JP2002217938A - Relay server and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system which can readily conduct connection between terminals within different local systems. SOLUTION: A terminal 11 logs in a relay server 4, and the terminal 11 updates the connection information and notifies the update to a relay server 5, when communication with the relay server 4 is available. Likewise, a terminal 21 logs in the relay server 5, and the terminal 21 updates the connection information and notifies the update to the relay server 4, when communication with the relay server 5 is available. When a connection request from the terminal 11 to the terminal 21 is transmitted to the relay server 4, the relay server 4 refers to the connection information to estimate the connection state of the terminal 21, and the fact that the terminal 21 is connected to the relay server 5. If the terminal 21 can be communicated, the relay server 4 transfers the connection request to the relay server 5, and then the relay server 5 transfers the transferred connection request to the terminal 21. Hereinafter, the relay servers 4 and 5 relay communications between the terminal 11 and the terminal 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a communication system in which a plurality of network devices and a plurality of relay servers are connected by a network, and a relay server suitable for use in such a communication system.

[0002]

2. Description of the Related Art FIG. 7 is an explanatory diagram showing an example of a general system using the Internet. In the figure, 1 and 2 are local systems, 3 is the Internet, 11, 12, and
21, 22 are terminals, 13, 23 are gateways, 14,
24 is a LAN. The local system 1 is a terminal 1
1, a terminal 12, a gateway 13, and the like are connected by a LAN 14. Gateway 13 is L
It is connected to the Internet 3 together with the AN 14,
The Internet can be used from various network devices such as the terminals 11 and 12 on the LAN 14. The same applies to the local system 2;
2, a gateway 23 and the like are connected by a LAN 24. The gateway 23 is connected to the Internet 3 together with the LAN 24.
The Internet can be used from various network devices such as the terminals 21 and 22 above. Of course, in each of the local systems 1 and 2, various other devices may be connected by the LANs 14 and 24.

In such a system, one or more global IP addresses are usually assigned to the local systems 1 and 2, but a global IP address is assigned to each network device in the local systems 1 and 2. Not necessarily. A private IP address is allocated to each network device in each of the local systems 1 and 2, and the gateways 13 and 23 use a function such as NAT or IP masquerade to divide the private IP address with the global IP address. Conversion is being performed. Gateway 13 having such an IP address conversion function,
23, for example, in the local system 1, the terminal 11,
12 uses the Internet 3 through the gateway 13. Also in the local system 2, the terminals 21 and 22 use the Internet 3 via the gateway 23.

The gateways 13 and 23 or other network devices have functions such as a firewall and a proxy server, and a configuration is also used in which each terminal uses the Internet 3 via these devices. Improves system safety.

Here, for example, when an attempt is made to access the terminal 11 in the local system 1 from the Internet 3, although the global IP address of the gateway 13 can be known, the private I
The P address cannot be known. Therefore, the terminal 11 cannot be accessed from outside the local system 1 by a normal connection method. In some cases, sites that accept access are restricted by the function of the firewall of the gateway 13 or the like. Of course, the same applies to the terminal 12, and the same applies to the terminals 21 and 22 in the local system 2.

Further, the terminal 11 in the local system 1
Terminal 12, terminal 21 or terminal 2 in the local system 2.
2 has only a client function and does not have a server function for receiving information from another network device. Therefore, the terminals 11, 12, 21, 22
The information cannot be transmitted from the other network device to these terminals unless the second device accesses the other network device.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to facilitate connection from the Internet to a terminal in a local system or connection between terminals in different local systems. And a relay server suitable for use in such a communication system.

[0008]

According to the present invention, in a relay server, communication means capable of communicating with a plurality of network devices and other relay servers, and connection information holding means for holding connection information of the communicable network devices. Wherein the communication unit updates the connection information based on a request from the network device and notifies the other relay server based on the update of the connection information. Further, the communication means updates the connection information in the connection information holding means based on a notification at the time of updating the connection information from the another relay server.

According to the present invention, in a communication system in which a plurality of network devices and a plurality of relay servers are connected by a network, the network device establishes a communication path with any one of the relay servers and communicates with another network device. Communication by making a connection request of
The relay server holds the connection information of the communicable network device, updates the connection information based on a request from the network device, notifies the other relay server, and sends the connection information from another relay server. The connection information is updated based on a notification at the time of updating the connection information.

