JP2010004449A - Communicating system, client apparatus, and server apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize restoration of connection by a simple procedure in a short time, when the connection between clients and a server is disconnected. <P>SOLUTION: When each client 1 detects disconnection of the connection, the client transmits a connection connecting request for requesting a new set up for connection together with an apparatus number to the server 2 without transmitting a connection closing request for requesting a closing process as to the disconnected connection, and the server administrates the connection in association with the apparatus number, and when it receives the connection connecting request together with the apparatus number from any of the clients without receiving the connection closing request, it determines a connection to be an object. cancels the determined connection, and performs processing to set up a new connection with the client which is the transmission source of the connection connecting request. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a communication system in which a connection is established between a server device and a client device, and data communication is performed using the connection.
More specifically, for example, a connection using a TCP (Transmission Control Protocol) socket is established between a plurality of client devices connected to one server device in a DSRC (Dedicated Short Range Communication) system. The present invention relates to a client / server apparatus using a TCP socket that performs data communication according to.

  In a client / server system using TCP / IP, there is a method of establishing a connection via a TCP port between a server and a client using a socket interface and performing data communication by the connection.

  In such a system, when a data transmission / reception error during connection establishment at the TCP port or an error due to disconnection of a communication cable occurs, automatic connection close processing by detection using an OS (Operating System) timeout period or a human server And restarting the software by resetting the client.

  However, such a method has problems such as an OS-dependent error detection timeout time reduction limit and a software restart time required for a reset operation.

When such an error occurs, a connection establishment request is automatically output, a connection is established, and there is no need for error handling, and there is a method for shortening the time until connection recovery (for example, Patent Document 1). ).
Japanese Patent Laid-Open No. 5-346896 (page 4, first figure)

However, in the system described in Patent Document 1, the execution sequence and each subsystem are very complicated.
In addition, it may be difficult to implement complex execution sequences and a large number of subsystems due to hardware restrictions and software restrictions. Especially in DSRC application systems, it is difficult to implement with TCP socket interface. There is a problem that there is.

  One of the main objects of the present invention is to solve the above-described problems, and the main object of the present invention is to realize a mechanism that can restore a connection in a short time by a simple processing procedure.

A communication system according to the present invention includes:
In a communication system comprising a server device and one or more client devices that perform data communication with the server device using a connection established between the server device,
Each client device
When it is detected that the connection with the server device is disconnected, a new connection close processing request for requesting the close processing for the disconnected connection is sent to the server device A connection setting request for requesting connection setting is transmitted together with identification information of the own device,
The server device
Manage the connection set up with the client device in association with the identification information of the corresponding client device,
When a connection setting request is received together with identification information of the client device without receiving the connection close processing request from any client device, the client device that is the transmission source of the connection setting request based on the received identification information The connection set between and is determined, the determined connection is discarded, and a process for setting a new connection with the client device that is the transmission source of the connection setting request is performed. .

  According to the present invention, since the connection can be recovered without sending a connection close processing request, the connection can be recovered in a short time by a simple processing procedure.

Embodiment 1 FIG.
In the present embodiment, a mechanism for automatically detecting data transmission / reception errors from connection monitoring and automatically restoring the connection without requesting a connection close process from the client to the server will be described.

  FIG. 1 shows a TCP layer configuration of a client device 1 (hereinafter also simply referred to as a client) and a server device 2 (hereinafter also simply referred to as a server) constituting the communication system according to the present embodiment, and a single server 2. On the other hand, a plurality of (N) clients are connected.

  In this system, the clients 1a to 1n use, for example, an OS provided with TCP as the 3rd layer and 4th layer protocol of the OSI (Open Systems Interconnection) reference model, and Ethernet (registered trademark) as the 2nd layer protocol. The server 2 also uses an OS having TCP and Ethernet (registered trademark) as a similar protocol, and is connected via the transmission path 3.

