point. On the other hand, the multicast method is considered suitable for distributing data in an event to a specific terminal group within a specific communication area and in a specific time zone. It is difficult to deal with terminals.

  Therefore, the present invention allows a large number of terminals to broadcast the same data packet without using a multicast scheme and without being limited by the allowable number of terminals connected to an access point or the usable bandwidth of a wireless LAN. It is an object to provide a method and system capable of receiving.

According to the present invention, broadcast reception in a system having a content distribution server that distributes content, an access point that receives the content and relays it to the local network, and a plurality of terminals that receive the content via the local network A method,
A first step in which a first terminal establishes a communication connection with a content distribution server via an access point;
A second step in which the first terminal receives a data packet of the content from the content distribution server via the access point and responds to the content distribution server with a confirmation packet with an interception permission flag;
A third step in which a second terminal intercepts a confirmation packet to which an interception permission flag is added, flowing in a local network between the first terminal and the access point;
When the second terminal intercepts the confirmation packet with the interception permission flag added, the data packet flowing from the access point to the first terminal is intercepted without establishing a communication connection with the content distribution server. And a fourth step of receiving.

According to another embodiment of the broadcast receiving method of the present invention,
The communication connection is based on the TCP (Transmission Control Protocol) layer,
The confirmation packet is preferably a TCP ACK packet.

  According to another embodiment of the broadcast receiving method of the present invention, the interception permission flag is preferably a specific value that means interception permission described in the Reserved portion of the ACK header of the TCP header.

According to another embodiment of the broadcast receiving method of the present invention,
For the third step, the second terminal
When a confirmation packet with an interception permission flag is intercepted, the content identification information included in the data packet corresponding to the confirmation packet is clearly indicated to the user via the user interface,
It is also preferable to start receiving a data packet flowing from the content distribution server to the first terminal after the user performs an operation for requesting the content based on the content identification information on the user interface.

  According to another embodiment of the broadcast receiving method of the present invention, when the second terminal starts receiving the data packet flowing from the content distribution server to the first terminal for the third step, the player program It is also preferable to start automatically.

According to the present invention, there is provided a broadcast receiving system having a content distribution server for distributing content, an access point for receiving the content and relaying it to the local network, and a plurality of terminals for receiving the content via the local network. There,
The first terminal is
A communication connection establishing means for establishing a communication connection with the content distribution server via the access point;
A data packet receiving means for receiving a content data packet from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag;
The second terminal
A confirmation packet interception means for intercepting a confirmation packet with an interception permission flag added, which flows in the local network between the first terminal and the access point;
Data packet interception reception that intercepts data packets flowing from the access point to the first terminal without establishing a communication connection with the content distribution server when intercepting a confirmation packet with an interception permission flag added Means.

According to the present invention, there is provided a broadcast receiving program for causing a computer installed in a terminal that receives content from a content distribution server and communicates with an access point that relays to a local network to communicate with the local network,
As an interceptor function,
A communication connection establishing means for establishing a communication connection with the content distribution server via the access point;
A data packet receiving means for receiving a content data packet from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag;
As an intercept function,
A confirmation packet interception means for intercepting a confirmation packet with an interception permission flag added, which flows in the local network between the first terminal and the access point;
Data packet interception reception that intercepts data packets flowing from the access point to the first terminal without establishing a communication connection with the content distribution server when intercepting a confirmation packet with an interception permission flag added And the computer is made to function so as to have a means.

According to the present invention, in an intercepting terminal that establishes a communication connection with a content distribution server via an access point connected to a local network,
A data packet receiving means for receiving a data packet of the content from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag;
By allowing other terminals connected to the local network to intercept the confirmation packet with the interception permission flag added, the data packet flowing from the access point to the intercepting source terminal is operated to be intercepted. To do.

According to the present invention, together with the above-described intercepting terminal, an intercepting terminal connected to the local network,
A confirmation packet interception means for intercepting a confirmation packet with an interception permission flag flowing in a local network between the intercepting terminal and the access point;
Data packet interception reception that intercepts data packets flowing from the access point to the first terminal without establishing a communication connection with the content distribution server when intercepting a confirmation packet with an interception permission flag added Means.