As described above, when the connection information of the network device connected to each relay server is updated, the connection information is notified to another relay server and the update notification of the connection information is received from another relay server. Thus, the connection information of the network device can be constantly updated and shared. Therefore, even when a connection request is made from a network device to another network device, the relay server can know which relay server the connected network device is connected to and immediately relay the communication. Can be. Also, the network device does not need to be aware of which relay server the connected network device is connected to, and can easily make a connection request. Furthermore, since connection information of network devices connected to other relay servers is also accumulated in the relay server, if the connection information is configured to be able to be referred to from the network device, the connection is established before a connection request is made. It is possible to check the previous state and the like.

The notification at the time of updating the connection information as described above is performed by the updated relay server to all other relay servers, and the relay server can also be configured to relay the notification. . In this case, the relay server is configured to forward the notification to another relay server other than the source server when receiving the notification, and if the received notification is in the past before the notification received so far. It may be configured to discard without updating. This makes it possible to spread the notification while preventing the loop of the notification.

Further, in the present invention, in a communication system in which a plurality of network devices and a plurality of relay servers are connected by a network, a database server for holding the connection information of the network devices and providing the connection information to the relay server Having a communication path with any of the relay servers,
The relay server performs communication by making a connection request with another network device, and the relay server holds the updated connection information in the database server when updating the connection information based on a request from the network device. It is characterized by the following.

As described above, the connection information of the network device connected to each relay server is held in the database server, and the connection information is provided to the relay server. Then, when the connection information is updated, the updated connection information is uploaded to the database server, so that the latest connection information is always held and provided. Therefore, even when a connection request is made from a network device to another network device, the relay server obtains connection information from the database server, so that the connection destination network device is connected to which relay server, It is possible to know whether such a state exists, and if the communication is possible, the communication can be immediately relayed. Also, the network device does not need to be aware of which relay server the connected network device is connected to, and can easily make a connection request. Furthermore, if the connection information is acquired from the database server and configured to be able to be referred to from the network device, it is possible to confirm the state of the connection destination before making a connection request in the network device.

[0014]

FIG. 1 is a block diagram showing a first embodiment of a communication system including a relay server according to the present invention. In the figure, the same parts as those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted. Reference numerals 4 and 5 are relay servers, 41 is a communication unit, and 42 is a connection information holding unit. The relay server 4 and the relay server 5 are connected to the Internet 3,
Each has a global IP address. A login request for the global IP address is received from a network device, and a connection with the network device is maintained to secure a communication path. It is also assumed that a communication path is provided between the relay server 4 and the relay server 5. The network device may be connected to any of the relay servers. In the example shown in FIG. 1, the terminals 11 and 12 in the local system 1 are connected to the relay server 4 via the gateway 13, the terminals 21 and 22 in the local system 2 are connected to the relay server 5, An example is shown. Note that the relay server 4,
5 can maintain a connection with a plurality of network devices.

The relay servers 4 and 5 communicate with each other by relaying data from the Internet or network devices of other local systems using a communication path with such network devices. When a connection request from a network device to another network device or the like is received, if the connection destination has established a communication path with the relay server, data is relayed between the two using the communication path and communication is performed. Do. If the connection destination is communicably connected to another relay server, the relay device relays data between the network device that made the connection request and the other relay server, and further transfers the data to another relay server. Relays the data to the connected network device to realize communication between the network devices.

For example, the relay server 4 can connect to the gateway 13 in the local system 1,
Terminals 11 and 12 cannot be connected. However, if the global IP address of the relay server 4 is used, the gateway 11
It is possible to connect to the relay server 4 via. Accordingly, by making a login request from the terminal 11 or the terminal 12 to the relay server 4, bidirectional communication between the relay server 4 and the terminal 11 or the terminal 12 that has made the login request becomes possible. Similarly, the relay server 5 can connect to the gateway 23 in the local system 2, but cannot connect to the terminals 21 and 22. However, the global IP of the relay server 5
If the address is used, it is possible to connect to the relay server 5 from the terminal 21 or 22 via the gateway 23. Therefore, the relay server 4 is
, A bidirectional communication between the relay server 5 and the terminal 21 or the terminal 22 that has made the login request becomes possible. In addition, relay server 4
The terminal 11 communicates with the relay server 5 by communication.
Terminal 12 and terminal 21 or terminal 22 can communicate with each other via relay server 4 and relay server 5.

