JP2015119217A - Communication system and terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable direct communication between two terminals even in a case where a NAT router that performs different transmission source port number conversion when only a destination port number is changed is interposed.SOLUTION: In a communication system, terminals (PC1 and PC2) subordinate to an NAT router communicate with each other by using a transmission source address, a transmission source port number, a destination address, and a destination port number. The PC1, PC2 transmits data to a server to notify the partner side PC2, PC1 of the transmission source port number. The server notifies the PC2, PC1 of a port number based on the transmission source port number used for the data transmission by the PC1, PC2. The PC1, PC2 uses a transmission source port number different from the transmission source port number used for the data transmission to the server, and transmits data by using a port number based on the received port number related to the PC2, PC1 as a destination port number to try to connect with the PC2, PC1.

Description

  The present invention relates to a communication system and a terminal device that perform direct communication between terminal devices under the control of separate NAT routers connected to a wide area communication network such as the Internet.

  2. Description of the Related Art Conventionally, network session systems that enable musical sessions such as musical instrument performance (ensemble) and duet chorus via a wide-area communication network such as the Internet are known. In this session system, performance information based on the performance of its own terminal is transmitted to other terminals via a wide-area communication network so that each terminal can play musical sounds of both terminals. When the performance information is communicated directly between a plurality of terminals without going through a server when it is under the network address translation (NAT) router (local side), the NAT router must be exceeded. There is.

  The NAT technology is described in “RFC 4787” of Non-Patent Document 1 below. RFC4787 is a technical specification published by IETF (Internet Engineering Task Force), and describes NAT characteristics related to NAT traversal in unicast UDP. As NAT router behavior, three patterns of endpoint-independent mapping, address-dependent mapping, and address & port number-dependent mapping are generally well known. Therefore, the behavior patterns of these three NAT routers will be mentioned. FIG. 1A to FIG. 1C are diagrams for explaining the behavior pattern of a NAT router. Inside the above three NAT routers, from a transmission source terminal such as a PC (personal computer) under the NAT router, When transmission is performed using the same combination of “source address: 192.168.0.1” and “source port number: 5000”, the source address and the source port number are as shown in FIGS. 1A to 1C. Converted.

http://www.ietf.org/rfc/rfc4787.txt

  In pattern 1 of FIG. 1A, when a packet is transmitted from the subordinate of the NAT router using the same source address and source port number, the same port number conversion is performed regardless of the destination address and destination port number. The behavior of the type of NAT router is shown, and is defined as “endpoint-independent mapping” in RFC4787. In this pattern 1, in the case of the left side of the figure, “destination address: 2.2.2.2” using “source address: 192.168.0.1” and “source port number: 5000”. In the example, packet 1 is transmitted from PC 1 to the server by transmitting packet 1 to “destination port number: 5000”. In the case of the center in the figure, “source address: 192.168.0.1” and “source port number: 5000” are used, and “destination address: 2.2.2.2” and “destination port number” are used. : 2 is transmitted to the server by transmitting packet 2 to “5001”. In the case of the right side of the figure, “destination address: 3.3.3.3” and “destination port number” are used by using “source address: 192.168.0.1” and “source port number: 5000”. : Packet 5000 is transmitted to PC2 by transmitting packet 3 to “5000”. In these cases, the NAT router under the control of PC1 converts the same source port number because the same source address and source port number are used even if the destination address and destination port number are different. In the transmission of all packets 1 to 3, for example, “transmission source address: 192.168.0.1” and “transmission source port number: 5000” are “transmission source address: 1.1.1.1 and transmission”. Original port number: 20000 ". Note that “source address: 192.168.0.1” and “source port number: 5000” are local addresses, and “source address: 1.1.1.1” and “source port number: “20000”, “destination address: 2.2.2.2” and “destination port number: 5000”, “destination address: 2.2.2.2” and “destination port number: 5001”, and “destination address: “3.3.3.3” and “destination port number: 5000” are global addresses. The same applies to the local address and the global address as will be described later.

  Pattern 2 in FIG. 1B shows the behavior of a NAT router of a type that performs different port number conversion when the destination address changes when a packet is transmitted from the subordinate of the NAT router using the same source address and source port number. RFC4787 defines “address-dependent mapping”. In this case, the source port number is converted sequentially (that is, “+1” is added to the previous conversion result). In this pattern 2, in the case of the left side of the figure, “destination address: 2.2.2.2” using “source address: 192.168.0.1” and “source port number: 5000”. In the example, packet 1 is transmitted from the PC 1 to the server by transmitting the packet 1 to the “destination port number 5000”. In the case of the center in the figure, “source address: 192.168.0.1” and “source port number: 5000” are used, and “destination address: 2.2.2.2” and “destination port number” are used. : 2 is transmitted to the server by transmitting packet 2 to “5001”. In the case of the right side of the figure, “destination address: 3.3.3.3” and “destination port number” are used by using “source address: 192.168.0.1” and “source port number: 5000”. : Packet 5000 is transmitted to PC2 by transmitting packet 3 to “5000”. In these cases, if the NAT router under the control of PC1 has different destination addresses, it converts different source port numbers even if the same source address and source port number are used. "Transmission source address: 192.168.0.1" and "Transmission source port number: 5000" are converted into "Transmission source address: 1.1.1.1 and Transmission port number: 20000" respectively. In transmission of packet 3, “source address: 192.168.0.1” and “source port number: 5000” are “source address: 1.1.1.1 and source port number: 20001”. Is converted to.