According to the present invention, in a program for causing a computer installed in an intercepting terminal to establish a communication connection with a content distribution server via an access point connected to a local network,
Receiving the content data packet from the content distribution server via the access point, and causing the computer to function as a data packet receiving means for responding to the content distribution server with a confirmation packet with an interception permission flag added thereto,
By allowing other terminals connected to the local network to intercept the confirmation packet with the interception permission flag added, the data packet flowing from the access point to the intercepting source terminal is operated to be intercepted. To do.

According to the present invention, together with the above-described interception source terminal, a program for causing a computer mounted on an interception destination terminal connected to the local network to function,
A confirmation packet interception means for intercepting a confirmation packet with an interception permission flag flowing in a local network between the intercepting terminal and the access point;
Data packet interception reception that intercepts data packets flowing from the access point to the first terminal without establishing a communication connection with the content distribution server when intercepting a confirmation packet with an interception permission flag added Means.

  According to the broadcast receiving method, system, terminal, and program of the present invention, a large number can be used without using a multicast method and without being limited by the allowable number of terminals connected to an access point and the available bandwidth of a wireless LAN. Can receive the same data packet by broadcast.

It is a system configuration diagram in the present invention. It is a sequence diagram in the present invention. It is explanatory drawing showing the TCP frame format of the confirmation packet responded from a terminal. It is a function block diagram of the terminal in this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram according to the present invention.

  The system of FIG. 1 includes a content distribution server 2 that distributes content, an access point 3 that receives the content and relays it to the wireless LAN, and a plurality of terminals 1 (clients) that receive the content via the wireless LAN. Have. The content distribution server 2 and the access point 3 are existing, and according to the present invention, the software functions installed in the terminal 1 are characterized. The terminal 1 is, for example, a tablet terminal, a smartphone, or a personal computer.

  According to FIG. 1, the terminal 1 </ b> A functions as a base terminal and establishes a communication link with the access point 3 via the wireless LAN. Thereafter, the terminal 1A further establishes a communication connection with the content distribution server 2 via the access point 3. Accordingly, the terminal 1A can receive the data packet based on the content from the content distribution server 2 via the access point 3. On the other hand, the other terminals 1 </ b> B and 1 </ b> C have not established a communication link with the access point 3. According to the present invention, the terminals 1B and 1C receive broadcast data by intercepting data packets received from the content distribution server 2 by the terminal 1A.

  The system shown in FIG. 1 is preferably applied to a public wireless LAN such as a stadium, a concert hall, or a shopping center. Using a smartphone or tablet terminal that the user owns, content (for example, advertisement video data or coupon information) related to an event or shopping can be broadcasted from an access point. Specifically, it can be applied to services such as area limited 1Seg, Ustream (registered trademark), NicoNico Live Broadcast (registered trademark), radiko (registered trademark), and Lismo wave (registered trademark).

  According to the present invention, it is necessary that a dedicated application program is installed and activated in each of the terminal 1A serving as a base terminal and the terminals 1B and 1C that intercept data packets.

  FIG. 2 is a sequence diagram in the present invention.

[S1] First, the terminal 1A scans a beacon signal broadcast from the access point 3. When the terminal 1A receives the beacon signal, the terminal 1A transmits a connection request based on an SSID (Service Set Identifier) included in the beacon signal to the access point 3. The terminal 1A stores a password for the SSID in advance, and also includes the password in the connection request. On the other hand, the access point 3 returns a connection response to the terminal 1A. The access point 3 also has a DHCP function, and transmits an IP address assignment notification to the terminal 1A. In this way, the terminal 1A establishes a communication link with the access point 3. Thereafter, the terminal 1A establishes a communication connection with the content distribution server 2 via the access point 3. This communication connection is for one-to-one unicast communication based on the TCP (Transmission Control Protocol) layer.

  According to the present invention, it is not necessary until the terminal 1A reproduces the content received from the content distribution server 2 by the player program. It is only necessary that the data packet flows from the access point 3 to the terminal 1A.