The relay server 4 can include, for example, a communication unit 41 and a connection information holding unit 42. The communication unit 41 can communicate with a plurality of network devices and one or more relay servers via the Internet 3. When the communication unit 41 receives the connection request information from the network device communicably connected, the communication unit 41 refers to the connection information in the connection information holding unit 42 according to the connection request information, and connects to the connection destination network device. A relay server is determined, and a connection request is relayed directly to the relay server or via another relay server, and data transfer with the network device that has requested the connection is relayed. For example, the terminals 11 are communicably connected to each other by the communication unit 41, and upon receiving connection request information with the terminal 21 connected to the relay server 5, data is transferred between the terminal 11 and the communication unit 41. Together with the communication unit 41
And data transfer between the server and the relay server 5. Further, by performing communication with the terminal 21 in the relay server 5,
The communication between the terminal 11 and the terminal 21 is substantially realized. Of course, communication between two network devices connected to the relay server 4 is also possible. Also, it is possible to secure a plurality of connections with one network device, and it is possible for one network device to communicate with a plurality of network devices using a plurality of connections.

The structure of the relay server 5 is as follows.
Can be configured similarly to Of course, the number of relay servers is not limited to two, and more relay servers may be provided on the Internet. Also, each relay server may not be able to connect to all relay servers,
A connection mode in which the relay server is connected to a target relay server via one or more relay servers may be used.

The communication unit 41 processes a login request from a network device as described above, a connection request to another network device, a communication termination after connection, a logout, and the like. When it changes, the connection information in the connection information holding unit 42 corresponding to the network device is updated, and another relay server is notified that the connection information has been updated. This notification can include, for example, updated connection information of all network devices connected to the relay server, updated connection information of changed network devices, and the like. Also, it is preferable to include the update date and time and information for specifying the relay server that has performed the update.

The communication unit 41 receives a notification sent from another relay server, compares it with the connection information held in the connection information holding unit 42, and updates the connection information according to the received notification if the connection information is newer. . Then, the received notification is transferred to a relay server other than the transmission source of the notification. If the received notification is a past one before the connection information held in the connection information holding unit 42,
The connection information holding unit 42 is discarded without being updated, and is not transferred to another relay server. Thereby, the connection information held in the connection information holding unit 42 is managed so as to be always the latest, and the transfer of the notification is prevented from forming a loop, and is transferred so as to reach all the relay servers. Can be.

The connection information holding section 42 holds connection information of network devices connectable to each relay server. The connection information includes, for example, information such as a user ID and a connection state, and can manage a user (network device) that can communicate via the relay server, manage a communication state, and the like. FIG. 2 is an explanatory diagram of an example of information including the connection information held by the connection information holding unit 42. In the example illustrated in FIG. 2, connection information including information such as a user ID, a type, an attribute, and a state as well as information such as a server name and an IP address as information unique to the relay server, and the last update date and time of the connection information Is stored in the connection information storage unit 42. The type can hold information on the type of the network device, for example, information such as whether the device is a client terminal or a device such as a FAX or a printer. The attribute can hold various types of information attached to the type information. For example, the example shown in FIG. 2 shows an example in which an attribute indicating transmission / reception in file units is added. As the status information, for example, information indicating whether or not the user is logged in, whether or not communication with another network device has been performed after the login, and the like can be held. Of course, various other information may be included as the connection information.

It is desirable that the last update date and time be added when notifying another relay server when the connection information is updated. The relay server that has received the notification can determine whether the information is the latest information based on the added last update date and time.

The connection information for each network device shown in FIG. 2A can be registered in advance by specifying the network device connected to the relay server. As a result, it is possible to reject a login request or the like from a device other than the registered network device, thereby ensuring security. Further, security can be improved by holding authentication data such as a password.

The connection information holding section 42 holds connection information sent from another relay server in addition to connection information of network devices connected to the relay server 4. These can be stored as connection information for each relay server, for example, as shown in FIG.
By managing the connection information for each relay server in this way, when a connection request from a network device to another network device is received, the relay server to which the connection destination network device is connected can be immediately determined. . It is also possible to know the status of the connection destination network device. For example, if the connection destination network device is not logged in, the connection request can be made an error without relaying to another relay server. .