  Pattern 3 in FIG. 1C is a type of NAT that performs different port number conversion only when either the destination address or the destination port number changes when transmitting using the same source address and source port number from under the NAT. This shows the behavior of the router, and is defined as “address & port number dependent mapping” in RFC4787. Also in this case, the source port number is converted sequentially (that is, “+1” is added to the previous conversion result). In this pattern 3, in the case of the left side of the figure, “destination address: 2.2.2.2” using “source address: 192.168.0.1” and “source port number: 5000”. In the example, packet 1 is transmitted from the PC 1 to the server by transmitting the packet 1 to the “destination port number 5000”. In the case of the center in the figure, “source address: 192.168.0.1” and “source port number: 5000” are used, and “destination address: 2.2.2.2” and “destination port number” are used. : 2 is transmitted to the server by transmitting packet 2 to “5001”. In the case of the right side of the figure, “destination address: 3.3.3.3” and “destination port number” are used by using “source address: 192.168.0.1” and “source port number: 5000”. : Packet 5000 is transmitted to PC2 by transmitting packet 3 to “5000”. In these cases, if one of the destination address and the destination port number is different, the NAT router under the control of PC1 performs conversion of a different source port number even if the same source address and source port number are used. For example, in transmission of the packet 1, “source address: 192.168.0.1” and “source port number: 5000” are “source address: 1.1.1.1 and source port number: 20000”. In the transmission of the packet 2, “source address: 192.168.0.1” and “source port number: 5000” are “source address: 1.1.1.1 and source port” Number: 20001 ", and in transmission of packet 3," source address: 192.168.0.1 "and" source port number: 5000 " Source address: 1.1.1.1 and the source port number: 20002 is converted to ".

  By the way, when direct communication is performed between two terminals under the NAT router in this way, the conversion is performed under the influence of the source address and source port number conversion by each NAT router described above. Both terminals cannot be connected without knowing the address and port number in some way.

  For example, the terminal PC1 under the NAT router 1 and the terminal PC2 under the NAT router 2 are connected to each other's external (global) “IP address: 3.3.3.3; 1.1.1.1”. As shown in FIG. 2, the same “source address: 192.168.0.1” and “source port number: 5000” are used to perform communication at “port number: 5000”. In addition, the PC 1 transmits a packet to “destination address: 3.3.3.3” and “destination port number: 5000”, and the PC 2 transmits “destination address: 1.1.1.1” and “destination port”. Even if a packet is transmitted to the number “5000” and the communication is attempted, the “source port number: 20000, 30000” converted by the NAT routers 1 and 2 is respectively the “destination port” of the NAT router 2 and 1. Number: because it does not coincide with the 5000 ", can not pass through the NAT router 2,1.

  In such a case, by using a technique generally known as “UDP hole punching”, it is possible to perform communication using the pattern 1 and the pattern 2. For example, when a server that is not under the control of a NAT router is prepared and each of the PCs 1 and 2 communicates with the server through the NAT routers 1 and 2, the server addresses after being converted by the NAT routers 1 and 2. Since PC1 can know the port number, the PC1 address and the converted port number are 33.3, 3.33.3, and the PC2 address is the PC1 address and the converted port number. The number is 20000 of 1.1.1.1 ”. If the NAT routers 1 and 2 are the routers of the pattern 1, the PCs 1 and 2 can pass through the NAT router by transmitting the addresses and port numbers of the counterpart PCs 2 and 1 notified from the server. Note that the addresses of PC1 and PC2 in FIG. 2 are both “192.168.0.1”, but these addresses may be the same or different because they are local addresses. . This also applies to the other drawings.

If the NAT routers 1 and 2 are pattern 2 routers, they cannot pass even if the port number notified from the server is used, but the source port number after conversion by NAT is often “30000”. Since it is a sequential change such as “→“ 30001 ”, it can be passed by successively testing the port numbers before and after the port number scan. In the above example, PC1 can pass “30000” if “30000” is useless, and PC2 can pass by trying “20001” if “20000” is useless. In other words, in the router of pattern 2, if it is for the same destination address, the source port number does not change even if the destination port number is changed as follows. You can expect to see combinations that pass through.
(PC1 side) Source port number after NAT conversion Destination port number
20001 → 30000
20001 → 30001 ◎
20001 → 30002
……
(PC2 side) Source port number after NAT conversion Destination port number
30001 → 20000
30001 → 20001 ◎
30001 → 20002
……

As described above, by using the UDP hole punching method, it is possible to perform communication using the NAT router of the pattern 1 as shown in FIG. 1A and the pattern 2 as shown in FIG. 1B. However, as shown in FIG. 1C, when both the NAT routers 1 and 2 are routers of pattern 3, that is, even if the same source address and source port number are transmitted to the same destination address, the destination port number only changes. In the case of NAT routers that perform different port conversions, the NAT routers cannot be supported. In other words, even if the previous and next port numbers are tried consecutively as in Pattern 2, the source port number after port conversion by the NAT router changes each time this is tried, so that I cannot catch up and cannot pass. If one of the NAT routers 1 and 2 is pattern 1 or pattern 2, the source port number after the return by the NAT router of pattern 1 or pattern 2 does not change, so by using the UD hole punching method, Communication can be performed.
(PC1 side) Source port number after NAT conversion Destination port number
20001 → 30000
20002 → 30001
20003 → 30002
20004 → 30003
……
(PC2 side) Source port number after NAT conversion Destination port number
30001 → 20000
30002 → 20001
30003 → 20002
30004 → 20003
……

