JP6331421B2 - Communication system and server - Google Patents

Description

  The present invention relates to a communication system and a server for performing 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. Here, the behavior patterns of these three NAT routers will be described. 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 ". Note that when the source port number is changed by the NAT router in the present invention, the transmission source port number change ("+1" in the above example) that is sequentially changed as in patterns 2 and 3 is changed. Corresponds to the changed source port number.

  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 PC1 and PC2 communicate with this server through the NAT routers 1 and 2, the server receives the address after conversion by the NAT routers 1 and 2, and Since the port number can be known, PC1 says “PC2 address and converted port number is 33.3, 30000,” and PC2 says “PC1 address and converted port number. Is the number 20000 of 1.1.1.1 ”. If the NAT routers 1 and 2 are the routers of pattern 1, PC1 and PC2 can pass through the NAT router by transmitting the addresses and port numbers of the counterpart PC2 and PC1 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 conversion by the NAT router of pattern 1 or pattern 2 does not change, so by using the UDP 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 server, and the like that can perform direct communication between both terminals even if a NAT router that converts different source port numbers is present only by changing the port number. 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) SV), in which the first terminal and the second terminal communicate with each other via the first NAT router and the second NAT router, the first terminal notifies the second terminal via the server of the source port number. In order to do so, a first transmission means (C3) for transmitting data to the server via the first NAT router is provided, and the second terminal transmits the source port number to the first terminal via the server. A second transmission means (C3) for transmitting data to the server via the 2NAT router, wherein the server receives the data transmitted to the server by the first transmission means and the second transmission means, respectively; A first estimated port number related to the first terminal is estimated from the data receiving means (S4) and the source port number used for data transmission by the first transmitting means received by the data receiving means, and the estimated first The first guess port number is notified to the second terminal via the second NAT router, and the second guess for the second terminal is determined from the source port number used for data transmission by the second sending means received by the data receiving means. Port number estimating means (S5) for estimating the port number and notifying the estimated second estimated port number to the first terminal via the first NAT router, the first terminal further comprising port number estimating means The first port number receiving means (C4) for receiving the second guessed port number notified by, and the data sent to the server by the first transmitting means A second trial port number based on the second estimated port number received by the first port number receiving means, using the same source port number as the source port number, and for transmitting data to the server by the second transmitting means The source port number used is a first NAT router and a second NAT router, with a second trial port number that is different from the source port number when the source port number is changed by the NAT router as a destination port number. After attempting to connect to the second terminal by transmitting data to the second terminal via the network , and after attempting to connect to the second terminal using the second trial port number as the destination port number, the first transmission is further performed. The second estimated port received by the first port number receiving means using the same source port number as the source port number used for transmitting data to the server by the means A first trial router number and a second NAT port, with a fourth trial port number based on the number and a fourth trial port number equal to the transmission source port number used for data transmission to the server by the second transmission means. First trial means (C5) for trying to connect to the second terminal by transmitting data to the second terminal via the router, and the second terminal is further notified by the port number estimating means. The second port number using the same source port number as the source port number used for transmitting the data to the server by the second port number receiving means (C4) for receiving the 1 guess port number and the second sending means What is the first trial port number based on the first estimated port number received by the receiving means, and is the source port number used for transmitting data to the server by the first transmitting means? Data is transmitted to the first terminal via the second NAT router and the first NAT router, with the first trial port number that is different by the change of the source port number when the source port number is changed by the NAT router as the destination port number. Then, after attempting to connect to the first terminal and attempting to connect to the first terminal with the first trial port number as the destination port number, the second transmission means is further used for data transmission to the server. A third trial port number based on the first guess port number received by the second port number receiving means, using the same source port number as the transmitted source port number, and The first trial port number equal to the source port number used for transmission is set as the destination port number, and the first NAT port is sent through the second NAT router and the first NAT router. In that a second attempt means for attempting to connect to the first terminal by transmitting (C5) the data at the end.

In this case, for example, the first estimated port number is the source port number used for transmitting data to the server by the first transmitting means, and the source port when the source port number is changed by the NAT router The second estimated port number is different from the source port number used for transmitting data to the server by the second transmission means, and the source port number is changed by the NAT router. The port number is different by the change of the source port number when
Further, when the transmission source port number is changed by the NAT router, the change of the transmission source port number is “+1”, and the first estimated port number is used for transmission of data to the server by the first transmission means. The second estimated port number is “+1” larger than the transmission source port number used for transmitting data to the server by the second transmission means. Is the only large port number