FIGS. 3 and 4 are sequence diagrams showing an example of a communication procedure in the first embodiment of the communication system including the relay server of the present invention. The communication procedure shown in FIGS. 3 and 4 is executed using TCP / IP, and connects to a relay server, maintains connection, requests connection to a terminal, transfers data to a terminal, terminates connection with a terminal, and relays. The connection with the server is terminated. FIG. 3 shows a portion of connection with the relay server, maintenance of the connection, and termination of the connection with the relay server. FIG. 4 shows portions of a connection request to the terminal, data transfer to the terminal, and termination of the connection with the terminal. Is shown in

Here, as an example, a case where communication is performed between the terminal 11 in the local system 1 and the terminal 21 in the local system 2 in FIG. 1 is shown. The terminal 11 is registered as a user with the relay server 4 in advance, and the terminal 21 is registered with the relay server 5 as a user. As the registration information, for example, FIG.
Can be the information of each item of the connection information shown in FIG.
In addition, a password or the like may be registered for authentication. The connection information is regarded as an update of the connection information at the time of registration, for example, and is notified from the relay server in which the network device is registered to another relay server. As a result, the relay server 4 and the relay server 5 share the connection information of each other.

The terminal 11 is connected to the relay server 4 via the gateway 13 at (1), for example, after activation or when instructed by the operator, logs in, and performs a TCP / IP connection with the relay server 4 (connection 1). )
To establish. Since the terminal 11 is a network device in the local system 1, the terminal 11 cannot directly communicate with the relay server 4, but can connect to the relay server 4 by logging in from the terminal 11 which is a client.
Since the TCP / IP connection enables bidirectional data communication, communication from the terminal 11 to the relay server 4 and from the relay server 4 to the terminal 11 can be performed.

After the connection 1 is established, the terminal 11 sends the user ID to the relay server 4 in (2). Relay server 4
Checks whether the received user ID is held in the connection information holding unit 42 as connection information. Note that the terminal 11
It is preferable to perform authentication using, for example, a password together with the user ID. By this authentication, connection with an unspecified third party can be avoided, and security can be ensured. If the connection information is not registered or the authentication fails, the relay server 4 sends a negative response to the terminal 11 or disconnects the connection 1 as it is. If the authentication is successful, an acknowledgment is made in (3) and the connection information of the terminal 11 is changed to the login state. In (4), the connection information is updated to another relay server (here, the relay server 5). Notice. In response to the notification, the relay server 5 updates the connection information of the relay server 4 held by the relay server 5 to match the connection information held by the relay server 4.

When a TCP / IP connection with the relay server 4 is established and authentication is obtained, the connection (connection 1) is periodically maintained in the relay server 4 in (5) in order to maintain the connection (connection 1). Is transmitted, and a confirmation response is obtained from the relay server 4 in (6). As a result, the connection is maintained, and it is confirmed that the relay server is operating normally. In this way, the connection 1 that allows communication between the terminal 11 and the relay server 4 is maintained.

Similarly, at (1 '), the terminal 21 connects to the relay server 5 via the gateway 23, logs in, and establishes a TCP / IP connection (connection 2) with the relay server 5. Since the terminal 21 is also a network device in the local system 2, the terminal 21 cannot directly communicate with the relay server 5.
Connection to the relay server 5 is possible by logging in from 1. By the connection 2, from the terminal 21 to the relay server 5,
Further, communication from the relay server 5 to the terminal 21 can be performed.

After the connection 2 is established, the terminal 21 sends the user ID to the relay server 5 at (2 '). The relay server 5 checks whether the received user ID is registered. In addition, it is preferable to perform authentication using, for example, a password together with the user ID of the terminal 11. By this authentication, connection with an unspecified third party can be avoided, and security can be ensured. If the connection information is not registered or the authentication fails, the relay server 5 sends a negative response to the terminal 21 or disconnects the connection 2 as it is. If the authentication is successful, in (3 '),
An acknowledgment is made and the connection information of the terminal 21 is changed to the login state, and in (4 '), the update of the connection information is notified to another relay server (here, the relay server 4). Upon receiving this notification, the relay server 4 updates the connection information of the relay server 5 held by the relay server 4 so that the connection information matches the connection information held by the relay server 5.

When the TCP / IP connection with the relay server 5 is established and the authentication is obtained, the connection to the relay server 5 is periodically made at (5 ') to keep the connection (connection 2). The holding command is transmitted, and a confirmation response is obtained from the relay server 5 in (6 '). As a result, the connection is maintained, and it is confirmed that the relay server is operating normally. Thus, terminal 2
Maintain a communicable connection 2 between 1 and the relay server 5.