  In view of such circumstances, the present invention provides a destination address when performing communication between two terminals under different NAT routers using a source address, a source port number, a destination address, and a destination port number. It is an object of the present invention to provide a communication system, a terminal device, and the like that can perform direct communication between both terminals even if a NAT router that performs conversion of different source port numbers only by changing the port number is interposed. In the description of each constituent element of the present invention below, the reference numerals of corresponding portions of the embodiment are shown in parentheses in order to facilitate understanding of the present invention. The present invention should not be construed as being limited to the configurations of the corresponding portions indicated by the reference numerals of the forms.

  The feature of the present invention is that a first terminal (TMa) under the first NAT router (NRa), a second terminal (TMb) under the second NAT router (NRb), and a server (not under the NAT router) In the communication system in which the first terminal and the second terminal communicate with each other via the first NAT router and the second NAT router using the source address, the source port number, the destination address and the destination port number. The server notifies the second terminal of the port number based on the transmission source port number used for data transmission to notify the transmission source port number by the first terminal, and sets the transmission source port number by the second terminal. The first terminal is notified of the port number based on the transmission source port number used for data transmission for notification (S5), and the first terminal notifies the second terminal. A first transmission means (C3) for transmitting data to the server to notify the source port number; a first port number receiving means (C4) for receiving a port number related to the second terminal notified from the server; Use a source port number different from the source port number used for data transmission by one transmission means, and transmit the data using the port number based on the port number received by the first port number reception means as the destination port number. And a first trial means (C5, C6) for trying to connect to the second terminal, and the second terminal transmits data to the server in order to notify the first terminal of the source port number. Used for data transmission by the transmission means (C3), the second port number reception means (C4) for receiving the port number related to the first terminal notified from the server, and the second transmission means Using a source port number different from the source port number and transmitting data using the port number based on the port number received by the second port number receiving means as the destination port number, and trying to connect to the second terminal. The second trial means (C5, C6) is provided.

  In this case, for example, the server further notifies the second terminal of the source address used for data transmission to notify the source port number by the first terminal, and the source port number by the second terminal. The first port number reception means of the first terminal further notifies the transmission source address of the second terminal notified from the server. The first trial means of the first terminal further attempts to connect to the second terminal using the source address received by the first port number reception means, and the second port number reception means of the second terminal Further receives the source address of the first terminal notified from the server, and the second trial means of the second terminal further uses the source address received by the second port number receiving means to use the first terminal. Attempting to connect to.

  Further, for example, the server notifies the second terminal of the port number obtained by adding “+1” to the transmission source port number used for data transmission in order to notify the transmission source port number by the first terminal, and Two terminals notify the first terminal of the port number obtained by adding “+1” to the transmission source port number used for data transmission to notify the transmission source port number, and the first trial means of the first terminal includes: The connection to the second terminal is attempted by transmitting data using the port number received by the first port number receiving means as the destination port number, and the second trial means of the second terminal is controlled by the second port number receiving means. A connection to the first terminal is attempted by transmitting data using the received port number as the destination port number. In addition, the server notifies the second terminal of the transmission source port number used for data transmission to notify the transmission source port number by the first terminal, and also notifies the transmission source port number by the second terminal. The source port number used for data transmission is notified to the first terminal, and the first trial means of the first terminal adds “+1” to the source port number received by the first port number receiving means. The second trial unit of the second terminal tries to connect to the second terminal by transmitting data with the port number as the destination port number, and the second trial unit of the second terminal adds “+1” to the transmission source port number received by the second port number receiving unit. The connection to the first terminal may be attempted by transmitting data using the port number to which "is added" as the destination port number.

  From another point of view, the present invention is characterized in that the first terminal (TMa) under the first NAT router (NRa) and the second terminal under the second NAT router (NRb) ( TMb) and a server (SV) not under the NAT router, the first terminal and the second terminal use the source address, source port number, destination address and destination port number to A terminal device constituting a first terminal in a communication system communicating with each other via a second NAT router, and transmitting means (C3) for transmitting data to a server in order to notify a source port number to the second terminal; The port number receiving means (C4) for receiving the port number related to the second terminal notified from the server is different from the source port number used for data transmission by the transmitting means. Trial means (C5, C6) that uses the source port number and tries to connect to the second terminal by transmitting data using the port number based on the port number received by the port number receiving means as the destination port number. There is also a terminal device.