  In the present invention configured as described above, the first trial means uses the same source port number as the source port number used for data transmission to the server by the first transmission means, and uses the second trial port number. That is, the second trial port differs from the transmission source port number used for transmission of data to the server by the second transmission means by the change of the transmission source port number when the transmission source port number is changed by the NAT router. A first NAT router and a second NAT router with a number (for example, a second trial port number larger by “+1” than the source port number used for transmission of data to the server by the second transmission means) as the destination port number. The connection to the second terminal is attempted by transmitting data to the second terminal via the terminal. On the other hand, the second trial means uses the same source port number as the source port number used for data transmission to the server by the second transmission means, and uses the first trial port number, that is, the server by the first transmission means. The first trial port number that differs from the transmission source port number used for data transmission by the amount of change (for example, “+1 more than the transmission source port number used for data transmission to the server by the first transmission means”). The first trial port number (which is larger by “) is used as the destination port number, and data is transmitted to the first terminal via the second NAT router and the first NAT router, thereby attempting to connect to the first terminal. In this case, since the destination address in the data transmission by the first trial means and the second trial means is different from the destination address in the data transmission to the server by the first transmission means and the second transmission means, the first terminal and the second The transmission source port number in the two terminals differs from the transmission source port number at the time of data transmission by the first transmission unit and the second transmission unit by the change amount (for example, “ +1 ”increases each). Therefore, if the first NAT router and the second NAT are the routers of the pattern 2 or the pattern 3 described above, a mutually communicable connection is established between the first terminal and the second terminal via the first NAT router and the second NAT. .

However, if the first NAT router or the second NAT router is the pattern 1 described above, a connection capable of mutual communication between the first terminal and the second terminal via the first NAT router and the second NAT router is not established. However, in this case, if the transmission source port numbers related to the first terminal and the second terminal in the trial are not changed, the transmission source port number is not changed by the first NAT router or the second NAT router which is pattern 1 . In the present invention configured as described above, the first trial means further includes the fourth trial port number, that is, the second transmission means to the server in addition to the trial using the second trial port number as the destination port number. An attempt is made to use a port number equal to the source port number used for data transmission as the destination port number. On the other hand, in addition to the trial using the first trial port number as the destination port number, the second trial means uses the third trial port number, that is, the transmission source port number used for transmitting data to the server by the first transmission means. Attempts to make the destination port number equal to In this case, as described above, if the transmission source port numbers related to the first terminal and the second terminal in the trial are not changed, the transmission source port number is not changed by the first NAT router or the second NAT which is pattern 1. Therefore, even if the first NAT router or the second NAT router is a pattern 1 router, a connection capable of mutual communication is established between the first terminal and the second terminal via the first NAT router and the second NAT. As a result, according to the present invention, it is necessary to determine the type of the first NAT router and the second NAT router regardless of the type of the first NAT router and the second NAT router that dominate the first and second terminals. Instead, the first and second terminals can easily communicate directly with each other.

  Further, when the present invention is viewed from another point of view, the feature of the present invention is that the first terminal (TMa) subordinate to the first NAT router (NRa) and the second terminal subordinate to the second NAT router (NRb) ( TMb) and a server (SV) not under the control of the NAT router, wherein the first terminal and the second terminal communicate with each other via the first NAT router and the second NAT router, and the first terminal and the second terminal Before the two terminals communicate with each other, the first terminal transmits data to the server to notify the second terminal via the server of the transmission source port number (C3), and the second terminal notified from the server (C4), and using the same source port number as the source port number used for data transmission to the server, the second estimated port number notified from the server Data is transmitted to the second terminal through the first NAT router and the second NAT router using the new second trial port number as the destination port number, and thereafter, at least the received second guess port number and source port number are A fourth trial port number equal to the source port number used for transmitting data to the server by the second terminal is derived using the change in the source port number when changed by the NAT router; Attempting to connect to the second terminal by transmitting data to the second terminal via the first NAT router and the second NAT router using the derived fourth trial port number as the destination port number (C5), and the second terminal Transmits the data to the server to notify the transmission source port number to the first terminal via the server (C3) and is notified from the server. The first estimated port number received from the server using the same source port number as the source port number used for transmitting data to the server (C4). Is transmitted to the first terminal through the second NAT router and the first NAT router with the first trial port number equal to the destination port number as the destination port number, and then at least the received first guess port number and source port number A third trial port number equal to the source port number used for transmitting data to the server by the first terminal, using the change in the source port number when is changed by the NAT router; Data is transmitted to the first terminal through the second NAT router and the first NAT router using the derived third trial port number as the destination port number. (C5) is a server in a communication system that attempts to connect to the first terminal, and receives data transmitted from the first terminal to the server and receives data transmitted from the second terminal to the server. The receiving means (S4) and the transmission source port numbers of the first terminal and the second terminal used for transmitting the data received by the data receiving means are respectively those when the transmission source port number is changed by the NAT router. A port number that differs by the change in the source port number is estimated as the first estimated port number and the second estimated port number, the first estimated port number is notified to the second terminal, and the second estimated port number is set to the first estimated port number. A port number estimation means (S5) for notifying one terminal.

  In the other feature of the present invention, as described above, the first terminal and the second terminal are the second NAT router and the first NAT router and the second NAT router are the routers of any one of the patterns 1 to 3. It becomes possible to directly communicate with each other via the first NAT router. Also in this case, if the first terminal and the second terminal have the function of sequentially changing the destination port number (for example, a function based on the UDP hole punching method), the processing functions on the first terminal and the second terminal side Without changing the server, only the function on the server side is changed, and a connection capable of mutual communication is established between the first terminal and the second terminal via the first NAT router and the second NAT router. As a result, according to another feature of the present invention, it is not necessary to change the functions of many terminals, and the communication system is easily improved.

