JP2009044619A - Communication method, network system, storage medium, and network connection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network system simply configured to sufficiently ensure real-time property of data reception in a client even when performing data communication, according to a request command/answer response system, between the client and a server via a low-speed network. <P>SOLUTION: When transmitting the same request command from a client in a fixed cycle, the request command is cached at a server side. Thus, without performing data communication of the request command from the client via a network, an answer response is redirected from the server in a fixed cycle in accordance with the cached request command. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a system for performing data communication in a system in which a response response to a request command is returned between a client and a server connected via a network, and in particular, a communication method, a network system, and a memory with improved real-time characteristics The present invention relates to a medium and a network connection device. Here, an information processing device (computer) on the client side is defined as a client, and an information processing device (computer) for a server is defined as a server.

  In factory automation (FA) or the like, a network system is constructed in which a client 1 and a server 2 are connected via a network 3 and data communication is performed via the network 3 as shown in FIG. In such a network system, for example, as shown in FIG. 10, a command (request command) requesting output of the value of data A stored in the data area of the server 2 is transmitted from the client 1 to the server 2. In many cases, the value of the data A is returned in the form of a response response to the request command from the server 2 receiving the request command to the client 1. Such a data communication form is called, for example, a request command / response response system (see, for example, Patent Documents 1 and 2).

In the FA, the same request command is often repeatedly transmitted from the client 1 at regular intervals so that the data collected by the server 2 is constantly monitored on the client 1 side.
JP 2000-32006 JP JP 2001-168921 A

  However, when the network 3 is constructed by a low-speed communication line laid over a wide area, the time (response delay time; delay time) required from sending a request command to arrival of a response response may increase. Undoubtedly, there is a problem that real-time performance is impaired. In addition, when using an Internet line as a wide area network, communication data is often encrypted to increase security, and the response delay time described above increases due to heavy processing associated with encryption / decryption. There is a problem to say. Therefore, in applications such as state monitoring that requires collecting data in real time using a request command / response response method, there is a problem that it is limited to a high-speed environment such as a local area network.

  The present invention has been made in consideration of such circumstances, and its object is to perform data communication by a request command / response response method between a client and a server via a relatively low speed network such as a wide area network. Therefore, it is an object to provide a communication method capable of performing data communication with sufficiently ensuring the real-time property and a network system with a simple configuration.

  At the same time, it is an object of the present invention to provide a storage medium storing a software program having a function necessary for constructing the network system, and a network connection device having the function.

  In order to achieve the above-described object, the present invention performs data communication between a client and a server connected via a network by a request command / response response method, whereby the data collected by the server is constantly transmitted by the client. In such a case, it is noted that the same request command is often repeatedly transmitted from the client to the server at a constant period. Therefore, the communication method according to the present invention caches the request command when the same request command is received via the network at a constant cycle, and returns a response response at a constant cycle according to the cached request command. It is characterized by.

In the network system according to the present invention, a request command is transmitted from a client to a server via a network, and a response response is returned from the server that has received the request command to the client via the network.
When the same request command is transmitted from the client at a fixed cycle, the request command is cached on the server side, and a response response is returned from the server at a fixed cycle according to the cached request command. It is a feature.

Preferably, the client and the server are respectively connected to the network via a proxy agent having a relay function,
When the same request command is notified from the client in a certain cycle to the client side proxy agent, the server side proxy agent is instructed to cache the request command, and the subsequent request command from the client Preferably, the server-side proxy agent is configured to issue a request command to the server at the predetermined period in place of the client in accordance with the cached request command.

  The server is preferably configured to return a response response in response to a cached request command in anticipation of a response delay time in the network. In the proxy agent on the client side, the same request command may be detected using the value obtained by hash calculation of the contents of the request command as a signature. The hash calculation may be executed by excluding the sequence number included in the request command.

  Further, the functions of the client-side proxy agent and the server-side proxy agent described above may be provided as a storage medium storing software that realizes these functions on a computer. Alternatively, it may be provided as a network connection device having a client-side proxy agent function or a network connection device having a server-side proxy agent function.