[S2] The terminal 1A transmits a request message for the content desired by the user to the content distribution server 2. On the other hand, the content distribution server 2 transmits the content to the terminal 1A via the access point 3. According to the present invention, when distributing content such as video and audio, it is considered that the streaming method, rather than the file download method, can take advantage of the broadcast reception feature.

  According to TCP, the terminal 1A returns a confirmation packet (ACK packet) to the content distribution server 2 every time it receives a certain amount of data packets. Here, the user of the terminal 1 </ b> A as the base terminal can be permitted to intercept the data packet received by the other terminal in the wireless LAN. In this case, an “interception permission flag” is added to the confirmation packet of the present invention. That is, the interception permission flag here means that the terminal 1A permits the data packet received by itself to be intercepted by the other terminals 1B and 1C. The interception permission flag is a unique identifier included in the ACK of the TCP header.

  FIG. 3 is an explanatory diagram showing the TCP frame format of the confirmation packet returned from the terminal.

  According to the present invention, “Reserved part of acknowledgment number of ACK of TCP header” is used as the interception permission flag. According to TCP, the bit length of ACK is 32 bits, and an acknowledgment number (Acknowledgement Number) is included as a sequence number of a data packet to be transmitted next by the transmission side. As a result, if this number and the sequence number of the data packet to be transmitted next are the same, the transmitting side can determine that the previously transmitted data packet has been normally received. Further, a reserved part (6 bits) that can be expanded in the future is included in the part of the acknowledgment number of the ACK. Therefore, the reserved part of the ACK includes a specific number indicating interception permission as an interception permission flag, so that it is recognized by another terminal that intercepts the packet. Normally, “Reserved” stores 0 (000000) and is not used at present. Therefore, a specific interception permission flag may be “111111”.

  Note that the confirmation packet including the interception permission flag based on the two embodiments is transmitted to the content distribution server 2. The content distribution server 2 also recognizes that a data packet to be transmitted to the terminal itself can be intercepted by looking at the interceptable flag. On the other hand, when the content distribution server 2 detects the interceptable flag even though it is not the content that should originally be broadcast, the transmission of the data packet can be stopped.

[S3] The terminals 1B and 1C sniff packets that flow on the wireless LAN between the terminal 1A and the access point. Here, the confirmation packet for the data packet does not permit the interception of only the data packet, but permits the interception of a series of data packets following the confirmation packet. Therefore, the identification based on the interception of the TCP ACK packet need only identify the first fixed amount of packets (for example, the first five packets started to be received) from which the terminal 1B has started receiving the communication. It is not necessary to identify all of the large number of confirmation packets flowing through the wireless LAN.

  Here, as an “interception” method in the terminals 1B and 1C, an existing IP packet capture method is used (for example, see Non-Patent Documents 1 and 2). According to these capture methods, even if a data packet is encrypted with WEP or the like (Wired Equivalent Privacy), it can be captured by inputting a valid WEP key.

  Then, the terminals 1B and 1C automatically start an application such as a media player, for example, when detecting the packet with the interception permission flag added. As a result, the intercepted data packet transmitted from the access point 3 to the base terminal 1A can be reproduced as a data packet received by the media player. Note that the terminals 1B and 1C have a function of removing the destination (terminal 1A) specified on the data packet and reproducing it on the media player as being permitted to be reproduced on the own terminal.

  Optionally, when the terminals 1B and 1C intercept the confirmation packet with the interception permission flag added, the contents identification information included in the data packet corresponding to the confirmation packet is clearly indicated to the user via the user interface. It is also preferable. The terminals 1B and 1C inquire of the user interface whether or not to receive an interceptable data packet. After the user performs an operation of desiring to receive content based on the content identification information, the intercepted reception of the data packet flowing from the content distribution server 2 to the terminal 1A is started.

[S4] When the terminals 1B and 1C intercept the confirmation packet to which the interception permission flag is added, the data packets flowing from the access point 3 to the terminal 1A are intercepted. At this time, the terminals 1B and 1C do not establish a communication link with the access point 3, and do not establish a communication connection with the content distribution server 2. Terminals 1B and 1C only receive data packets transferred from access point 3 to terminal 1A by interception. The data packet received by interception is reproduced by the media player and viewed by the users of the terminals 1B and 1C.