  Furthermore, the implementation of the present invention is not limited to the invention of the communication system and the server, but can also be implemented as an invention of a communication method applied to the communication system, a method applied to the server, and an invention of a computer program. It is.

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 PC 1 and PC 2 (clients A and B) to the server is shown. A communication mode from the server to PC1 and PC2 (clients A and B) is shown. An example of connection between PC1 and PC2 (clients A and B) via the NAT routers of patterns 2 and 3 will be described. An example of inability to connect between PC1 and PC2 (clients A and B) via the pattern 1 NAT router will be described. An example of connection between PC1 and PC2 (clients A and B) via the pattern 1 NAT router 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 plurality of 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 the 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 4E show a procedure and an operation example 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 PC1 and PC2, first, as shown in FIG. 4A, PC1 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: 3.3.3.3” and “transmission source port number: 40000”, which are the conversion results by the NAT router under the control of PC 2, 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 2 is probably“ 40001 ””. PC1 and PC2 receive these notifications, respectively.

  Next, the connection operation between PC1 and PC2 will be described with reference to FIGS. 4C to 4E. FIG. 4C is a pattern 2 type router in which both NAT routers controlling PC1 and PC2 are defined as “address dependent mapping” or a pattern 3 type router defined as “address & port number dependent mapping”. A connection example between PC1 and PC2 (clients A and B) in a certain case is shown. FIG. 4D shows an example in which connection between PC1 and PC2 is impossible when both NAT routers are routers of the type of pattern 1 defined as “endpoint independent mapping”. FIG. 4E shows an example of connection between PC1 and PC2 when both NAT routers are routers of the pattern 1 type.

  In the present embodiment, PC1 and PC2 execute the following first connection trial and second connection trial in this order, respectively. In the first connection attempt, PC1 and PC2 are notified from the server using the same source address and source port number as the source address and source port number used when sending the packet to the server described above. Packets are transmitted to destination addresses and destination port numbers related to PC2 and PC1, respectively. In the second connection attempt, PC1 and PC2 are notified from the server by using the same source address and source port number as the source address and source port number used when sending the packet to the server described above. The packet is transmitted to the destination port number obtained by subtracting “+1” from the destination address related to PC2 and PC1 and the destination port number related to PC2 and PC1 notified from the server.

  First, the first connection trial will be specifically described. In this case, as shown in FIG. 4C, the PC 1 uses the same “source address: 192.168.0.1” and “source port number: 5000” as when the packet was transmitted to the server described above, A packet is transmitted to “destination address: 3.3.3.3” and “destination port number: 40001” notified from the server, that is, to the PC 2. On the other hand, the PC 2 uses the same “source address: 192.168.0.1” and “source port number: 5000” as those used when the packet is transmitted to the server described above. : 1.1.1.1 ”and“ destination port number: 30001 ”, that is, the packet is transmitted to the PC 1.

  First, a case will be described in which both NAT routers under the control of PC1 and PC2 are pattern 2 or pattern 3 type routers. In this case, since the destination address is different from the destination address when the packet is transmitted to the server described above, the source port number converted this time is the source port number converted last time (when the packet is transmitted to the server). The converted “transmission source port number: 30000, 40000”) is sequentially changed (“+1” is added to the previous conversion result). That is, in this first connection attempt, the source port number related to PC1 is converted to “30001”, and the source port number related to PC2 is converted to “40001”. Note that the source addresses related to PC1 and PC2 converted by both NAT routers are not changed. Therefore, “destination port number: 40001” in transmission of a packet from PC1 to PC2 matches “source port number: 40001” in transmission of a packet from PC2 to PC1. Further, “destination port number: 30001” in transmission of a packet from PC2 to PC1 matches “source port number: 30001” in transmission of a packet from PC1 to PC2. As a result, a communicable connection is established between PC1 and PC2 via both NAT routers.

  Next, the case where both NAT routers under the control of PC1 and PC2 are both pattern 1 type routers will be described. In this case, even if the destination address is different from the destination address when the packet is transmitted to the server described above, or the destination port number is different from the destination port number when the packet is transmitted to the server described above, As shown in FIG. 4D, the transmission source port number converted this time is the same as the transmission source port number converted last time (“transmission source port number: 30000, 40000” converted when the packet is transmitted to the server). It is. That is, in this first connection attempt, the source port number related to PC1 is converted to “30000”, and the source port number related to PC2 is converted to “40000”. In this case as well, the source addresses related to PC1 and PC2 converted by both NAT routers are not changed. Therefore, “destination port number: 40001” in transmission of a packet from PC1 to PC2 does not match “source port number: 40000” in transmission of a packet from PC2 to PC1. Further, “destination port number: 30001” in transmission of a packet from PC2 to PC1 does not match “source port number: 30000” in transmission of a packet from PC1 to PC2. As a result, a communicable connection between PC1 and PC2 via both NAT routers is not established.