  According to the communication method and the network system of the present invention, when the client-side proxy agent detects a state in which the client repeatedly transmits the same request command at regular intervals, the request command is transmitted to the server-side proxy agent. And the subsequent proxy request on the server is stopped, and the server side proxy agent sends a response response to the client at every point of time according to the cached request command, apparently reducing the response delay. can do. In addition, since the same request command is not repeatedly transmitted to the network at regular intervals, it is possible to reduce the traffic amount in the network.

  In particular, when sending a response response from the server to the client, if the response response is sent back in time in anticipation of the response delay time in the network, the client will send the request command in real time at the transmission timing of the request command. Since a response response can be obtained, real-time performance can be ensured with the response delay time substantially zero (0). Therefore, even when data communication is performed by a request command / response response method via a low-speed network, the real-time property can be simply and effectively ensured.

Hereinafter, a communication method according to an embodiment of the present invention and a network system employing the communication method will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a network system according to the present invention. 1 is a client (information processing apparatus on the client side; computer), 2 is a server (information processing apparatus for server; computer), and 3 is a wide area communication line or A network such as an Internet line. The network system according to the present invention connects the client 1 to the network 3 via a proxy response agent (proxy response agent) 4 having a relay function, and also performs a proxy request proxy agent having a relay function. It is constructed by connecting the server 2 to the network 3 via a (proxy request agent) 5. The client 1 and the server 2 are set to perform data communication via the proxy response agent 4 and the proxy request agent 5, respectively. Each of the proxy agents 4 and 5 has a relay function for relaying a request command and a response response between the client 1 or server 2 and the network 3, and a proxy response function and a proxy request function described later. An information processing device (computer).

  The above-described indirect data communication between the client 1 and the server 2 through the proxy response agent 4 and the proxy request agent 5 respectively allows the client 1 to regard the proxy response agent 4 as the server 3. In addition, it is realized by assigning a virtual network address to each of the proxy agents 4 and 5 so that the server 2 can regard the proxy request agent 5 as the client 1.

  The data communication between the proxy agents 4 and 5 via the network 3 is, for example, a request command (communication data) transmitted from the client 1 or a response response (communication data) returned from the server 2 as shown in FIG. ) Is attached with an agent relay control header for controlling the relay of these communication data, and further with a communication protocol header, thereby forming a communication packet of a predetermined format. Preferably, the data communication between the agents 4 and 5 is performed by encrypting communication data contents (packet data) including a request command / response response (communication data) and an agent relay control header.

  In addition to the relay function described above, the proxy response agent 4 monitors a request command transmitted from the client 1 to the server 2, and determines whether or not the same request command is repeatedly transmitted. In the case where the same request command is repeatedly transmitted at a constant period T, a function for detecting the period T is provided. If it is detected that the same request command is repeatedly transmitted over a predetermined period or a predetermined number of times at a constant period T, the relay process of the request command is stopped and the server 2 side Has a function of instructing the cache of the request command.

  On the other hand, the proxy request agent 5 has a cache function for the request command in addition to the relay function described above. When receiving a request command cache instruction from the proxy response agent 4, the cache function includes a request command that has been repeatedly transmitted from the client 1 at a predetermined period T and information on the transmission period T of the request command. It plays a role of writing and saving in a memory (cache memory) (not shown). Further, the proxy request agent 5 has a function of repeatedly notifying the request command to the server 2 on behalf of the client 1 every cycle T according to the cached request command when the request command is cached as described above.

  When the request command cached in this way is output to the server 2, the proxy request agent 5 determines, based on the transmission delay (delay time D) of communication data in the network 3, as will be described later. The same request command is repeatedly output at a constant period T at a timing that is back by the time D corresponding to the delay time. Then, the server 2 considers the request command issued by the proxy request agent 5 as the request command transmitted from the client 1 and returns a response response to the client 1.