  Interception enables broadcast reception within the wireless LAN without giving any load to the processing capability of the access point 3 and the bandwidth of the wireless LAN and the Internet. In particular, interception does not affect the allowable number of terminals connected to the access point 3.

The content file size, bit rate, and the like are set values of the content transmitted from the content distribution server 2. The buffer capacity at the time of reproduction depends on the installed media player. For example, in the case of video and audio, several tens of frames are transmitted per second.

  Further, when the terminals 1B and 1C are intercepted from the middle of the content, the terminals 1B and 1C can be reproduced from the received data packet as needed. In order for the terminals 1B and 1C to play back from the top data packet of the content, it is preferable that the media player is activated in advance and set in the intercept standby state by the intercept function.

  Furthermore, as another embodiment, the data packet flowing from the access point 3 to the terminal 1A may be encrypted (for example, WEP, WPA-PSK (Wi-Fi Protected Access Pre-Shared Key)). The terminal 1A holds a key for the SSID in advance. Similarly, the intercepting terminals 1B and 1C need to hold a key for the SSID in advance. However, an encryption protocol that requires establishing a communication link with the access point 3, such as WPA2 or EPA, cannot be used.

  FIG. 4 is a functional configuration diagram of a terminal according to the present invention.

  According to FIG. 4, the terminal 1 has an intercept function as a base terminal, and an intercept function that intercepts and receives data packets. The intercept function includes a communication connection establishment unit 111, a data packet reception unit 112, and a data packet transmission unit 113. These functional components are realized by executing a program that causes a computer installed in the terminal to function. The program in the present invention may be a broadcast receiving program that integrally includes both the intercept function and the intercept function, or may be separate from the intercept terminal program and the intercept terminal program. .

  The communication connection establishment unit 111 is an existing function, and establishes a communication connection with the content distribution server via the access point (see S1 described above).

  The data packet receiving unit 112 receives a data packet of content from the content distribution server 2 via the access point 3 and responds to the content distribution server with a confirmation packet with an interception permission flag added (see S2 described above).

  The data packet transmission unit 113 is an existing function and transmits some data packet to the content distribution server 2.

  As the interception destination function, a confirmation packet interception unit 121 and a data packet interception reception unit 122 are provided. These functional components are realized by executing a program that causes a computer installed in the terminal to function.

  The confirmation packet interception unit 121 intercepts the confirmation packet with the interception permission flag added, which flows in the local network between the terminal 1A and the access point (see S3 described above).

  The data packet interception receiving unit 122 intercepts the data packet flowing from the access point to the terminal 1A without establishing a communication connection with the content distribution server when intercepting the confirmation packet with the interception permission flag added. Receive (see S4 described above).

  As described above in detail, according to the broadcast receiving method, system, terminal, and program of the present invention, the number of allowable connections of the terminal to the access point and the usable bandwidth of the wireless LAN can be achieved without using the multicast method. Regardless of the width, a large number of terminals can broadcast the same data packet. According to the present invention, a large number of terminals in a LAN can receive data packets in a broadcast manner without imposing a load on the processing capability of the access point and the transmission path of the LAN or the Internet. At this time, there is no limit on the number of receivable terminals.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

DESCRIPTION OF SYMBOLS 1 Terminal 10 Communication interface 111 Communication connection establishment part 112 Data packet receiving part 113 Data packet transmission part 121 Confirmation packet interception part 122 Data packet interception reception part 13 Application processing part 2 Content delivery server 3 Access point

Claims (11)