  A case will be described in which the NAT router under the control of PC1 is a pattern 1 type router, and the NAT router under the control of PC2 is a pattern 2 or pattern 3 type router. In this case, since the transmission source port number related to PC2 is converted to “40001”, “destination port number: 40001” in the transmission of the packet from PC1 to PC2 is the packet from PC2 to PC1. Matches the “transmission source port number: 40001”. However, since the transmission source port number related to PC1 is converted to “30000”, “destination port number: 30001” in the transmission of the packet from PC2 to PC1 is the same as the case described above. It does not match the “source port number: 30000” in transmission. As a result, a communicable connection between PC1 and PC2 via both NAT routers is not established.

  Further, a case will be described where the NAT router under the control of PC1 is a pattern 2 or pattern 3 type router, and the NAT router under the control of PC2 is a pattern 1 type router. In this case, since the transmission source port number related to PC1 is converted to “30001”, “destination port number: 30001” in the transmission of the packet from PC2 to PC1 is the packet from PC1 to PC2, as in the case described above. Matches the “transmission source port number: 30001”. However, since the transmission source port number related to PC2 is converted to “40000”, “destination port number: 40001” in the transmission of the packet from PC1 to PC2 is the same as that in the above case. It does not match the “transmission source port number: 40000” in transmission. As a result, a communicable connection between PC1 and PC2 via both NAT routers is not established.

  Next, the second connection attempt for solving the state where the connection between the PC1 and PC2 is not established can be specifically described. In this case, as shown in FIG. 4E, the PC 1 uses the same “source address: 192.168.0.1” and “source port number: 5000” as when the packet was transmitted to the server described above, For “destination address: 3.3.3.3” notified from the server and “destination port number: 40000” obtained by subtracting “+1” from “destination port number: 40001” notified from the server, that is, PC2 Send a packet to On the other hand, the PC 2 uses the same “source address: 192.168.0.1” and “source port number: 5000” as those used when the packet is transmitted to the server described above. : 1.1.1.1 ”and“ destination port number: 30001 ”obtained by subtracting“ +1 ”from“ destination port number: 30001 ”notified from the server, that is, the packet is transmitted to PC1.

  First, a case will be described in which both NAT routers under the control of PC1 and PC2 are pattern 1 type routers. In this case, as shown in FIG. 4E, the destination port number in both transmissions between PC1 and PC2 is different from the destination port number when the packet was transmitted in the first connection attempt, but regarding both PC1 and PC2, The source port number converted this time is the same as the source port number converted in the first connection attempt. That is, even in this second connection attempt, the transmission source port number related to PC1 is converted to “30000”, and the transmission source port number related to PC2 is converted to “40000”. In this case as well, the source addresses related to PC1 and PC2 converted by both NAT routers are not changed. Therefore, “destination port number: 40000” in transmission of a packet from PC1 to PC2 matches “source port number: 40000” in transmission of a packet from PC2 to PC1. Further, “destination port number: 30000” in packet transmission from PC2 to PC1 matches “source port number: 30000” in packet transmission from PC1 to PC2. As a result, a communicable connection between PC1 and PC2 via both NAT routers is established.

  A case will be described in which the NAT router under the control of PC1 is a pattern 1 type router, and the NAT router under the control of PC2 is a pattern 2 or pattern 3 type router. Also in this case, the destination port number in both transmissions between PC1 and PC2 is different from the destination port number when the packet was transmitted in the first connection attempt, but for PC1, the source port number converted this time is , The same as the source port number converted in the first connection attempt. That is, even in this second connection attempt, the transmission source port number related to PC1 is converted to “30000”. In this case as well, the source addresses related to PC1 and PC2 converted by both NAT routers are not changed. Therefore, “destination port number: 30000” in packet transmission from PC2 to PC1 matches “source port number: 30000” in packet transmission from PC1 to PC2. That is, the destination port number by PC2 and the transmission source port number of PC1 coincide with each other in the first connection attempt. As a result, this second connection attempt establishes a communicable connection between PC1 and PC2 via both NAT routers that were not established in the first connection attempt.

  Further, a case will be described where the NAT router under the control of PC1 is a pattern 2 or pattern 3 type router, and the NAT router under the control of PC2 is a pattern 1 type router. Also in this case, the destination port number in both transmissions between PC1 and PC2 is different from the destination port number when the packet was transmitted in the first connection attempt, but for PC2, the source port number converted this time is It is the same as the source port number converted in the first connection attempt. That is, even in this second connection attempt, the transmission source port number related to PC2 is converted to “40000”. In this case as well, the source addresses related to PC1 and PC2 converted by both NAT routers are not changed. Therefore, “destination port number: 40000” in transmission of a packet from PC1 to PC2 matches “source port number: 40000” in transmission of a packet from PC2 to PC1. In other words, the destination port number by PC1 and the transmission source port number of PC2 are in agreement with each other in the first connection attempt. As a result, this second connection attempt establishes a communicable connection between PC1 and PC2 via both NAT routers that were not established in the first connection attempt.