  The response response returned from the server 2 in this way is relayed from the proxy request agent 5 via the network 3 and further via the proxy response agent 4 and transmitted to the client 1. Therefore, the client 1 can receive the response response as if there was a response response in real time from the proxy response agent 4 in response to the request command transmitted by itself.

  In the network system constructed in this way, the relay functions of the proxy response agent 4 and the proxy request agent 5 are used, so that basically between the client 1 and the server 2 as shown in FIG. Thus, data communication by the request command / response response method can be performed indirectly. However, in this case, due to the transmission characteristics of the network 3 connecting the proxy response agent 4 and the proxy request agent 5, it can be denied that it takes time (delay time) for the request command transmitted from the client 1 to reach the server 2. Absent. Similarly, it cannot be denied that it takes time (delay time) until the response returned from the server 2 reaches the client 1.

  However, using the same request command detection function by the proxy response agent 4 and the request command cache function by the proxy request agent 5, the relay of the request command issued from the client 1 to the server 2 side is stopped, and instead, By giving the request command cached from the proxy request agent 5 to the server 2, it is not necessary to perform data communication of the request command via the network 3 as shown in FIG. Transmission delay can be eliminated.

  In addition, since it is necessary to perform data communication via the network 3 for the response response returned from the server 2, the transmission delay of itself cannot be avoided. However, as described above, if a transmission delay in the network 3 is anticipated and a response response is output from the server 2 at a timing that is traced back by the transmission delay time, the client 1 apparently responds without a response delay. It becomes possible to receive. However, in order to advance the response response output timing in this way, it goes without saying that the request command cached from the proxy request agent 5 is issued at a timing that goes back in anticipation of the transmission delay time. Yes.

  Therefore, according to the network system constructed in this way, even in an environment where transmission delays in the network 3 cannot be ignored, the client 1 receives the response response in real time without delay from the timing at which the request command is issued. And real-time characteristics can be sufficiently enhanced. Moreover, paying attention to the fact that the client 1 often issues the same request command repeatedly at a certain period T, the request command that is repeatedly issued at a predetermined period T is cached by the proxy request agent 5 on the server 2 side, and thereafter Collecting data at the client 1 by the request command / response response method in real time with simple control of repeatedly returning a response response according to the cached request command without performing data communication of the request command via the network Can do. Therefore, its practical advantage is tremendous.

  Here, the detection process of the same request command included in the proxy response agent 4 and the cache process of the request command in the proxy request agent 5 will be described in a little more detail. Monitoring of the request command transmitted by the client 1 in the proxy response agent 4 is performed by treating the contents of the request command as a signature value and determining whether or not the signature value of the request command repeatedly transmitted is equal. In particular, in the present invention, the content of the request command is hash-calculated, and the calculation result is obtained as a signature value, thereby ensuring the uniqueness of the content of the request command and handling it as small-capacity fixed-length data. Yes.

  In the case where attached information such as a series of sequence numbers (serial numbers) is attached to the request command transmitted from the client 1, only the request command itself excluding the attached information as illustrated in FIG. In other words, hash calculation is performed by masking attached information. The time stamp attached to the request command is managed using the signature value (hash calculation value) obtained in this way as a key. For example, the time difference between the time stamp of the current request command and the time stamp of the previous request command The repetition period T is measured.

  More specifically, the proxy response agent 4 executes a request command monitoring process according to the processing procedure shown in FIG. 5, for example. That is, when the proxy response agent 4 receives the request command from the client 1 (step S1), first, as described above, the content of the request command is hash-calculated and the calculation result is set as the signature value (step S2). Then, the signature table 4a prepared in advance is searched <step S3>, and it is determined whether or not the same signature value is registered in the signature table 4a <step S4>.