The server 2 and the clients 1a to 1n construct a one-to-N system. However, in the state of data communication or the like, the server 2 discriminates each client by a specific device number (client identification information), and N logic Have a connection port.
The server 2 generates a communication thread when the client comes to connect, and the generated communication thread is in charge of communication with the client. Further, the management of the client device number is handled by another thread (device number management thread), and the thread is determined by the device number.
In the present embodiment, each client is identified by a device number. However, if it is identification information, it does not have to be a device number. For example, each client is identified by an IP address, a MAC (Media Access Control) address, or the like. May be determined.

  When the clients 1a to 1n monitor the communication status of the data transmission / reception of the connection between the client and the server and the data communication unit 11 that transmits / receives data via the connection and detect an error in data transmission / reception due to a cable disconnection or the like A connection monitoring unit 12 that performs a close process of its own connection and instructs the connection control unit 10 to issue a connection connection request (connection setting request) to the connection control unit 20 in parallel with the close process, and a connection monitoring unit 12 The connection control unit 10 continues to issue a connection connection request to the connection control unit 20 of the server 2 until the connection is established, and a TCP layer (not shown).

The server 2 generates a data management thread at the same time as generating a communication thread in response to a connection request from the data communication unit 21 that transmits and receives data via the connection and the connection control unit 10 of the client 1, and manages the data Connection control that monitors the device number of the client included in the thread, and when a client with the same device number issues a connection connection request, discards the old connection and creates a connection with the client of the same device number that has newly connected Part 20 and a TCP layer (not shown).
The data communication unit 21 sends a connection connection request (connection setting request) for requesting setting of a new connection when the connection with a certain client is disconnected in addition to transmission / reception of normal data. This is an example of a connection setting request receiving unit that receives the number (identification information).

  With such a configuration, data communication is performed between the clients 1a to 1n and the server 2 via communication ports (TCP ports) at both ends of the connection established by the socket interface.

The operation of the communication apparatus according to the present embodiment will be outlined below.
When each of the clients 1a to 1n detects that the connection with the server 2 is disconnected, the client 1a to 1n transmits a connection close processing request for requesting close processing for the disconnected connection to the server 2. Instead, a connection request for setting a new connection is transmitted together with the device number of the own apparatus.
The server 2 manages the connection set with the client in association with the device number of the corresponding client, and does not receive a connection close processing request from any client, and the client device When the connection connection request is received together with the number, the connection set with the client that is the source of the connection connection request is determined based on the received device number, the determined connection is discarded, and the connection connection request Process for setting a new connection with the client of the transmission source.

  Next, an operation example in a normal TCP / IP protocol will be described as a premise for explaining an operation example of the clients 1a to 1n and the server 2 according to the present embodiment.

1) The server is always passive and the client is active.
2) When the connection between the client and the server is disconnected and reconnected for some reason, first, a connection close processing request is transmitted from the client to the server.
3) Next, the server performs connection close processing only after receiving the connection close processing request. That is, unless a connection close processing request is received from the client, the connection port in the server remains open.
4) When the connection close process in the server is completed, the server notifies the client that the connection close has been completed.
5) Upon receiving a notification of the end of connection close from the server, the client transmits a connection connection request to the server.
6) The server sets up a connection only after receiving the connection connection request, and communication processing such as data transmission becomes possible.

Next, connection recovery processing when a data communication error occurs between the clients 1a to 1n and the server 2 in the communication system according to the present embodiment will be described using the flowchart of FIG.
In the following description, the case where the connection between the client 1a and the server 2 in FIG. 1 is disconnected will be described as an example.

  During normal data communication, a connection between a communication thread in charge of communication and a data thread in charge of data management (device number management thread) is established between the client 1a and the server 2, and the data communication unit 11 is connected through the connection. Data transmission / reception is performed by the data communication unit 21 (“OK” in step 100 and step 200 in FIG. 2).

Next, for example, when a data transmission / reception error occurs in the TCP port of the client 1a, the connection monitoring unit 12 that monitors data transmission / reception on the connection by the client 1a determines that data transmission / reception is not performed. Then, disconnection of the connection is detected (“connection disconnection” in step 101), and the connection on the client 1a side is closed (step 102). And it will be in a waiting state until a connection is reconnected (until a port is set in the client 1a).
When the connection is reconnected in the client 1a, the connection control unit 10 detects the connection reconnection (“connection connection” in step 102), and issues a connection connection request to the connection control unit 20 of the server 2 (step 103). ). At this time, the connection control unit 20 immediately transmits a connection connection request to the server 2 via the data communication unit 11 without transmitting a connection close processing request required in the normal TCP / IP processing sequence. .