  In this way, the NAT router under the control of PC1 or the NAT router under the control of PC2 is a type 1 router, and in the first connection attempt, the mutual connection between PC1 and PC2 via both NAT routers. Even if a communicable connection has not been established, the second connection attempt establishes a communicable connection between PC1 and PC2 via both NAT routers.

[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. In step S2, the server SV determines whether or not there are two or more client terminals TM waiting for connection (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. 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 sends all client terminals TM waiting for connection in step S3. Send a connection start instruction. 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 or not a notification of the estimated port number of the connection destination and the connection destination address has been received from the server SV in step C4. Each client terminal TM continues to determine “No” in step C4 until notification of the connection destination guess port number and connection destination address arrives, and notifies the connection destination guess port number and connection destination address. wait.

  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 estimated port number and connection destination address to all the client terminals TM. Specifically, the server SV obtains an estimated port number by adding “+1” to the source port number of the packet received from each client terminal TM, and sets the source address of the received packet as the connection destination address. And Then, the estimated port number and connection destination address relating to each client terminal that is a communication partner are transmitted to all 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 estimated port number and the connection destination address receives the estimated port number and the connection destination address from the server SV, and in step C4, the estimated port number and the connection destination. The address is received, “Yes” is determined, and the process proceeds to Step C5. In step C5, the estimated port number and connection destination address of the partner client terminal TM notified from the server SV are set as the first destination port number and destination address, and the port obtained by subtracting “+1” from the estimated port number The number and the connection destination address are set as the second destination port number and the destination address. Then, the client terminal TM uses the same predetermined source port number and source address as in the case of step C3, and uses the set first destination port number and destination address and the set second destination port number. Then, by sending trial packets (trial data) to the destination address in this order, connection with the partner client terminal TM is attempted. The transmission of the trial packet to the first destination port number and the destination address corresponds to the first connection trial described above, and the transmission of the trial packet to the second destination port number and the destination address corresponds to the second connection trial described above. Corresponding to

  In addition to the transmission of the trial packet for the first destination port number and the destination address and the transmission of the trial packet for the second destination port number and the destination address, the client terminal TM transmits the first destination port as described above. Three or more connections may be attempted using a plurality of port numbers before and after the number and the notified connection destination address. The front and rear port numbers are, for example, several port numbers obtained by adding “+1”, “+2”, “+3”,... To the first destination port number (the estimated port number notified from the server SV). And several port numbers obtained by subtracting “+2”, “+3”... From the first destination port number. In this case as well, the client terminal TM transmits a trial packet using the same source port number and source address as in step C3. 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 may change the source port number to the estimated port number notified from the server SV that is not in use and the ports before and after the port number smaller by “+1”. Therefore, in this case, the trial packet may not reach the partner client terminal TM in the trial of the first and second destination port numbers.

  After the processing in step C5, each client terminal TM determines in step C6 whether or not a trial packet from the partner client terminal TM to be connected has arrived. In a state where the trial packet from the partner client terminal TM has not arrived, each client terminal TM determines “No” in Step C6, and proceeds to Step C7. In step C7, the client terminal TM determines whether or not a predetermined maximum time 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 C7 and returns to step C6 until the trial packet from the partner client terminal TM arrives or the maximum time Until the time elapses, the processes of steps C6 and C7 are repeatedly executed.

  When a trial packet arrives during the cyclic processing in steps C6 and C7, each client terminal TM determines “Yes” in step C6 and proceeds to step C8. In step C8, 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 C7 and proceeds to Step C9. In step C9, each client terminal TM determines whether or not a packet transmission trial by the process of step C5 has been performed a predetermined maximum number of times. When the maximum number of trials has not been performed, the client terminal TM makes a “No” determination at step C9 and proceeds to step C10. In Step C10, each client terminal TM notifies the server SV of a connection retry, returns to Step C2, and repeatedly executes the connection retry including Steps C2 to C7, C9, and C10 described above. When the maximum number of attempts to send a packet is made, each client terminal TM determines “Yes” in step C9, notifies the server SV that the connection has failed in step C11, 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 embodiment, the server SV receives the trial packet transmitted from each client terminal TM in step S4, and the transmission source port used for transmitting the trial packet in step S5. A port number larger by “+1” than the number is notified to the other client terminal TM as an estimated port number. Each client terminal TM uses the same source port number as the source port number used for transmitting the trial packet to the server SV in the first connection attempt in step C5, and the estimated port notified from the server SV. The connection to the partner client terminal TM is tried using the number as the destination port number. In this first connection attempt, if the NAT router NR that controls each client terminal TM is the router of the pattern 2 or pattern 3 described above, the address of the server SV is different from the address of the partner client terminal TM. The transmission source port number related to the client terminal TM is increased by “+1” from the transmission source port number used for transmitting the trial packet to the server SV in step C3. Therefore, if the NAT router NR that controls each client terminal TM is the router of the pattern 2 or pattern 3 described above, the client terminals TM are connected to be communicable with each other.