  In the present invention configured as described above, prior to the direct communication between the first and second terminals, the first and second transmission means of the first and second terminals first send the source port to the other party, respectively. Send data to the server to notify the number. The server notifies the second and first terminals of the port number based on the transmission source port number used for data transmission by the first and second transmission means, respectively. In the first and second terminals, the first and second port number receiving means receive the port numbers notified from the server, respectively, and the first and second trial means are based on the first and second transmitting means. By using a transmission source port number different from the transmission source port number used for data transmission and transmitting the data with the port number based on the received port number as the destination port number, the data is transmitted to the second and first terminals. Try each connection. In this case, if the transmission source port number is changed, both NAT routers have a property of changing the transmission source port number according to a certain rule. Therefore, the first and second terminals that control the first and second terminals are used. Regardless of the type of 2NAT router, the client terminals A and B can communicate directly. Therefore, according to the present invention, no matter what type the first and second NAT routers dominate the first and second terminals, the process of determining the type of the first and second NAT routers is not required, The first and second terminals can communicate directly only by changing the transmission source port number used for transmission to the server.

  Furthermore, the embodiment of the present invention is not limited to the invention of the communication system and the terminal device, but is also implemented as an invention of a communication method applied to the communication system, a communication method applied to the terminal device, and an invention of a computer program. It is possible.

It is a figure for demonstrating an example of the end point independent mapping which is the pattern 1 of the behavior patterns of a NAT router. It is a figure for demonstrating an example of the address dependence mapping which is the pattern 2 of the behavior patterns of a NAT router. It is a figure for demonstrating an example of the address & port number dependence mapping which is the pattern 3 among the behavior patterns of a NAT router. It is a figure for demonstrating the problem in communication between the two terminals under the NAT router. 1 shows a configuration example of a network session system according to an embodiment of the present invention. A communication mode from the PCs 1 and 2 (clients A and B) to the server is shown. A communication mode from the server to PCs 1 and 2 (clients A and B) is shown. A communication mode between PC1 and PC2 (clients A and B) is shown. It is a flowchart which shows the example of a connection operation | movement of the client terminal by one Embodiment of this invention. It is a flowchart which shows the connection assistance operation example of the server by one Embodiment of this invention.

[Overview of system configuration]
FIG. 3 shows a configuration of a network session system according to an embodiment of the present invention. This network session system includes a session management server (also simply referred to as a server) SV, a plurality of NAT routers NR: NRa to NRd (the symbol “NR” representatively represents a NAT router), and subordinates of each NAT router NR. Each of the session terminals TM: TMa to TMd (symbol “TM” representatively represents a session terminal) is a communication system. The session management server SV, the plurality of NAT routers NR: NRa to NRd, and the session terminals TM: TMa to TMd are communicably connected via a wide area communication network CN such as the Internet.

  The session management server SV is not under the NAT but performs connection support between the session terminals TM as members, for example, a connection procedure between the session terminals TM performed before the start of the session. After connection is established between the session terminals TM, for example, between the session terminals TMa to TMd, the performance of audio data or the like is directly performed between the session terminals TMa to TMd under the NAT without using the session management server SV. Information is sent and received.

  The NAT router NR is provided with a plurality of host devices in addition to the illustrated session terminal TM, relays data between a local network constituted by these devices and the wide area communication network CN, and between the two networks. A NAT function for converting an address and a port number is provided. That is, the NAT router NR automatically converts between a local address and port number that are appropriately allocated and used only in each local network, and a global address and port number on the wide area communication network CN. Three types of NAT functions are known as described above with reference to FIGS. 1A to 1C.

  A plurality of session terminals TMa to TMd that are members of a network music session are also called client terminals or simply clients, and are electronic music apparatuses capable of playing musical instruments and / or karaoke, respectively. That is, each session terminal TM is a kind of computer having an electronic music information processing function, and an electronic music device such as a personal computer (PC) in which an electronic musical instrument or a music information processing application is installed can be used. . Further, there are cases where an electronic musical instrument is used as the session terminal TM and karaoke is not performed, and there is a case where only a karaoke is performed using a PC with a music information processing application as the session terminal TM. Although the number of session terminals TM (number of members) is four in FIG. 3, the number is not limited to this, and may be more or less than four.

[Procedure to obtain the converted address and port number]
A communication system according to an embodiment of the present invention includes a plurality of session terminals (hereinafter referred to as “client terminals” or simply “clients” or “terminals”) TMa to TMd under the control of different NAT routers NRa to NRd, Each client terminal TMa-TMd uses a source address, a source port number, a destination address, and a destination port number, and each NAT router uses a session management server (hereinafter simply referred to as “server”) SV. Direct communication is performed via NRa to NRd. However, as described with reference to FIG. 2, the NAT router NR to which a certain client terminal TM belongs changes pattern 3 (address & port number dependent mapping) in which a different source port number is converted only by changing the destination port number. ) Type (see FIG. 1C), it is necessary to establish communication (connection) between the terminals TMa to TMd. 4A to 4C show a procedure up to communication between two client terminals according to an embodiment of the present invention. In the following, a case where a connection is established between the client (A) TMa and the client terminal (B) TMb will be described as an example. In the following description, the client (A) TMa is described as PC1 and the client terminal (B) TMb is described as PC2.

