JP2013254284A - Method of maintaining connection between networks - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device server system capable of stably using a USB device from a PC irrespective of a communication state between the PC and device server.SOLUTION: Even when a communication pipe between a PC and a device server is unstable, the breakage of a virtual USB device connection is not done, although done in the prior art. Furthermore, a plurality of TCP sessions (communication pipes) are used for the virtual USB device connection; and even when one of the connection pipes becomes unstable, the connection can be maintained by using another communication pipe without interrupting communication that uses the virtual USB device connection. As a result, a reliable device server system capable of performing high-speed processing can be obtained.

Description

  The present invention relates to a device server system, and more particularly to a technique for maintaining a connection between a client and a device server.

A technique called a peripheral device utilization system (hereinafter referred to as device server system) that shares peripheral devices represented by USB devices (hereinafter referred to as USB devices) over a network is known (Non-Patent Document 1). The device server system is a system as shown in FIG. 1, in which a device server 102 to which a USB device 103 (a printer is illustrated in FIG. 1) is connected and a computer such as a PC 101 as a client in the device server system are connected to a network. In the connected environment, the USB device 103 can be used from the PC 101 via the network.

Silex Technology Co., Ltd. Home Page <http://www.silex.jp/products/usbdeviceserver/index.html?init>

In the device server system, the PC 101 can use the USB device 103 as if the USB device 103 was directly connected to itself. Of course, since the USB device 103 is not actually connected directly to the PC 101, the USB device 103 is used based on a virtual connection (described later) via the network.
[Function blocks in the device server system]

  FIG. 2 shows functional blocks of the PC 101 and the device server 102 in the device server system.

  First, the PC 101 will be described. The device driver 201 is software that controls the USB device 103. Specifically, an input / output request (IO Request Packet) to the USB device 103 is generated and issued. Although not shown in the figure, an application such as word processing software can use the USB device 103 via the device driver 201.

  The first capsule processing means 202 is an important technology that supports the device server system. This means encapsulates the input / output request into a network packet so that the input / output request to the USB device 103 issued by the device driver 201 can be transmitted over the network. On the other hand, when a network packet including a response to the input / output request is received, this response is extracted (decapsulated) from the network packet and given to the device driver 201.

  The first TCP communication unit 203 is a so-called TCP stack, and is a unit for performing TCP communication with an arbitrary network device.

  The first network interface 204 is a physical network interface, which is a wired LAN or wireless LAN interface. In the figure, a wired LAN is shown.

  The virtual USB device connection management unit 205 is a unit that manages a virtual connection (hereinafter referred to as a virtual USB device connection) between the device driver 201 of the PC 101 and the USB host controller 212 of the device server 102. The virtual USB device connection can be established and discarded by an instruction from this means. Details of this virtual USB device connection will be described later.

  “Establish virtual USB device connection” means that the virtual USB device connection management unit 205 acquires the device information of the USB device 103 and gives it to the OS (not shown) of the PC 101, whereby the device driver 201 is sent to the PC 101. This means that the virtual USB device connection management means 205 makes the device driver 201 communicable with the first capsule processing means 202. Conversely, “discard the virtual USB device connection” means that the device driver 101 is disconnected from the driver stack of the PC 101.

  Next, the device server 102 will be described. The USB interface 211 is an interface connected to the USB device 103.

  The USB host controller 212 is a device provided in the USB host-side device, and controls the USB device 103 based on an input / output request from the device driver 201.

  The second capsule processing means 213 is a means having the same function as the first capsule processing means 202 described above, and since it exists on the device server 102 side, the name is second. By the operation of these two capsule processing means, USB input / output requests can be mutually transmitted and received between the device driver 101 of the PC 101 and the USB host controller 212 of the device server 102.

  The second TCP communication unit 214 is also a unit having the same function as the first TCP communication unit 203 described above, and since it exists on the device server 102 side, the name is second. Communication by the above-described two capsule processing means is performed on a TCP session (communication pipe) between the first TCP communication means 203 and the second TCP communication means 214.

The second network interface 215 is also a means having the same function as the first network interface 204 described above, and since it exists on the device server 102 side, the name is second.
[Communication path in device server system]

  FIG. 3 shows a communication path when the PC 101 actually controls the USB device 103 via the device server 102.

  As indicated by the arrows in the figure, there are two communication paths between the two. One is between the first TCP communication means 203 and the second TCP communication means 214, which is the TCP session described above. The other is between the device driver 201 and the USB host controller 212, which is the virtual USB device connection described above.

  Normally, when the USB device 103 is directly connected to the PC 101 and used, the device driver 201 is connected to a USB host controller (not shown) originally provided in the PC 101. On the other hand, the device server system uses a TCP session to establish this connection over the network. This is the virtual USB device connection described above. With this connection, it is possible for the device driver 201 to appear as if the USB device 103 is directly connected to the PC 101 over the network. As described above, this virtual USB device connection can be established and discarded by an instruction from the virtual USB device connection management unit 205 of the PC 101.