  However, if the NAT router NR that controls the partner client terminal TM is a router of the type of pattern 1 described above, the sender port number of the partner is used for transmitting the trial packet to the server SV in step C3. Since the port number is the same as the source port number, the connection to the partner client terminal TM under the control of the pattern 1 type NAT router NR is not established. However, each client terminal TM uses the same source port number as the source port number used for transmitting the trial packet to the server SV in the second connection attempt in step C5, and the estimated port notified from the server SV. The port number smaller by “+1” than the number is used as the destination port number, and the connection to the partner client terminal TM is tried. In this case, since the source port number is not changed by the NAT router NR that is pattern 1, each client terminal TM may establish a connection to the other client terminal TM that is under the control of the NAT router NR of pattern 1. it can. As a result, according to the above-described embodiment, the NAT router NR that dominates the client terminal TM is of any type of patterns 1 to 3 and does not require processing for determining the type of the NAT router NR, and can directly communicate. Will be able to.

  Further, as in the above embodiment, each client terminal TM sequentially changes the estimated port number notified from the server SV and the port number smaller by “+1” as the destination port number (for example, by the UDP hole punching method). Function), the NAT router NR that controls the client terminal TM can be changed to the patterns 1 to 3 by changing the function on the server SV side without changing the processing function on each client terminal TM side. Even if it is a simple type, it becomes possible to communicate directly. According to this, it is not necessary to change the functions of many client terminals TM, and the communication system is easily improved.

[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 derived, and the derived estimated port number is notified to the partner client terminal TM. However, the server SV may transmit the transmission source port number of the client terminal TM itself, which is transmitted from the client terminal TM and converted by the NAT router NR, to the partner client terminal TM as an estimated port number. In this case, each client terminal TM performs a first connection attempt using a port number obtained by adding “+1” to the estimated port number (source port number itself) transmitted from the server SV as a first destination port number, and thereafter In addition, a second connection attempt is made with the estimated port number (the source port number itself, which is a port number smaller by “+1” than the first destination port number) transmitted from the server SV as the second destination port number. You just have to do it.

  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. You may make it notify. Then, the client terminal TM makes a first connection attempt using the port number obtained by converting the estimated port number notified according to the rule as the first destination port number, and is smaller by “+1” than the first destination port number. The second connection attempt may be performed using the port number as the second destination port number. In short, the server SV receives a packet transmitted by each client terminal TM, and determines an estimated port number that directly or indirectly represents the source port number from the source port number used for transmitting the packet. It suffices to notify each client terminal TM of the estimated port number related to the client terminal TM to be a communication partner. On the other hand, each client terminal uses the estimated port number notified from the server SV to “+1” from the transmission source port number used for transmission of data to the packet to the server SV by the client terminal TM of the communication partner. A port number that is larger than the first destination port number by making a first connection attempt using the derived port number as the first destination port number, and a port number that is smaller by “+1” than the first destination port number. The second connection trial may be performed as a number. Note that, in the first connection attempt and the second connection attempt to the communication partner client TM by each client terminal TM, the same source port number as that used for transmission of the packet to the server SV is used. .

  In the above embodiment, the server SV estimates the port number obtained by adding “+1” to the source port number converted and used by the NAT router NR when sending a packet from the client terminal TM to the server SV. The number is determined and notified to the partner client terminal TM. 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.

  Considering both the case where the conversion of the source port number by the server SV is performed sequentially and the case where the conversion is not performed sequentially, the data received at step S4 in step S5 in FIG. The source port number of the partner client terminal used for transmission is different from the source port number when the source port number is changed by the NAT router (corresponding to the increase / decrease value). The estimated port number may be estimated and notified to each client terminal TM. In this case, in the first connection attempt, each client terminal TM transmits a packet to the other client terminal TM with the other party's estimated port number notified from the server SV as the destination port number. In the next second connection attempt, each client terminal obtains the estimated port number of the other party notified from the server SV (the same as the destination port number in the first connection attempt) and the change in the transmission source port number. And deriving a port number equal to the transmission source port number of the partner client terminal used for transmitting the data received in step S4, and sending the packet to the partner client terminal TM using the derived port number as the destination port number. Send.

  Further, as described in the modification, the server SV transmits 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 other client terminal TM as the estimated port number. It can also be sent. Also in this modification, when considering the case where the transmission source port number conversion is performed sequentially and the case where the conversion is not performed sequentially, each client terminal TM performs the first connection attempt and the second connection. The trial is done as follows. In the first connection attempt, when the estimated port number notified from the server SV (that is, the transmission source port number related to the partner client terminal at the time of packet transmission to the server) and the transmission source port number are changed by the NAT router. The source port number of the partner client terminal TM when changed by the NAT router is derived as the destination port number using the change in the source port number (corresponding to the increase / decrease value), and the derived destination A packet is transmitted to the other client terminal TM using the port number. In the second connection attempt, the estimated port number notified from the server SV (that is, the transmission source port number related to the partner client terminal at the time of packet transmission to the server) is used as the destination port number to the partner client terminal TM. Send the packet.