  Prior to direct communication between the PCs 1 and 2, first, as shown in FIG. 4A, the PC 1 uses “source address: 192.168.0.1” and “source port number: 5000” to “ Destination address: 2.2.2.2 ”and“ destination port number: 5000 ”, that is, a packet (data) is transmitted to server SV. The PC 2 also uses the “source address: 192.168.0.1” and “source port number: 5000” to “destination address: 2.2.2.2” and “destination port number: 5000”, A packet is transmitted to the server SV. The server SV receives the packets from PC1 and PC2, and confirms “transmission source address: 1.1.1.1” and “transmission source port number: 30000”, which are the translation results by the NAT router under the control of PC1. In both cases, “transmission source address: 3.3.3.1” and “transmission source port number: 40000”, which are the conversion results by the NAT router under the control of PC2, are confirmed.

  Next, as shown in FIG. 4B, the server SV determines “source address: 1.1.1.1” regarding the confirmed PC 1 as the address of the PC 1 and “source port number: “Port number: 30001” obtained by adding “+1” to “30000” is estimated as the port number of PC1. Then, the server SV notifies the PC 2 that “the address of the PC 1 is“ 1.1.1.1 ”and the port number of the PC 1 is probably“ 30001 ””. Further, the server SV determines “source address: 3.3.3.3” relating to the confirmed PC 2 as the address of the PC 2 and adds “+1” to “source port number: 40000” relating to the confirmed PC 2. The estimated “port number: 40001” is estimated as the port number of PC2. Then, the server SV notifies the PC 1 that “the address of the PC 2 is“ 3.3.3.3 ”and the port number of the PC 1 is probably“ 40001 ””. PC1 and PC2 receive these notifications, respectively.

  Next, as shown in FIG. 4C, the PC 1 secures a “transmission source port number: 5001” different from the “transmission source port number: 5000” used when the packet is transmitted to the server described above. Then, the PC 1 uses the “source address: 192.168.0.1” and the secured “source port number: 5001” to notify the “destination address: 3.3.3.3” notified from the server. And “destination port number: 40001”, that is, the packet is transmitted to the PC 2. On the other hand, the PC 2 also secures a “source port number: 5001” different from the “source port number: 5000” used when the packet is transmitted to the server described above. Then, the PC 2 uses the “source address: 192.168.0.1” and the secured “source port number: 5001” to notify the “destination address: 1.1.1.1” notified from the server. And “destination port number: 30001”, that is, the packet is transmitted to PC1. In the above example, the transmission source port number is changed by adding “+1” to the transmission source port number used last time. However, if the transmission source port number is different from the previous transmission source port number, another transmission source port number is used. May be.

  In this case, if the NAT router under the control of PC1 and PC2 uses a source port number different from the source port number used last time, the source port converted last time is used regardless of the patterns 1 to 3 described above. Has the property of changing the number. This change in the source port number is normally converted sequentially (that is, “+1” is added to the previous conversion result). Therefore, the port numbers of PC1 and PC2 match, and PC1 and PC2 can communicate with each other.

[Operation example]
Next, a specific operation example will be described. FIG. 5 shows a connection operation example of the client terminal TM according to one embodiment of the present invention, and FIG. 6 shows a connection assistance operation example of the server SV according to one embodiment of the present invention. In other words, FIG. 5 shows a flowchart of the computer program according to the connection operation example executed by the CPU of the client terminal TM. FIG. 6 shows a flowchart of a computer program according to a connection assistance operation example executed by the CPU of the server SV.

  First, when there is an instruction to start connection by a user operation, the client terminal TM (CPU as the control unit) starts executing the program shown in FIG. 5 and performs connection to the server SV in step C1. Notice. Next, the client terminal TM determines whether or not a connection start instruction has been received from the server SV in Step C2, that is, whether or not another participant has appeared. If the connection start instruction has not arrived from the server SV, the client terminal TM determines “No” in Step C2, and repeats the process of Step C2 to wait for the arrival of the connection start instruction. In the above description, the connection notification of one client terminal TM to the server SV has been described. In this state, the other client terminals TM communicating with each other are also performing the processes of steps C1 and C2. Also in the subsequent operation of the client terminal TM, the plurality of client terminals TM communicating with each other execute the program processing shown in FIG.

  On the other hand, the server SV starts execution of the program shown in FIG. 6, and determines in step S1 whether or not a notification of connection has arrived from the client terminal TM by the processing in step C1. In a state where the connection notification has not arrived, the server SV determines “No” in step S1, and waits for a connection notification from the client terminal TM. When a connection notification is received from one client terminal TM, the server SV determines “Yes” in step S1, and proceeds to step S2. The server SV determines whether there are two or more client terminals TM waiting for connection in step S2 (whether other participants have appeared). If there are not two or more client terminals TM waiting for connection, the server SV determines “No” in step S2, returns to the step S1, and again notifies the connection from the other client terminals TM. wait. Then, the processes in steps S1 and S2 are repeated. In this case, when the notification of connection from the two client terminals TM arrives, “Yes” is determined in step S2. However, since there may be more than two client terminals TM, the server SV waits for some time before determining “Yes” in step S2 from the notification of connection from one client terminal TM. It is good to make it. During this waiting time, the server SV continues to determine “No” in step S2 and repeats the processes in steps S1 and S2.

  If there are two or more client terminals TM waiting for connection and it is determined “Yes” in step S2, the server SV connects to all client terminals TM waiting for connection in step S3. Send start instructions. After the processing in step S3, the server SV determines in step S4 whether or not packets for the port number P1 have been received from all client terminals TM instructed to start connection. In a state where packets from all client terminals TM to the port number P1 are not received, the server SV determines “No” in step S4 and waits for reception of the packets.