The server 2 receives a connection connection request from the connection control unit 10 of the client 1a and generates a communication thread in charge of communication in the connection control unit 20 and a data thread in charge of data management including the device number. Since no connection close processing request has been received from 1a, there remains a thread having the same device number before data transmission / reception, so that the connection control unit 20 determines that a client having the same device number has come to the connection connection request ( Step 201).
Next, the connection control unit 20 discards the open port (old thread) and discards the old connection (step 202), opens a new port with the same device number (new thread), and sets the same communication thread. A new connection by the data management thread is established with the client 1a (step 203), and the latest requested TCP port is set as positive (“OK” in step 200).
Further, the connection monitoring unit 12 of the client 1a detects the connection connection performed in step 203, and communication sequence processing such as data transmission / reception is performed again from the client 1a side.

  As described above, after the latest connection is established between the client 1 and the server 2, data transmission / reception recovered from the data transmission / reception error is performed by the latest connection ("OK" in step 100 and step 200).

If the connection between the client and the server is cut for some reason (FIG. 3A), the normal TCP / IP protocol omits the connection close processing request as shown in FIG. 3B. If a client with the same device number requests reconnection, the connection port remains open as described above, and the server communication software or other processing software hangs up and cannot be reconnected. A phenomenon occurs. Even if the client requests connection reconnection with a connection close processing request for a disconnected connection, it takes time to recover the system (detection of reconnection).
On the other hand, in this embodiment, as shown in FIG. 3C, when a client having the same device number comes to connect with the application software of the server 2, for example, an old thread (communication thread and communication thread). A device number management thread is discarded, and a new thread (communication thread and device number management thread) is generated for the same device number to establish a connection.

  Even when a data transmission / reception error occurs on the server 2 side, automatic recovery similar to the above is performed, and data transmission / reception can be performed through the latest connection.

  Even in this case, detection of the error by the connection monitoring unit 12 of the client 1a is possible because it can be determined that data transmission / reception is not performed because data transmission / reception on the connection is monitored. Then, the error is detected, the connection on the client 1a side is closed (step 102), and then a communication connection request is issued to the connection control unit 20 of the server 2 to the connection control unit 10 (step 103).

  Similarly, the server 2 receives a connection request from the connection control unit 10 of the client 1a and generates a communication thread in charge of communication in the connection control unit 20 and a data thread in charge of data management including the device number. Since the client 1 has not received a connection close processing request, there remains a thread having the same device number before data transmission / reception, so it is determined that the client having the same device number has come to the connection request (step 201), and the old connection (Step 202), a new connection is established by the same communication thread and data management thread (step 203), the latest requested TCP port is made positive (“OK” in step 200), and the client 1 and server After establishing the latest connection between the two, the latest connection The ® down, it is possible to perform data transmission and reception to recover from data transmission errors ( "OK" in step 100 and step 200).

  A connection error may be caused by disconnection of the communication cable of the transmission path 3 connected to the client and the server. However, even in this case, the connection can be recovered in this system by the communication cable on the client side or the server side.

That is, even when the communication cable is disconnected on the client side, the connection monitoring unit 12 of the client 1 monitors the data transmission / reception state on the connection, and can cope with the recovery flow similar to the data transmission / reception error. In other words, when the communication cable is disconnected, the connection monitoring unit 12 detects the disconnection of the connection, and when the communication cable is connected, the connection control unit 10 issues a connection close processing request in the same manner as when a data transmission / reception error occurs. The server 2 transmits a connection connection request without transmitting, and the server 2 performs the processing after step 201 in FIG.
Further, disconnection of the communication cable on the server side can be handled by the same recovery flow as that of the data transmission / reception error for the same reason as described above.

  As described above, according to the communication system according to the present embodiment, even when a data transmission / reception error occurs on the connection on the client or server side, the old connection is automatically discarded with a simple sequence and software structure. Since a new connection is established, there is no need for error handling, and the connection recovery time is greatly reduced.