  The signature table 4a includes a memory area for storing a time stamp of a request command, a repetition period thereof, the number of times of measurement of the same request command, a measurement completion flag of the same request command, etc. using the signature value as a key. If the signature value obtained in step S2 described above is not registered in the signature table 4a, the signature value is newly registered in the signature table 4a <step S5>. The new registration to the signature table 4a uses the signature value as a key, writes the time stamp value attached to the request command in the time stamp item, and sets the period item and the number of measurement times to zero (0). Is done by resetting to

  In this case, the request command described above is then relay-transmitted toward the server 2 side (proxy request agent 4) <step S6>. Then, it waits for a response from the server 2 side (proxy request agent 4) <step S7>, and when it receives the response, it relays the response to the client 1 <step S8>. This completes the relay of data communication between the client 1 and the server 2 by the request command / response response method.

  On the other hand, if the signature value obtained from the request command is already registered in the signature table 4a described above (step S4), the identity determination (repetition cycle measurement) for the request command has already been completed. Is determined <step S9>. If it is already detected that the same request command has been repeatedly transmitted from the client 1 at a fixed period, the request command is not relayed to the server 4 side, in other words, the request command And waits for a response from the server 4 side as described above <step S7>. The received response response is relayed to the client 1 <Step S8>.

  On the other hand, if the signature value obtained from the request command has already been registered in the signature table 4a, but the repeated transmission period T of the request command has not been obtained, the same as the previous one from the signature table 4a. The time stamp attached to the request command is obtained, the time stamp attached to the current request command is obtained, and the request command repeated transmission cycle T is obtained as a time difference between these time stamps (step S10). Then, it is determined whether or not the repetition cycle T of the request command is registered in the signature table 4a <step S11>. If the transmission cycle T is not registered, the transmission cycle T obtained as described above is used as the signature. The registered contents are updated by writing in the table 4a <step S12>. At this time, the number of measurements N registered in the signature table 4a is incremented.

  Thereafter, the request command received from the client 1 is relayed and transmitted to the server 2 side (proxy request agent 4) <step S6>. Then, it waits for a response from the server 2 side (proxy request agent 4) <step S7>, and when it receives the response, it relays the response to the client 1 <step S8>. This completes the relay of data communication between the client 1 and the server 2 by the request command / response response method.

  On the other hand, when the transmission cycle T is registered in the signature table 4a (step S11), the time difference between the transmission cycle T registered in the signature table 4a and the newly obtained time stamp (transmission cycle T). It is determined whether or not the difference from) is within an allowable error range (step S13). For this error determination, for example, a ratio between the time difference (transmission period T) of the time stamp obtained this time and the transmission period T registered in the signature table 4a is obtained, and whether or not the ratio is equal to or greater than a predetermined determination threshold value. Performed by examining.

  If the deviation of the transmission period T exceeds the allowable error range, the contents of the signature table 4a are initialized, the time stamp newly obtained this time is registered, and the period T and the number of measurements N are set to zero (0). Reset (step S14). Also in this case, the request command received from the client 1 is relay-transmitted to the server 2 side (proxy request agent 4) <step S6>, and a response response from the server 2 side (proxy request agent 4) is waited for < Step S7>, and relay-transmit the received response response toward the client 1 <Step S8>.

  If the difference between the transmission cycle T registered in the signature table 4a and the newly determined transmission cycle T is within an allowable error range, <step S13>, for example, registered in the signature table 4a. The average of the transmission cycle T currently obtained and the transmission cycle (time difference between time stamps) T newly obtained this time is obtained, and this is obtained as the transmission cycle T of the same request command currently measured <step S15>. Then, the repeatability of the same request command is determined by determining whether or not the number of times of measurement N registered in the signature table 4a is equal to or greater than a predetermined number <step S16>. If the measurement number N is less than the predetermined number and repeatability of the same request command is not guaranteed, the current time stamp and the newly obtained period T are registered in the signature table 4a, and the measurement number N is The signature table 4a is updated as an increment <step S17>.