The connection between the terminal 11 and the relay server 4 and the connection between the terminal 21 and the relay server 5 may be made at any time before the communication between them. In this way, if a terminal in the local system is connected to any of the relay servers, communication can be performed between the terminals. FIG. 4 shows a sequence when communication is performed between terminals.

When a request to connect to the terminal 21 is issued from the terminal 11, the terminal 11 makes a connection request to the relay server 4 by designating the user ID of the terminal 21 to be connected to the relay server 4 in (11). Note that the user ID of the terminal 21 to be connected can be specified by an arbitrary method, such as acquiring the user ID in advance, or checking and specifying the user ID from a list of users logged in from the relay server 4.

The relay server 4 refers to the connection information held in the connection information holding unit 42 and specifies to which relay server the network device having the user ID specified by the terminal 11 is connected. I do. Note that the relay server 4 sends an error response to the terminal 11 if the connection information corresponding to the specified user ID cannot be obtained or if the network device corresponding to the specified user ID has not logged in. To return.

When the relay server 4 specifies the relay server 5 to which the terminal 21 specified by the connection request is connected,
In (12), a connection request to the terminal 21 is sent to the specified relay server 5. The relay server 5 receives the connection request transferred from the relay server 4 and, in (13), a connection including information indicating that there is a connection request to the terminal 21 and a user ID of the terminal 11 requesting the connection. Send a request notification.

The terminal 21 stores that the connection used for transmitting the connection request notification is used for connection with the terminal 11, and returns an acceptable response in (14).
If the connection is rejected, an error is returned. The relay server 5 transfers the response from the terminal 21 to the relay server 4 in (15). At this time, in the case where the response is that the terminal 21 receives the connection request, the connection information for the connection 2 of the terminal 21 is updated and the fact that the connection 2 is used for communication with the terminal 11 is stored. Notify another relay server (relay server 4).

On the other hand, the relay server 4 returns the response from the terminal 21 transferred from the relay server 5 to the terminal 11 at (16). If the response from the terminal 21 is a response to the effect that the connection request is received, the connection information on the connection 1 of the terminal 11 is updated and the fact that the connection 1 is used for communication with the terminal 21 is stored. Is notified to another relay server (relay server 5). Terminal 2
When receiving the response from the terminal 11, the terminal 11 that has received the response accepts the response, stores the connection being used (connection 1) as being used for communication with the terminal 21.

The relay server 4 receives the notification from the relay server 5 and updates the connection information of the relay server 5 held by the relay server 4 to match the connection information held by the relay server 5. Also, the relay server 5 receives the notification from the relay server 4 and updates the held connection information of the relay server 4 so as to match the connection information held by the relay server 4. The connection information update notification in (17) and (18) may be given first depending on the communication path.

After confirming the communication between the terminal 11 and the terminal 21 in this way, the data is actually transmitted after (26). In the example illustrated in FIG. 4, after the communication between the terminal 11 and the terminal 21 is determined to be performed, a connection request from another network device is received or a connection request to another network device is performed. For this purpose, a new TCP / IP connection is established with the relay servers 4 and 5, respectively. That is, the terminal 11
Logs in the relay server 4 in (19) and establishes a TCP / IP connection (connection 3) with the relay server 4, and the terminal 11 sends the user ID to the relay server 4 in (20). The relay server 4 authenticates the terminal 11 based on the received user ID and the like, and returns a response in (21). At the same time, the connection information for the terminal 11 is updated and another relay server (here, the relay server 5) is notified in (22). The relay server 5 receives the notification from the relay server 4 and updates the connection information of the relay server 4. In order to maintain the new connection 3, the relay server 4 periodically transmits a connection holding command from the terminal 11 to the relay server 4 at (24), and the relay server 4
In 5), a response is returned to the terminal 11.

Similarly, the terminal 21 logs in to the relay server 5 at (19 ') and performs TCP / IP communication with the relay server 5.
The connection (connection 4) is established, and the terminal 21 sends the user ID to the relay server 5 at (20 '). The relay server 5 determines the terminal 21 based on the received user ID and the like.
Is authenticated, and a response is returned in (21 '). At the same time, the connection information for the terminal 21 is updated, and another relay server (here, the relay server 4) is notified in (23). The relay server 4 receives the notification from the relay server 5 and updates the connection information of the relay server 5. The relay server 5 periodically updates (2
In 4 '), the terminal 21 transmits a connection hold command to the relay server 5 and the relay server 5 returns a response to the terminal 21 in (25'). If there is no need to secure such an empty connection, the steps (19) to (25) or (19 ') to (25') are not necessary. Also, when a plurality of connections have already been secured, these steps need not be performed.