  Even if the communication cable is disconnected, the old connection is automatically discarded and a new connection is established automatically with a simple sequence and software structure, eliminating the need for error handling and greatly reducing connection recovery time. Is made.

  In addition, a connection recovery process can be appropriately performed even in a client having a configuration in which a connection close process request cannot be transmitted in accordance with the TCP / IP standard due to hardware and software restrictions.

Finally, a hardware configuration example of the client 1 and the server 2 shown in the present embodiment will be described.
FIG. 4 is a diagram illustrating an example of hardware resources of the client 1 and the server 2 illustrated in the present embodiment.
The configuration in FIG. 4 is merely an example of the hardware configuration of the client 1 and the server 2, and the hardware configuration of the client 1 and the server 2 is not limited to the configuration illustrated in FIG. There may be.

In FIG. 4, the client 1 and the server 2 include a CPU 911 (also referred to as a central processing unit, a central processing unit, a processing unit, a processing unit, a microprocessor, a microcomputer, and a processor) that executes a program.
The CPU 911 is connected to, for example, a ROM (Read Only Memory) 913, a RAM (Random Access Memory) 914, a communication board 915, a display device 901, a keyboard 902, a mouse 903, and a magnetic disk device 920 via a bus 912. Control hardware devices.
Further, the CPU 911 may be connected to an FDD 904 (Flexible Disk Drive), a compact disk device 905 (CDD), a printer device 906, and a scanner device 907. Further, instead of the magnetic disk device 920, a storage device such as an optical disk device or a memory card (registered trademark) read / write device may be used.
The RAM 914 is an example of a volatile memory. The storage media of the ROM 913, the FDD 904, the CDD 905, and the magnetic disk device 920 are an example of a nonvolatile memory. These are examples of the storage device.
A communication board 915, a keyboard 902, a mouse 903, a scanner device 907, an FDD 904, and the like are examples of input devices.
The communication board 915, the display device 901, the printer device 906, and the like are examples of output devices.

  As shown in FIG. 1, the communication board 915 is connected to a network. For example, the communication board 915 may be connected to a LAN (local area network), the Internet, a WAN (wide area network), or the like.

The magnetic disk device 920 stores an operating system 921 (OS), a window system 922, a program group 923, and a file group 924.
The programs in the program group 923 are executed by the CPU 911 using the operating system 921 and the window system 922.

The RAM 914 temporarily stores at least part of the operating system 921 program and application programs to be executed by the CPU 911.
The RAM 914 stores various data necessary for processing by the CPU 911.

The ROM 913 stores a BIOS (Basic Input Output System) program, and the magnetic disk device 920 stores a boot program.
When the client 1 and the server 2 are activated, the BIOS program in the ROM 913 and the boot program in the magnetic disk device 920 are executed, and the operating system 921 is activated by the BIOS program and the boot program.

  The program group 923 stores programs for executing the functions described as “˜units” in the description of the present embodiment. The program is read and executed by the CPU 911.

In the description of the present embodiment, the file group 924 includes “determination of”, “calculation of”, “comparison of”, “detection of”, “generation of”, “discarding of”, Information, data, signal values, variable values, etc. indicating the results of the processing described as “connection of”, “monitoring of”, “setting of”, “registration of”, “request for”, etc. Parameters are stored as items of “˜file” and “˜database”.
The “˜file” and “˜database” are stored in a recording medium such as a disk or a memory. Information, data, signal values, variable values, and parameters stored in a storage medium such as a disk or memory are read out to the main memory or cache memory by the CPU 911 via a read / write circuit, and extracted, searched, referenced, compared, and calculated. Used for CPU operations such as calculation, processing, editing, output, printing, and display.
Information, data, signal values, variable values, and parameters are stored in the main memory, registers, cache memory, and buffers during the CPU operations of extraction, search, reference, comparison, calculation, processing, editing, output, printing, and display. It is temporarily stored in a memory or the like.
Also, the arrows in the flowcharts described in this embodiment mainly indicate input / output of data and signals, and the data and signal values are the memory of the RAM 914, the flexible disk of the FDD904, the compact disk of the CDD905, and the magnetic disk device. It is recorded on a recording medium such as a 920 magnetic disk, other optical disks, minidisks, and DVDs. Data and signals are transmitted online via a bus 912, signal lines, cables, or other transmission media.