  Also in this case, the request command received from the client 1 is relay-transmitted to the server 2 side (proxy request agent 4) <step S6>, and a response response from the server 2 side (proxy request agent 4) is waited for < Step S7>, and relay-transmit the received response response toward the client 1 <Step S8>. Then, it waits for transmission of the next request command from the client 1.

  Now, as described above, the signature value of the request command transmitted by the client 1 is obtained, and if the identity of the request command and its repetition periodicity are confirmed by referring to the signature table 4a, <step S16> The proxy request agent 5 is instructed to cache the request command <step S18>. Then, after updating the signature table 4a <step S17>, as described above, the request command received from the client 1 is relay-transmitted toward the server 2 side (proxy request agent 4) <step S6>. Then, it waits for a response from the server 2 side (proxy request agent 4) <step S7>, and relays the received response response toward the client 1 <step S8>.

  After instructing the proxy request agent 5 to cache the request command in this way, when a new request command is received from the client 1, the proxy response agent 4 refers to the signature table 4a described above. It is determined whether or not the request command is the same as the request command that is repeatedly transmitted at a predetermined cycle <step S4>. Then, when the repetition cycle of the request command is obtained over a predetermined number of times and the repetition periodicity is guaranteed <Step S9>, the proxy response agent 4 sends the request command received from the client 1 to the server 2 side ( A response response from the server 2 side (proxy request agent 4) is awaited without relay transmission toward the proxy request agent 4), that is, without relaying the request command (step S7). The received response response is relayed to the client 1 <Step S8>.

  Each time the proxy response agent 4 receives a request command issued from the client 1, the proxy response agent 4 determines the identity of the request command according to the above-described processing procedure, and further determines the repeatability at a constant period, thereby determining the proxy request agent. 5 is instructed to cache the request command. Thereafter, the relay of the request command is stopped, and the response response returned from the server 2 at a constant cycle under the management of the proxy request agent 5 is relayed to the client 1. Therefore, the client 1 can surely receive a response from the server 2 in response to a request command transmitted to the server 2 at a constant period T. At this time, if the proxy response agent 4 manages response response relaying according to the sequence number attached to the request command, it is possible to always associate the request command with the response response. There is no possibility of causing any trouble in data communication between the client 1 and the server 2.

  As described above, the proxy request agent 5 that receives a request command cache instruction from the proxy response agent 4 executes the processing function according to the processing procedure shown in FIG. 6, for example. That is, the proxy request agent 5 basically receives the request command from the proxy response agent 4 <step S21>, and determines whether or not the cache command information is included in the request command <step S22>. . If there is no cache instruction, the request command received from the proxy response agent 4 is relayed to the server 2 <Step S23>. Then, a response response sent back by the server 2 in response to this request command is received <step S24>, and the received response response is relayed to the proxy response agent 4 <step S25>. That is, the data communication between the proxy response agent 4 and the server 2 is relayed.

  On the other hand, if the request command notified from the proxy response agent 4 includes cache instruction information (step S22), the request command is cached in the cache memory 5a according to the instruction (step S26). At the same time, information on the repetition period T of the request command obtained by the proxy response agent 4 is acquired. Then, by subtracting the data transmission delay time (transmission delay time) in the network 3 from the repetition period T, a timing that is a predetermined time later than the timing at which the client 1 is expected to transmit the request command next time is set. <Step S27>. In this case, since the proxy response agent 4 stops relaying the request command as described above, the previously cached request command is read instead of the request command from the client 1 at the above timing <step S28>, this request command is transmitted to the server 2 <Step S29>. In this case, the sequence number loaded on the request command is sequentially incremented. Then, a response response returned by the server 2 in response to the transmitted request command is received <Step S30>, and this response response is relayed to the proxy response agent 4 <Step S31>.

  Thereafter, the repetition period T of the request command described above is managed by a timer, and each time the period T elapses <step S32>, the processing from step S28 described above is repeatedly executed. That is, by giving a request command cached at regular intervals to the server 2, the response response is extracted from the server 2 at regular intervals T and relayed to the client 1 side.