According to the above (11) to (18), the terminal 1
After confirming that communication is performed between the terminal 1 and the terminal 21,
In (26), the terminal 11 transmits data to be transmitted to the terminal 21 to the relay server 4 using the connection 1. The relay server 4 receives the data from the terminal 11, and (27)
, The received data is transferred to the relay server 5. The relay server 5 receives the data transferred from the relay server 4 and transmits the data to the terminal 21 using the connection 2 in (28). The terminal 21 receives the data from the terminal 11 transmitted from the relay server 4 using the connection 2, and transmits a response to the terminal 11 to the relay server 5 in (29). The relay server 5 transfers the response to the terminal 11 transmitted by the terminal 21 to the relay server 4 in (30). The relay server 4 receives the response to the terminal 11 from the terminal 21 transferred from the relay server 5, and transmits the received response to the terminal 11 using the connection 1 in (31).

In this way, the terminal 11 and the relay server 4
Relaying data between the relay server 4 and the relay server 5 using the connection 1 between the relay server 4 and the relay server 4 and the communication between the relay server 4 and the relay server 5 and the connection 2 between the terminal 21 and the relay server 5. , The communication between the terminal 11 and the terminal 21 can be performed. The data transfer from the terminal 11 to the terminal 21 according to (26) to (31) may be repeated a plurality of times. Further, data transfer from the terminal 21 to the terminal 11 may be performed.

When the data transfer between the terminal 11 and the terminal 21 is completed, an end notification is sent from the terminal 11 or 21. Here, it is assumed that the notification is made from the terminal 11, and in (32), the terminal 11 sends an end notification to the terminal 21 in connection 1
To the relay server 4 using The relay server 4 transfers the end notification to the terminal 21 received from the terminal 11 to the relay server 5 in (33). The relay server 5 receives the end notification to the terminal 21 transferred from the relay server 4, and transmits the end notification to the terminal 21 using the connection 2 in (34). The terminal 11 that has transmitted the end notification transmits an open notification indicating that the connection 1 has become free to the relay server 4 in (35).
The terminal 21 that has received the end notification also transmits an open notification indicating that the connection 2 has become free to the relay server 5 at (35 '). As a result, the relay server 4 updates the connection information of the connection 1 from the one for communication between the terminal 11 and the terminal 21 to an empty state, and notifies the other server (here, the relay server 5) of the fact in (36). Notice. Further, the relay server 5 transmits the connection information of the connection 2 to the terminal 11 and the terminal 21.
Is updated to empty for communication between and (36 ')
At the other relay server (here, the relay server 4). Each of the relay servers 4 and 5 that has received the connection information update notification updates the connection information according to the notification. In addition,
In this example, 21 does not respond to the end notification, but a response may be returned.

The connection 1 and the connection 2 released as described above periodically perform the connection holding command and the response as shown in (5), (6) or (5 ') and (6'). Between the terminal 11 and the relay server 4 and the terminal 21
The connection between the server and the relay server 5 is maintained. At this time, the connection 1 and the connection 3 are secured between the terminal 11 and the relay server 4. Similarly, connection 2 and connection 4 are secured between the terminal 21 and the relay server 5. The connection may be left as it is, or these connections may be disconnected when connection 1 and connection 2 are released. Of course, the connection 1 and the connection 2 may be kept, and the connection 3 and the connection 4 may be disconnected.

Returning to FIG. 3, for example, when the terminal 11 turns off the power or stops connecting to the relay server 4,
In (7), the terminal 11 notifies the relay server 4 of logout. At this time, if a plurality of connections are secured, any of the connections may be used. Then, the terminal 11 disconnects all connections. here,
First, the connection 1 is disconnected in (8). In addition, since the connection 3 is also provided at the time of communication with the terminal 21 in FIG. 4, the connection 3 is disconnected in (9) and the processing is ended.

The relay server 4 receives the logout notification from the terminal 11 and updates the connection information.
At 0), the update of the connection information is notified to another relay server (here, relay server 5). The relay server 5
The connection information of the relay server 4 is updated based on the notification. Further, the relay server 4 disconnects the connections 1 and 3 when the terminal 11 logs out. Note that the terminal 21 can log out to the relay server 5 in the same manner.