  In addition, what is described as “˜unit” in the description of the present embodiment may be “˜circuit”, “˜device”, “˜device”, and “˜step”, “˜”. “Procedure” and “˜Process” may be used. That is, what is described as “˜unit” may be realized by firmware stored in the ROM 913. Alternatively, it may be implemented only by software, or only by hardware such as elements, devices, substrates, and wirings, by a combination of software and hardware, or by a combination of firmware. Firmware and software are stored as programs in a recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD. The program is read by the CPU 911 and executed by the CPU 911. In other words, the program causes the computer to function as “to part” of the present embodiment. Alternatively, the procedure or method of “˜unit” in the present embodiment is executed by a computer.

  As described above, the client 1 and the server 2 described in the present embodiment include a CPU as a processing device, a memory as a storage device, a magnetic disk, a keyboard as an input device, a mouse, a communication board, and a display device as an output device and a communication board. As described above, the function indicated as “to part” is realized by using these processing device, storage device, input device, and output device.

1 is a diagram illustrating a configuration example of a communication system according to Embodiment 1. FIG. FIG. 3 is a flowchart showing an operation example in the communication system according to the first embodiment. The figure which shows the process example in the communication system which concerns on Embodiment 1, and a normal TCP / IP protocol. FIG. 3 is a diagram illustrating a hardware configuration example of a client device and a server device according to the first embodiment.

Explanation of symbols

  1 client device, 2 server device, 3 transmission path, 10 connection control unit, 11 data communication unit, 12 connection monitoring unit, 20 connection control unit, 21 data communication unit.

Claims (5)

In a communication system comprising a server device and one or more client devices that perform data communication with the server device using a connection established between the server device,
Each client device
When it is detected that the connection with the server device is disconnected, a new connection close processing request for requesting the close processing for the disconnected connection is sent to the server device A connection setting request for requesting connection setting is transmitted together with identification information of the own device,
The server device
Manage the connection set up with the client device in association with the identification information of the corresponding client device,
When a connection setting request is received together with identification information of the client device without receiving the connection close processing request from any client device, the client device that is the transmission source of the connection setting request based on the received identification information The connection set between and is determined, the determined connection is discarded, and a process for setting a new connection with the client device that is the transmission source of the connection setting request is performed. Communications system. The client device is
When it is detected that a data communication error has occurred with the server device and the connection with the server device has been disconnected, the connection close processing request is transmitted to the server device. 2. The communication system according to claim 1, wherein the connection setting request is transmitted together with identification information of the own device. The client device is
When it is detected that an error has occurred in the communication cable connected to the server device and the connection with the server device has been disconnected, the server device can be used when the error of the communication cable is resolved. The communication system according to claim 1, wherein the connection setting request is transmitted together with identification information of the own device without transmitting the connection close processing request. In a client device that performs data communication with the server device using a connection established with the server device,
A connection monitoring unit for monitoring a connection set between the server device and detecting disconnection of the connection;
When connection disconnection is detected by the connection monitoring unit, a request for setting a new connection is sent to the server device without sending a connection close processing request for requesting close processing for the disconnected connection. And a connection control unit that transmits a connection setting request to be transmitted together with identification information of the own device. In a server device that sets a connection with one or more client devices and performs data communication with each client device using the set connection,
The client apparatus sends a connection setting request for requesting a new connection without receiving a connection closing process request for requesting a closing process for the disconnected connection from the client apparatus that has detected that the connection is disconnected. A connection setting request receiving unit that receives the identification information of
It is received when the connection set with the client device is managed in association with the identification information of the corresponding client device, and the connection setting request and the identification information are received by the connection setting request receiving unit. Based on the identified information, the connection setting with the client device that is the source of the connection setting request is determined, the determined connection is discarded, and a new connection is established with the client device that is the source of the connection setting request. And a connection control unit that performs processing for setting a secure connection.

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