  When a virtual USB device connection is established by an instruction from the virtual USB device connection management unit 205, the USB device 103 can be recognized on the PC 101. As a result, the input / output request issued from the device driver 201 of the PC 101 can be delivered to the host controller 212 of the device server 102, and the USB device 103 can be finally controlled. Of course, the response data from the USB device 103 is also delivered to the device driver 201 via the virtual USB device connection.

  Needless to say, the device server system is used in a network environment. Of course, the network environment is not always kept in a good state, and the communication quality changes depending on the traffic conditions. In particular, in the case of a wireless LAN, the phenomenon becomes more prominent due to radio wave interference and the like.

  When communication abnormality is detected in the PC 101, the TCP session is discarded by error processing in the PC 101. In this case, the virtual USB device connection that uses the TCP session is also discarded. As a result, the USB device 103 cannot be controlled from the PC 101.

  On the other hand, the communication state is also monitored on the device server 102 side, and when a communication abnormality is detected, the TCP session is discarded. In addition, the device server 102 also performs initialization processing for the USB device 103.

  In general, a conventional device server system disclosed in Non-Patent Document 1 also includes a virtual USB device connection that is incidentally destroyed along with the destruction of a TCP session. The reason is to avoid trouble caused by the device driver 201 that occurs when a response from the USB device 103 cannot be obtained. Originally, the device driver 201 assumes that the USB device 103 is directly connected to the PC 101 itself, and has a structure that does not assume a situation in which communication is impossible for a long time compared to local connection. is there.

  As described above, by destroying the virtual USB device connection accompanying the destruction of the TCP session, it is possible to avoid a problem caused by the device driver 201. On the other hand, however, there was a problem that communication efficiency deteriorated. That is, the communication performed after the discarded TCP session and the virtual USB device connection are restored is not the continuation of the communication performed before the destruction, but the communication is re-executed from the beginning. For example, when a virtual USB device connection is discarded in a situation where a large amount of print data is being transmitted / received, it is necessary to retransmit / receive again from the top of the print data regardless of the progress of communication before the discard.

  The present invention solves this problem. That is, to provide a device server system that can use a USB device from a PC stably and efficiently regardless of the state of communication between the PC and the device server in the device server system.

  A first mode according to the present invention is a communication system between network terminals configured by a plurality of predetermined lower layer communication and a predetermined higher layer communication using one or more of the predetermined lower layer communication. , If a communication abnormality detecting means for detecting a communication abnormality of a predetermined lower layer communication used by the upper layer communication, an upper layer communication discarding means for discarding the upper layer communication, and a communication abnormality detecting means detect an abnormality, And an execution avoidance unit that disables the upper layer communication discarding unit for a predetermined period.

  More preferably, the predetermined period is a period until the predetermined lower layer communication in which the communication abnormality detected by the communication abnormality detecting means has occurred returns to normal communication.

  As a result, when the communication in which the communication abnormality has occurred immediately returns, the communication can be resumed from the middle.

  More preferably, the communication system further includes a communication switching unit that switches a predetermined lower layer communication used by the upper layer communication to another lower layer communication in which no abnormality has occurred when the communication abnormality detecting unit detects an abnormality. The predetermined period is a period until the communication switching by the communication switching means is completed.

  As a result, communication can be resumed immediately from the middle even if the communication abnormality is for a long period of time.

  A second aspect of the present invention is a peripheral device server to which a peripheral device is connected and a peripheral device server system in which a client of the peripheral device server is connected to a network. Virtual peripheral device connection, which is a general connection, a communication abnormality detecting means for detecting a communication abnormality between a client and a peripheral server, a virtual peripheral device connection discarding means for canceling a virtual peripheral device connection, and a communication abnormality detection And an execution avoidance means for disabling the virtual peripheral device connection discarding means for a predetermined period when the means detects an abnormality.

  More preferably, the peripheral device server system further includes a peripheral device initialization unit that initializes the internal state of the peripheral device, and the target that the execution avoidance unit prevents execution is in addition to the virtual peripheral device connection discarding unit, Peripheral device initialization means is included.

  A third embodiment according to the present invention is a peripheral device server to which a peripheral device is connected and a peripheral device server system in which a client of the peripheral device server is connected to a network. A virtual peripheral device that is a virtual connection between a client and a peripheral device using a communication pipe that performs communication using different addresses and one of the plurality of communication pipes. When a communication abnormality detection means for detecting a communication abnormality between the connection and the client and the peripheral server, a virtual peripheral device connection discarding means for discarding the virtual peripheral device connection, and a communication abnormality detection means detect an abnormality, If the execution avoidance means that disables the virtual peripheral device connection discarding means and the communication abnormality detection means detect an abnormality, A communication pipe for use, and a communicating pipe switching means for switching to another communication pipe good communication quality than the communication pipe utilizing current.