  On the other hand, each client terminal TM waiting for a connection start instruction receives a connection start instruction in step C2 and receives a “Yes” when a connection start instruction is transmitted from the server SV while waiting in step C2. And proceed to Step C3. In step C3, each client terminal TM transmits a packet to the port number P1 to the server SV using a predetermined transmission source address and transmission source port number. After the process of step C3, each client terminal TM determines whether a notification of the port number and address of the connection destination has arrived from the server SV in step C4. Each client terminal TM continues to make a “No” determination in step C4 and waits for a notification of the connection destination port number and address until notification of the connection destination port number and address arrives.

  The server SV waiting for reception of the packet receives the transmitted packet every time a packet is transmitted from the client terminal TM in step S4. When the server SV receives packets from all the client terminals TM notified of connection to the port number P1, the server SV determines “Yes” in step S4, and proceeds to step S5. In step S5, the server SV transmits a notification of the other party's connection destination address and the estimated port number to all the client terminals TM. Specifically, the server SV obtains an estimated port number by adding “+1” to the transmission source port number of the packet received from each client terminal TM, and the transmission source address and the estimated port number of the received packet. Is transmitted to all the client terminals TM.

  Next, in step S6, the server SV determines whether any of the “connection complete”, “connection retry notification”, and “connection failure” packets has arrived from the client terminal TM. If the packet has not arrived, the server SV determines “No” in step S6 and waits for the packet to arrive. Regarding “connection completion” in the determination in step S6, it is determined whether or not there has been a notification from all the client terminals TM that transmitted a connection start instruction in the process in step S5, whereas “connection retry notification”. As for “connection failure”, it is determined whether there is a notification from any one of the client terminals TM.

  On the other hand, each client terminal TM waiting for notification of the connection destination port number and address receives the connection destination address and the estimated port number in step C4 when the connection destination address and the estimated port number are received from the server SV. And it determines with "Yes" and progresses to step C5. In step C5, the client terminal TM sets a new source port number that is different from the source port number used when the packet is transmitted to the server SV in step C3. In this case, a new source port number is set by adding “+1” to the source port number used when the packet is transmitted to the server SV. However, this is used when the packet is transmitted to the server SV. If it is different from the source port number, another source port number may be set.

  Next, in step C6, the client terminal TM uses the same predetermined source address and the newly set source port number as in step C3, and estimates the partner client terminal TM notified from the server SV. A connection with the partner client terminal TM is attempted by transmitting a trial packet (trial data) to the port number and address.

  As described above, the client terminal TM is not notified of the connection with the partner client terminal TM using only the estimated port number and address of the partner client terminal TM notified from the server SV. The connection may be attempted using a plurality of port numbers before and after the estimated port number and the notified address. The port numbers before and after are, for example, “+1” from several port numbers obtained by adding “+1”, “+2”, “+3”... To the notified estimated port number and the notified estimated port number. , “+2”, “+3”,... This is due to the following reason. Even if the NAT router that controls the partner client terminal TM is one of the patterns 1 to 3 described above, if a port of the NAT router that controls the partner client terminal TM happens to be used, The NAT router NR is not in use and may be changed to a port before and after the estimated port number notified from the server SV. Therefore, in this case, the trial packet may not reach the partner client terminal TM in the trial of the notified estimated port number.

  After the processing in step C6, each client terminal TM determines whether or not a trial packet from the partner client terminal TM to be connected has arrived in step C7. In a state where the trial packet from the partner client terminal TM has not arrived, each client terminal TM determines “No” in Step C7 and proceeds to Step C8. In step C8, the client terminal TM determines whether or not the maximum time for waiting for a packet from the partner client terminal TM has elapsed. While the maximum time has not elapsed, the client terminal TM makes a “No” determination at step C8 and returns to step C7 until the trial packet from the partner client terminal TM arrives or the maximum time The processes in steps C7 and C8 are repeatedly executed until the time has elapsed.

  When a trial packet arrives during the cyclic processing in steps C7 and C8, each client terminal TM determines “Yes” in step C7 and proceeds to step C9. In step C9, each client terminal TM notifies the server SV that the connection has been completed. As a result, the client terminal TM that has received the trial packet from the partner client terminal TM establishes a direct connection with the partner client terminal TM and ends this connection operation. Since the received trial packet includes a transmission source address and a transmission source port number relating to the partner client terminal TM, the client terminal TM that has received the trial packet can recognize the address and port number of the partner client terminal TM. Thereafter, the client terminal TM shifts to a music session operation (ensemble) with the partner client terminal TM.

  On the other hand, when the maximum time has elapsed in a state where the trial packet from the partner client terminal TM has not arrived, each client terminal TM determines “Yes” in Step C8 and proceeds to Step C10. In step C10, each client terminal TM determines whether or not the maximum number of trials for packet transmission by the process of step C6 has been performed. When the maximum number of trials has not been performed, the client terminal TM determines “No” in Step C10 and proceeds to Step C11. In step C11, each client terminal TM notifies the server SV of a connection retry, returns to step C3, and repeatedly executes the connection retry including steps C3 to C8, C10, and C11 described above. When the maximum number of attempts for packet transmission is performed, each client terminal TM determines “Yes” in step C10, notifies the server SV that the connection has failed in step C12, and gives up the connection. Then, this connection operation is terminated. In this case, each client terminal TM cannot connect to the partner client terminal TM.