  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 (6)

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 are the first NAT router and In a communication system communicating with each other via the second NAT router,
The first terminal includes first transmission means for transmitting data to the server via the first NAT router in order to notify a source port number to the second terminal via the server,
The second terminal includes second transmission means for transmitting data to the server via the second NAT router in order to notify the first terminal via the server of a source port number;
The server
Data receiving means for receiving data respectively transmitted to the server by the first transmitting means and the second transmitting means;
A first estimated port number related to the first terminal is estimated from a transmission source port number used for data transmission by the first transmitting unit received by the data receiving unit, and the estimated first estimated port number is Notifying the second terminal via the second NAT router, and a second guess related to the second terminal from the source port number used for data transmission by the second transmission means received by the data reception means Port number estimating means for estimating a port number and notifying the estimated second estimated port number to the first terminal via the first NAT router;
The first terminal further includes:
First port number receiving means for receiving the second estimated port number notified by the port number estimating means;
A second trial based on the second estimated port number received by the first port number receiving means, using the same source port number as that used for transmitting data to the server by the first transmitting means. The transmission source port number used for transmitting data to the server by the second transmission means is a change in the transmission source port number when the transmission source port number is changed by the NAT router. Trying to connect to the second terminal by sending data to the second terminal via the first NAT router and the second NAT router, with the second trial port number being different only by the destination port number , and
After the trial of connection to the second terminal with the second trial port number as the destination port number, the same source as the source port number used for data transmission to the server by the first transmission means A fourth trial port number based on the second estimated port number received by the first port number receiving means using a port number, the source used for transmitting data to the server by the second transmitting means A first attempt is made to connect to the second terminal by transmitting data to the second terminal via the first NAT router and the second NAT router using a fourth trial port number equal to the port number as the destination port number . And trial means,
The second terminal further includes:
Second port number receiving means for receiving the first estimated port number notified by the port number estimating means;
A first trial based on the first estimated port number received by the second port number receiving means, using the same source port number as that used for transmission of data to the server by the second transmitting means The transmission source port number used for transmitting data to the server by the first transmission means is a change of the transmission source port number when the transmission source port number is changed by the NAT router. A connection to the first terminal is attempted by transmitting data to the first terminal via the second NAT router and the first NAT router, with a first trial port number that is different only by the destination port number , and
After the trial of connection to the first terminal with the first trial port number as the destination port number, the same source as the source port number used for transmission of data to the server by the second transmission means A third trial port number based on the first estimated port number received by the second port number receiving means using a port number, the source used for transmitting data to the server by the first transmitting means A second attempt is made to connect to the first terminal by transmitting data to the first terminal via the second NAT router and the first NAT router with a third trial port number equal to the port number as the destination port number . A communication system comprising trial means. The communication system according to claim 1 ,
The first estimated port number is a transmission source port number used for transmitting data to the server by the first transmission means. The transmission source port number when the transmission source port number is changed by a NAT router is used. The second estimated port number is different from the source port number used for the transmission of data to the server by the second transmission means, the source port number is determined by the NAT router. A communication system, characterized in that the port number is different by the amount corresponding to the change of the source port number when changed. The communication system according to claim 1 or 2 ,
When the source port number is changed by the NAT router, the change of the source port number is “+1”,
The first guess port number is a port number larger by “+1” than the source port number used for transmitting data to the server by the first sending means, and the second guess port number is A communication system having a port number larger by “+1” than a transmission source port number used for transmitting data to the server by the second transmission means. 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 are the first NAT router and In a communication method in a communication system that communicates with each other via the second NAT router, before the first terminal and the second terminal communicate with each other,
The first terminal transmits data to the server via the first NAT router in order to notify the second terminal via the server of a source port number;
The second terminal transmits data to the server via the second NAT router to notify the first terminal of the source port number via the server;
The server
Receiving data transmitted from the first terminal to the server, and receiving data transmitted from the second terminal to the server;
A first estimated port number related to the first terminal is estimated from a source port number used for data transmission by the received first terminal, and the estimated first estimated port number is passed through the second NAT router. And inferring a second estimated port number related to the second terminal from the source port number used for data transmission by the received second terminal, and Informing the first terminal of the estimated port number via the first NAT router;
The first terminal further includes:
Receiving the second guess port number notified from the server;
A second trial based on the received second estimated port number using the same source port number as the source port number used for transmitting data to the server for notifying the second terminal of the source port number The source port number used to transmit data from the second terminal to the server for notifying the first terminal of the source port number is changed by the NAT router. The second trial port number that is different by the change in the source port number when the transmission is performed is used as the destination port number, and data is transmitted to the second terminal via the first NAT router and the second NAT router, thereby Attempt to connect to device and