A broadcast receiving method in a system comprising a content distribution server for distributing content, an access point for receiving the content and relaying it to a local network, and a plurality of terminals for receiving the content via the local network ,
A first step in which a first terminal establishes a communication connection with the content distribution server via the access point;
A second step in which a first terminal receives a data packet of content from the content distribution server via the access point and responds to the content distribution server with a confirmation packet with an interception permission flag;
A third step in which a second terminal intercepts the confirmation packet to which the interception permission flag is added, which flows in a local network between the first terminal and the access point;
The second terminal flows from the access point to the first terminal without establishing a communication connection with the content distribution server when the confirmation packet with the interception permission flag added is intercepted. And a fourth step of receiving a data packet by interception. The communication connection is based on a TCP (Transmission Control Protocol) layer,
The broadcast receiving method according to claim 1, wherein the confirmation packet is a TCP ACK packet.   3. The broadcast receiving method according to claim 2, wherein the interception permission flag is a specific value that means interception permission described in a Reserved portion of an ACK header of a TCP header. For the third step, the second terminal
When intercepting the confirmation packet with the interception permission flag added, the content identification information included in the data packet corresponding to the confirmation packet is clearly indicated to the user via a user interface,
The reception of the data packet flowing from the content distribution server to the first terminal is started after the user performs an operation for requesting reception of the content based on the content identification information on the user interface. Item 4. The broadcast receiving method according to any one of Items 1 to 3.   The second terminal automatically starts a player program when starting to receive the data packet flowing from the content distribution server to the first terminal in the third step. 5. The broadcast receiving method according to any one of items 1 to 4. A broadcast receiving system comprising a content distribution server for distributing content, an access point for receiving the content and relaying it to a local network, and a plurality of terminals for receiving the content via the local network,
The first terminal is
Communication connection establishment means for establishing a communication connection with the content distribution server via the access point;
Data packet receiving means for receiving a data packet of content from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag added thereto,
The second terminal
Confirmation packet interception means for intercepting the confirmation packet with the interception permission flag flowing in a local network between the first terminal and the access point;
When the confirmation packet with the interception permission flag added is intercepted, the data packet flowing from the access point to the first terminal is received by intercepting without establishing a communication connection with the content distribution server. And a data packet interception receiving means. A broadcast receiving program for functioning a computer mounted on a terminal that receives content from a content distribution server and relays it to a local network and a terminal that communicates via the local network,
As an interceptor function,
Communication connection establishment means for establishing a communication connection with the content distribution server via the access point;
Data packet receiving means for receiving a data packet of content from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag added thereto,
As an intercept function,
Confirmation packet interception means for intercepting the confirmation packet with the interception permission flag flowing in a local network between the first terminal and the access point;
When the confirmation packet with the interception permission flag added is intercepted, the data packet flowing from the access point to the first terminal is received by intercepting without establishing a communication connection with the content distribution server. A broadcast reception program for a terminal, which causes a computer to function so as to have a data packet interception reception unit. In the intercepting terminal that establishes a communication connection with the content distribution server via an access point connected to the local network,
A data packet receiving means for receiving a data packet of content from the content distribution server via the access point and responding to the content distribution server with a confirmation packet with an interception permission flag;
An operation is performed to cause the other terminal connected to the local network to receive the data packet flowing from the access point to the intercepting terminal by intercepting the confirmation packet with the interception permission flag added thereto. Interceptor terminal characterized by letting An intercepting terminal connected to a local network together with the intercepting terminal according to claim 8,
Confirmation packet intercepting means for intercepting the confirmation packet with the interception permission flag flowing in a local network between the intercepting terminal and the access point;
When the confirmation packet with the interception permission flag added is intercepted, the data packet flowing from the access point to the first terminal is received by intercepting without establishing a communication connection with the content distribution server. And a data packet intercepting and receiving means. In a program for functioning a computer mounted on an intercepting terminal that establishes a communication connection with a content distribution server via an access point connected to a local network,
Receiving a data packet of content from the content distribution server via the access point, and causing a computer to function as a data packet receiving means for responding to the content distribution server with a confirmation packet with an interception permission flag;
An operation is performed to cause the other terminal connected to the local network to receive the data packet flowing from the access point to the intercepting terminal by intercepting the confirmation packet with the interception permission flag added thereto. A program for an eavesdropping terminal, characterized by A program for causing a computer mounted on an intercepting terminal connected to a local network to function together with the intercepting terminal according to claim 8,
Confirmation packet intercepting means for intercepting the confirmation packet with the interception permission flag flowing in a local network between the intercepting terminal and the access point;
When the confirmation packet with the interception permission flag added is intercepted, the data packet flowing from the access point to the first terminal is received by intercepting without establishing a communication connection with the content distribution server. And a data packet intercepting / receiving means.

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