  When the proxy request agent 5 functioning in this way and the proxy response agent 4 described above detect the same request command that is repeatedly transmitted from the client 1 at a fixed period, the proxy request agent 5 sends the request command to the proxy request agent 5. It is possible to provide a response response from the server 2 to the client 1 at a constant cycle based on the cached request command without caching and transmitting the request command transmitted by the client 1 via the network 3. In particular, by setting the response response return timing based on the cached request command early in anticipation of transmission delay in the network 3, the response delay from the request command transmission timing to the response response reception timing in the client 1 can be reduced. It can be virtually eliminated (apparently). Therefore, the real time property can be sufficiently increased.

  As for the functions of the proxy response agent 4 and the proxy request agent 5 described above, it suffices if the computer on the client 1 side and the server 2 are respectively incorporated as software programs in the computer as illustrated in FIG. is there. In this case, it is preferable that a software program for executing the functions of the proxy response agent 4 and the proxy request agent 5 is written in a recording medium such as a CD-ROM so that it can be appropriately incorporated into various network systems.

  Alternatively, as shown in FIG. 8, the network connection device having the function of the proxy response agent 4 and the network connection device having the function of the proxy request agent 5 are realized, and these network connection devices are respectively connected to the client computer and the network 3. And between the server computer and the network 3, respectively. In short, the embodiment can be variously modified.

  The present invention is not limited to the embodiment described above. For example, various determination algorithms can be appropriately employed for determining the identity of request commands and determining the periodicity thereof. In addition, here, the one-to-one data communication between the client 1 and the server 2 has been described as an example, but the same applies when performing data communication with a plurality of servers 2 in parallel using a request command / response response method. Can be applied to. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

1 is a schematic configuration diagram of a network system according to an embodiment of the present invention. The figure which shows the example of a format of the packet by which data communication is carried out between a proxy response agent and a proxy request agent. The figure which shows typically the data communication form in the network system shown in FIG. The figure which shows the concept of the signature value calculated | required by hash-calculating the content of a request command. The figure which shows the example of the process sequence which implement | achieves the function of a proxy response agent. The figure which shows the example of the process sequence which implement | achieves the function of a proxy request agent. The figure which shows the implementation example of the network system which concerns on this invention. The figure which shows another example of implementation | achievement of the network system which concerns on this invention. The figure which shows the structure of a general network system. The figure which shows the form of the data communication by the request command / response response system in the network system shown in FIG.

Explanation of symbols

1 Client 2 Server 3 Network 4 Proxy Response Agent 5 Proxy Request Agent

Claims (9)

  A communication method characterized in that when the same request command is received via a network at a constant cycle, the request command is cached and a response response is returned at a constant cycle according to the cached request command. A system for sending a request command from a client to a server via a network and returning a response response from the server that has received the request command to the client via the network,
When the same request command is transmitted from the client at a fixed cycle, the request command is cached on the server side, and a response response is returned from the server at a fixed cycle according to the cached request command. Network system. The client and the server are each connected to the network via a proxy agent having a relay function,
The client-side proxy agent instructs the server-side proxy agent to cache the request command when the same request command is notified from the client in a certain cycle, and the subsequent request command from the client. Has a function to stop
3. The network system according to claim 2, wherein the server-side proxy agent has a function of issuing a request command to the server at the fixed period on behalf of the client in accordance with a cached request command.   3. The network system according to claim 2, wherein when the server responds to the cached request command, the server returns a response response in anticipation of a response delay time in the network.   The network system according to claim 2, wherein the proxy agent on the client side detects the same request command using a value obtained by hash calculation of the contents of the request command as a signature.   The network system according to claim 5, wherein the hash calculation is executed except for a sequence number included in a request command.   A storage medium storing software having the function of the proxy agent on the client side and the function of the proxy agent on the server side according to claim 3.   The network connection apparatus provided with the function of the said proxy agent of the client side of Claim 3.   The network connection apparatus provided with the function of the said server side proxy agent of Claim 3.

Images