  On the other hand, when the server SV that is repeatedly performing the process in step S6 receives from the client terminal TM one of the “connection complete”, “connection retry notification”, and “connection failure” packets, “Yes” in step S6. ”And proceed to step S7. In step S7, the server SV executes a branch process in response to “connection complete”, “connection retry notification”, or “connection failure” received from the client terminal TM.

  In this case, when receiving a “connection complete” packet, the server SV proceeds to step S8, completes the connection, and deletes the client terminal TM that has received the packet from the client terminal TM waiting for connection. When the “connection retry notification” packet is received, the server SV returns to step S3 and repeats the processes of steps S3 to S7 described above. Further, when the “connection failure” packet is received, the server SV proceeds to step S9, determines that the connection has failed, and deletes the client terminal TM that has received the packet from the client terminal TM waiting for connection. Then, after the processing of steps S8 and S9, the original standby state is restored.

  As described above, in the above-described embodiment, prior to direct communication between both client terminals A and B, first, a packet is transmitted from the client terminals A and B to the server SV, and the server SV is used for transmission. The port number obtained by adding “+1” to the transmission source port number is determined as the estimated port number, and the other party's transmission source address and estimated transmission source port number are notified to the client terminals A and B. After that, if the client terminals A and B change the transmission source port number different from the transmission source port number used at the time of transmission to the server SV, the client terminal A and B will use the other party's port number and the estimated port number notified from the server SV. Can communicate directly with each other. In other words, in the above embodiment, the NAT routers A and B control the client terminals A and B by using the property that when the source port number is changed, the NAT routers A and B change the source port number sequentially. Regardless of the types of A and B, the client terminals A and B can communicate directly. Therefore, according to the above embodiment, no matter what type of NAT routers A and B dominate the client terminals A and B, it is not necessary to determine the type of NAT routers A and B. A and B can communicate directly only by changing the transmission source port number used for transmission to the server SV.

[Modification]
In the above embodiment, in step S5 of FIG. 4B and FIG. 6, the server SV adds “+1” to the transmission source port number of the client terminal TM transmitted from the client terminal TM and converted by the NAT router NR. Thus, the estimated port number is transmitted to the other client terminal TM. However, the server SV may transmit the source port number itself of the client terminal TM transmitted from the client terminal TM and converted by the NAT router NR to the client terminal TM of the other party. In this case, the partner client terminal TM may use a port number obtained by adding “+1” to the source port number itself transmitted from the server SV as the destination port number. Further, the server SV does not give the estimated port number obtained by adding “+1” to the transmission source port number and the transmission source port number itself, but the estimated port number converted using a predetermined rule to the client terminal TM. The client terminal TM may notify the port number obtained by converting the estimated port number notified in accordance with the rule as the destination port number.

  In the above embodiment, the server SV determines the port number obtained by adding “+1” to the source port number converted and used by the NAT router NR when sending the packet as the estimated port number, and determines the partner client. The terminal TM was notified. However, instead of this, the server SV increases or decreases the estimated port number (for example, “+2”, “+”), which is a value other than “+1”, according to the behavior of the NAT router NR (transmission source number conversion mode). +3 "... or" -2 "," -3 "..., etc.) may be determined. The port number obtained by adding the determined increase / decrease value to the transmission source port number sent from the client terminal TM or the port number obtained by subtracting the determined increase / decrease value from the transmission source port number is determined as the estimated port number. The partner client terminal TM may be notified. This is because a certain NAT router may not convert the source port number sequentially.

  Furthermore, in the above embodiment, in step S5 of FIG. 4B and FIG. 6, the server SV notifies all the client terminals TM of the connection destination address and the estimated port number of the connection destination at the same time. However, the server SV may notify both client terminals TM of the connection destination address separately from the estimated port number. If all the client terminals TM recognize the connection destination addresses in advance, in step S5 in FIG. 4B and FIG. 6, the server SV assigns only the estimated port number of the connection destination to all the client terminals. You may make it notify TM.

NR: NRa to NRd ... NAT router, TM: TMa to TMd ... session terminal (client terminal), SV ... session management server, CN ... wide area communication network

Claims (8)