By executing the above-described procedure, communication can be performed even when each or one of them is a network device in the local system. Even when each network device is connected to another relay server, communication can be performed without any trouble. At this time, there is no need to know which relay server is connected, and communication can be performed easily.

The procedure for connecting to the relay server 4, maintaining the connection, requesting a connection to the terminal, transmitting data to the terminal, terminating the connection with the terminal, and terminating the connection with the relay server as described above is as follows. , It is possible to configure so that commands and data exchanged by the application protocol running on the upper layer are kept transparent and have no effect, and communication can be performed using the existing application protocol as it is It is possible.

In the above example, a case has been described in which the relay server to which the connection requesting network device is connected can directly communicate with the relay server to which the connection destination network device is connected. However, the present invention is not limited to such a configuration. For example, one or more relay servers may be interposed between two relay servers. In this case, each relay server may perform the routing.

The notification when the connection information is updated may be made mutually in the above example. If direct communication can be performed with all relay servers, the updated relay server may notify each of the other relay servers. However, if there is a relay server that cannot perform direct communication, some measure is necessary, such as relaying the notification by the relay server. One method for disseminating a notification regardless of the connection mode of a plurality of relay servers is that each relay server is configured to transfer a notification to a relay server capable of direct communication other than the source of the notification. I just need. As a result, a notification can be sent if the communication path is connected regardless of the route. But in this case,
Information may be circulated through a loop. In order to prevent this, the update date and time in the notification may be referred to, the old notification before the update date and time of the stored connection information may be discarded, and further transfer may not be performed.

FIG. 5 is an explanatory diagram of an example of a method of transferring a notification between relay servers. In the figure, 51 to 54 are relay servers. In this example, the relay servers 52 are the relay servers 51 and 5
Communication channels have been established with the relay server 5 and the relay server 5.
A communication path is also established between 3, 54. For example, when the relay server 51 updates the connection information and performs notification,
The relay server 51 notifies the relay server 52. The relay server 52 updates the connection information based on the notification, and transfers the notification to another communicable relay server except the relay server 51 that is the transmission source of the notification, that is, the relay servers 53 and 54. The relay server 53 updates the connection information according to the received notification, and transfers the notification to another communicable relay server, that is, the relay server 54, excluding the relay server 52 that is the transmission source of the notification. Similarly, in the relay server 54, the connection information is updated according to the notification received from the relay server 52, and the relay server 5 that is the transmission source of the notification is updated.
The notification is forwarded to another communicable relay server excluding 2, that is, the relay server 53.

The relay server 53 receives the notification from the relay server 54, but receives the same notification from the relay server 52 and discards the notification before the update date and time and does not perform any further notification. Similarly, the relay server 54 also receives a notification from the relay server 53, but receives the same notification from the relay server 52 and discards the notification before the update date and time, and does not perform any further notification. In this way, the notification can be distributed to all the relay servers, and the notification can be prevented from being looped among the relay servers 52, 53, 54.

FIG. 6 is a block diagram showing a second embodiment of the communication system including the relay server according to the present invention. In the figure,
The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 6 denotes a database server. In the above-described first embodiment, an example has been described in which connection information in each relay server is notified and shared between the relay servers. In this case, the same connection information needs to be held in each relay server. In the second embodiment, an example is shown in which the connection information stored in each relay server is collectively stored in the database server 6 and shared by the relay servers.

The database server 6 holds, for example, connection information as shown in FIG. 2 for each relay server, and provides the connection information in response to an inquiry from the relay server. Further, in response to an update request from the relay server, the connection information of the requesting relay server is updated.

The relay servers 4 and 5 are used to request a login from a network device, a connection request to another network device, a communication termination after connection, a logout, and the like.
When the state of the connection with the network device changes, a request is made to the database server 6 to update the connection information corresponding to the network device. When a connection request is received from a network device, the connection information of the connection destination network device is acquired from the database server 6, and the relay server to which the connection destination network device is connected is determined. At this time, it is possible to determine the connection state of the network device of the connection destination and determine whether communication is possible. Further, before a connection request is made from a network device, the relay server can obtain a list of communicable network devices from the database server 6 and provide the list information to the connected network devices.