After the trial of connection to the second terminal with the second trial port number as the destination port number, the same source as the source port number used for data transmission to the server by the first transmission means A fourth trial port number based on the second estimated port number received by the first port number receiving means using a port number, the source used for transmitting data to the server by the second transmitting means Trying to connect to the second terminal by sending data to the second terminal via the first NAT router and the second NAT router, with the fourth trial port number equal to the port number as the destination port number;
The second terminal further includes:
Receiving the first guess port number notified from the server;
A first trial based on the received first estimated port number using the same source port number as the source port number used for transmitting data to the server for notifying the first terminal of the source port number The source port number used to transmit data from the first terminal to the server for notifying the second terminal of the source port number is changed by the NAT router. By transmitting data to the first terminal via the second NAT router and the first NAT router, with a first trial port number that is different by the change of the source port number when the transmission is performed as a destination port number. Attempt to connect to device and
After the trial of connection to the first terminal with the first trial port number as the destination port number, the same source as the source port number used for transmission of data to the server by the second transmission means A third trial port number based on the first estimated port number received by the second port number receiving means using a port number, the source used for transmitting data to the server by the first transmitting means Trying to connect to the first terminal by sending data to the first terminal via the second NAT router and the first NAT router with a third trial port number equal to the port number as the destination port number A characteristic communication method. 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 are the first NAT router and A communication system communicating with each other via the second NAT router,
Before the first terminal and the second terminal communicate with each other,
The first terminal is
Sending data to the server to inform the second terminal of the source port number via the server;
Receiving a second guess port number related to the second terminal notified from the server;
Using the same source port number as the source port number used for data transmission to the server, the first NAT port is a second trial port number equal to the second guessed port number notified from the server. The data is transmitted to the second terminal via the router and the second NAT router, and then at least the received second guess port number and the source port when the source port number is changed by the NAT router Using the changed number, a fourth trial port number equal to the transmission source port number used to transmit data to the server by the second terminal is derived, and the derived fourth trial port number is addressed. By transmitting data to the second terminal via the first NAT router and the second NAT router as a destination port number, Attempts to connect to the terminal, and the second terminal,
Sending data to the server to notify the first terminal via the server of the source port number;
Receiving a first guess port number related to the first terminal notified from the server;
Using the same source port number as the source port number used for transmitting data to the server, the first NAT port number equal to the first estimated port number notified from the server is used as the destination port number to the second NAT. The data is transmitted to the first terminal via the router and the first NAT router, and then at least the received first guess port number and the source port when the source port number is changed by the NAT router A third trial port number equal to the source port number used for transmitting data to the server by the first terminal is derived using the changed number, and the derived third trial port number is addressed By transmitting data to the first terminal via the second NAT router and the first NAT router as a destination port number, A server in a communication system attempts to connect to the terminal,
Data receiving means for receiving data transmitted from the first terminal to the server and receiving data transmitted from the second terminal to the server;
The transmission source port numbers of the first terminal and the second terminal used for transmitting the data received by the data reception means are the transmission source port numbers when the transmission source port number is changed by the NAT router, respectively. A port number that differs by the change of the first guess port number and the second guess port number, and notifies the second guess port number to the second terminal, and the second guess port number A server comprising port number estimation means for notifying a 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 are connected to the first NAT router. And a communication system communicating with each other via the second NAT router,
Before the first terminal and the second terminal communicate with each other,
The first terminal is
Sending data to the server to inform the second terminal of the source port number via the server;
Receiving a second guess port number related to the second terminal notified from the server;
Using the same source port number as the source port number used for data transmission to the server, the first NAT port is a second trial port number equal to the second guessed port number notified from the server. The data is transmitted to the second terminal via the router and the second NAT router, and then at least the received second guess port number and the source port when the source port number is changed by the NAT router Using the changed number, a fourth trial port number equal to the transmission source port number used to transmit data to the server by the second terminal is derived, and the derived fourth trial port number is addressed. By transmitting data to the second terminal via the first NAT router and the second NAT router as a destination port number, Attempts to connect to the terminal, and the second terminal,
Sending data to the server to notify the first terminal via the server of the source port number;
Receiving a first guess port number related to the first terminal notified from the server;
Using the same source port number as the source port number used for transmitting data to the server, the first NAT port number equal to the first estimated port number notified from the server is used as the destination port number to the second NAT. The data is transmitted to the second terminal via the router and the first NAT router, and then at least the received first guess port number and the source port when the source port number is changed by the NAT router A third trial port number equal to the source port number used for transmitting data to the server by the first terminal is derived using the changed number, and the derived third trial port number is addressed By transmitting data to the first terminal via the second NAT router and the first NAT router as a destination port number, A computer program applied to a server in a communication system attempts to connect to the terminal,
A data receiving step of receiving data transmitted from the first terminal to the server and receiving data transmitted from the second terminal to the server;
The transmission source port numbers of the first terminal and the second terminal used for transmitting the data received in the data reception step are the transmission source port numbers when the transmission source port number is changed by the NAT router, respectively. A port number that differs by the change of the first guess port number and the second guess port number, and notifies the second guess port number to the second terminal, and the second guess port number A computer program comprising a port number estimating step of notifying the first terminal.

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