A first terminal under the first NAT router, a second terminal under the second NAT router, and a server not under the NAT router, wherein the first terminal and the second terminal have a source address, In a communication system that communicates with each other via the first NAT router and the second NAT router using a source port number, a destination address, and a destination port number,
The server notifies the second terminal of a port number based on a transmission source port number used for data transmission to notify the transmission source port number by the first terminal, and transmits the transmission source by the second terminal. Notifying the first terminal of a port number based on a source port number used for data transmission to notify the port number;
The first terminal is
First transmitting means for transmitting data to the server to notify the second terminal of a source port number;
First port number receiving means for receiving a port number related to the second terminal notified from the server;
A transmission source port number different from the transmission source port number used for data transmission by the first transmission means is used, and the port number based on the port number received by the first port number reception means is used as a destination port number. First trial means for trying to connect to the second terminal by transmitting, and the second terminal,
Second transmission means for transmitting data to the server to notify the first terminal of a source port number;
Second port number receiving means for receiving a port number related to the first terminal notified from the server;
A transmission source port number different from the transmission source port number used for data transmission by the second transmission means is used, and the port number based on the port number received by the second port number reception means is used as a destination port number. A communication system comprising: second trial means for trying to connect to the second terminal by transmitting. The communication system according to claim 1,
The server further notifies the second terminal of a source address used for data transmission to notify the source port number by the first terminal, and sets the source port number by the second terminal. Notifying the first terminal of the source address used to transmit the data for notification,
The first port number receiving means of the first terminal further receives the source address of the second terminal notified from the server;
The first trial means of the first terminal further attempts to connect to the second terminal using the source address received by the first port number receiving means,
The second port number receiving means of the second terminal further receives the source address of the first terminal notified from the server;
The communication system in which the second trial unit of the second terminal further attempts to connect to the first terminal using the source address received by the second port number reception unit. The communication system according to claim 1 or 2,
The server notifies the second terminal of a port number obtained by adding “+1” to the transmission source port number used for data transmission to notify the transmission source port number by the first terminal. 2 notifies the first terminal of the port number obtained by adding “+1” to the source port number used for data transmission to notify the source port number by the two terminals;
The first trial unit of the first terminal tries to connect to the second terminal by transmitting data using the port number received by the first port number receiving unit as a destination port number, and the second terminal The second trial means attempts to connect to the first terminal by transmitting data using the port number received by the second port number receiving means as the destination port number. The communication system according to claim 1 or 2,
The server notifies the second terminal of the source port number used for data transmission to notify the source port number by the first terminal, and notifies the source port number by the second terminal. To notify the first terminal of the source port number used to transmit the data,
The first trial unit of the first terminal transmits data to the second terminal by transmitting data using a port number obtained by adding “+1” to the source port number received by the first port number receiving unit as a destination port number. And the second trial unit of the second terminal transmits data using the port number obtained by adding “+1” to the source port number received by the second port number receiving unit as the destination port number. A communication system that attempts to connect to the first terminal. A first terminal under the first NAT router, a second terminal under the second NAT router, and a server not under the NAT router, wherein the first terminal and the second terminal have a source address, In a communication method of communicating with each other via the first NAT router and the second NAT router using a source port number, a destination address, and a destination port number,
The server notifies the second terminal of a port number based on a transmission source port number used for data transmission to notify the transmission source port number by the first terminal, and transmits the transmission source by the second terminal. Notifying the first terminal of a port number based on a source port number used for data transmission to notify the port number;
The first terminal is
Sending data to the server to notify the second terminal of the source port number;
Receiving the port number regarding the two terminals notified from the server;
By using a transmission source port number different from the transmission source port number used for transmission of data to the server, and transmitting the data with the port number based on the received port number related to the second terminal as the destination port number, Trying to connect to a second terminal, and the second terminal
Sending data to the server to notify the first terminal of the source port number;
Receiving the port number related to the one terminal notified from the server;
By using a transmission source port number different from the transmission source port number used for transmitting data to the server, and transmitting the data with the port number based on the received port number relating to the first terminal as the destination port number, A communication method characterized by trying to connect to a second terminal. A first terminal under the first NAT router, a second terminal under the second NAT router, and a server not under the NAT router, wherein the first terminal and the second terminal have a source address, A terminal device constituting the first terminal in a communication system that communicates with each other via the first NAT router and the second NAT router using a source port number, a destination address, and a destination port number,
Transmitting means for transmitting data to the server to notify the second terminal of the source port number;
Port number receiving means for receiving a port number related to the second terminal notified from the server;
By using a transmission source port number different from the transmission source port number used for data transmission by the transmission means, and transmitting data using the port number based on the port number received by the port number reception means as the destination port number A terminal device comprising trial means for trying to connect to the second terminal. A first terminal under the first NAT router, a second terminal under the second NAT router, and a server not under the NAT router, wherein the first terminal and the second terminal have a source address, A communication method of a terminal device constituting the first terminal in a communication system that communicates with each other via the first NAT router and the second NAT router using a source port number, a destination address, and a destination port number,
Sending data to the server to notify the second terminal of the source port number;
Based on the received port number using a source port number that is different from the source port number used to transmit data to the server and that receives the port number related to the second terminal notified from the server A communication method for a terminal device, characterized in that a connection to the second terminal is attempted by transmitting data using a port number as a destination port number. A first terminal under the first NAT router, a second terminal under the second NAT router, and a server not under the NAT router, wherein the first terminal and the second terminal have a source address, A computer program applied to a terminal device constituting the first terminal in a communication system that communicates with each other via the first NAT router and the second NAT router using a source port number, a destination address, and a destination port number. And
A transmission step of transmitting data to the server to notify the second terminal of the transmission source port number;
A port number receiving step of receiving a port number related to the second terminal notified from the server;
By using a transmission source port number different from the transmission source port number used for data transmission in the transmission step, and transmitting data using the port number based on the port number received in the port number reception step as a destination port number A computer program applied to a terminal device, comprising: a trial step of trying to connect to the second terminal.

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