The communication procedure in the second embodiment may be substantially the same as the procedure shown in FIGS. 3 and 4, and only the differences will be described here. First, when a TCP / IP connection is established from a network device and authentication is performed based on a user ID or the like, the relay server inquires the database server 6 of connection information or registration information of the network device, and responds to the network device. Authentication can be performed by acquiring connection information. Alternatively, the registration information of the network device may be held in the relay server, and authentication may be performed according to the held registration information. After the authentication, if the connection is permitted, the database server 6 is requested to update the connection information. This operation is the same even when another connection is secured at the time of a connection request.

When a connection request is received from a network device connected to the relay server, the connection information of the connection destination is inquired to the database server 6 to obtain the connection information. According to the acquired connection information, the relay server to which the connection destination network device is connected is determined, and it is checked whether the connection destination network device can communicate. If the connection destination network device can communicate, a connection request is sent to the determined relay server. When the connection destination network device accepts the communication, the relay server to which the connection destination network device is connected and the relay server to which the connection request source network device is connected update the connection information with the database server 6.
Request to. Thereafter, data communication is performed between the network devices.

After the communication is completed, an end notification is transferred between the network devices, and when a connection release notification is received from each network device, the relay server to which each network device is connected updates the connection information with the database server. Request to 6. When the logout is notified from the network device, the relay server requests the database server 6 to update the connection information accordingly.

As described above, by requesting the database server 6 to update whenever the connection state between the network device and the relay server changes, the database server 6 always holds the latest connection information in all the relay servers. Will be done. If this is shared by a plurality of relay servers, communication between network devices can be managed without each relay server holding connection information.

[0061]

As is clear from the above description, according to the present invention, a communication path is secured by previously connecting a network device in a local system to a relay server, and data is transmitted using this communication path. Therefore, data transfer from the Internet to network devices in a local system or data transfer between network devices in different local systems can be realized. In addition, each relay server shares or shares the connection information of the network device, so that regardless of which relay server the network device is connected to, it is possible to know which relay server the connected network device is connected to. There is an effect that communication between network devices can be easily performed without performing.

[Brief description of the drawings]

FIG. 1 shows a first example of a communication system including a relay server according to the present invention.
FIG. 2 is a configuration diagram showing an embodiment.

FIG. 2 is an explanatory diagram of an example of information including connection information held by a connection information holding unit 42;

FIG. 3 shows a first example of a communication system including the relay server of the present invention.
FIG. 21 is a sequence diagram showing an example of a communication procedure at the time of login and logout in the embodiment.

FIG. 4 shows a first example of a communication system including the relay server of the present invention.
FIG. 17 is a sequence diagram showing an example of a communication procedure at the time of a connection request in the embodiment.

FIG. 5 is an explanatory diagram of an example of a method of transferring a notification between relay servers.

FIG. 6 shows a second example of the communication system including the relay server of the present invention.
FIG. 2 is a configuration diagram showing an embodiment.

FIG. 7 is an explanatory diagram showing an example of a system using a general Internet.

[Explanation of symbols]

1,2… Local system, 3… Internet, 4,
5 ... relay server, 6 ... database server, 11, 1
2, 21, 22, ... terminal, 13, 23 ... gateway, 1
4, 24 LAN, 41 communication unit, 42 connection information holding unit, 51 to 54 relay server.

Claims (4)

[Claims] 1. A communication device capable of communicating with a plurality of network devices and another relay server, and a connection information holding device for holding connection information of the communicable network device, wherein the communication device includes the network device. A relay server that updates the connection information based on a request from the server and notifies the other relay server based on the update of the connection information. 2. A communication device capable of communicating with a plurality of network devices and another relay server, and a connection information holding device for holding connection information of the communicable network device, wherein the communication device includes: A relay server for updating the connection information in the connection information holding means based on a notification at the time of updating the connection information from the relay server. 3. In a communication system in which a plurality of network devices and a plurality of relay servers are connected by a network, the network device establishes a communication path with any one of the relay servers, and requests a connection with another network device. The relay server holds connection information of a communicable network device, updates the connection information based on a request from the network device, and notifies another relay server. A communication system for updating the connection information based on a notification at the time of updating the connection information sent from another relay server. 4. A communication system in which a plurality of network devices and a plurality of relay servers are connected by a network, further comprising a database server that holds connection information of the network devices and provides the connection information to the relay server. The network device establishes a communication path with any one of the relay servers, performs a connection request with another network device, and performs communication, and the relay server is configured based on a request from the network device. When updating the connection information, the database server stores the updated connection information.