  The device server system according to the present invention does not discard the virtual USB device connection as in the prior art even when the communication between the PC and the device server becomes unstable. Furthermore, the device server system according to the present invention uses a plurality of TCP sessions (communication pipes) for virtual USB device connection, so that even if one communication pipe becomes unstable, another communication pipe is used instead. By doing so, communication using the virtual USB device connection can be continued without interruption. As a result, a device server system with high reliability and capable of high-speed processing is obtained.

Embodiments according to the present invention will be described below with reference to the drawings.
[Example 1]
[System overview]

The overall system diagram in the present embodiment is the same as that already described with reference to FIG.
[PC functional blocks]

  Next, functional blocks of the PC 101 will be described with reference to FIG.

  In addition to what has been described with reference to FIG. 2, first communication abnormality detection means 401, first execution avoidance means 402, and communication pipe switching means 403 are added.

  The first TCP communication unit 203 is a unit for establishing a TCP session with the second TCP communication unit 214 of the device server 102. The device server 102 in this embodiment includes two devices as described later. Since it has a network interface, two TCP sessions are established with the device server 102.

  The first communication abnormality detection unit 401 is a unit that monitors communication between the PC 101 and the device server 102 and detects an abnormality. The communication abnormality includes a communication abnormality on a virtual USB device connection in addition to a decrease in throughput and a link disconnection. When a communication abnormality is detected, a first execution avoidance unit 402 and a communication pipe switching unit 403 to be described later are notified to that effect.

  When there is a notification from the first communication abnormality detection unit 401, the first execution avoidance unit 402 instructs a virtual USB device connection management unit 205 described later to prevent execution for a predetermined period. The predetermined period is a period until the communication abnormality returns to normal communication, and specifically, until the communication pipe switching by the communication pipe switching unit 403 described later is completed.

  When the virtual USB device connection management unit 205 receives the execution prevention instruction from the first execution prevention unit 402, the virtual USB device connection between the PC 101 and the USB device 103 is not discarded.

When the communication pipe switching unit 403 receives the notification from the first communication abnormality detecting unit 401, the communication pipe switching unit 403 switches to another communication pipe in which no abnormality has occurred as a TCP session used in the virtual USB device connection. As described above, since there are two communication pipes in this embodiment, such switching can be performed. When the switching is completed, this is notified to the first execution avoiding means 402.
[Function block of device server]

  Next, functional blocks of the device server 102 will be described with reference to FIG.

  In addition to what has been described with reference to FIG. 2, a third network interface 501, second communication abnormality detection means 502, second execution avoidance means 503, and USB device initialization means 504 are added.

  The third network interface 501 is functionally the same as the second network interface 215. The difference is the IP address used in the TCP session. That is, the device server 102 is a device that includes a plurality of network interfaces and can simultaneously operate a plurality of IP addresses. As a result, as described above, two TCP sessions can be used between the PC 101 and the device server 102.

  The second communication abnormality detection unit 502 is functionally the same as the first communication abnormality detection unit 401 described in the functional block of the PC 101. The difference is that the object to be detected is a plurality of network interfaces. When a communication abnormality is detected, a notification to that effect is sent to second execution avoidance means 503 described later.

  When there is a notification from the second communication abnormality detecting means 502, the second execution avoiding means 503 instructs the USB device initializing means 504 described later to avoid execution for a predetermined period. The predetermined period is until the switching of the communication pipe with the PC 101 is completed.

The USB device initialization unit 504 is a unit that initializes the internal state of the USB device 103 via the USB interface 211. Even if the USB device 103 is in the middle of some processing, by executing initialization, the processing can be discarded once and the request can be received again. When the execution avoidance instruction from the second execution avoiding means 503 is received, the initialization process is not performed.
[Operation flow]

  Next, the operation flow of the PC 101 and the device server 102 described so far will be described with reference to FIG.

  First, the operation flow of the PC 101 will be described.

  In step 601, it is determined whether to establish a virtual USB device connection. Specifically, it is determined whether there is an instruction from the user of the PC 101. If so, go to the next step, otherwise repeat the decision.

  In step 602, a communication pipe to be used for connection with the designated virtual USB device is established. In this embodiment, two communication pipes are established. At this time, the virtual USB device connection has not been established yet.

  In step 603, a virtual USB device connection is established. This connection uses one of the two communication pipes established in step 602.

  In step 604, it is determined whether a communication abnormality is detected. If there is an abnormality, go to the next step, otherwise repeat the judgment.

  In step 605, the virtual USB device connection management unit 205 is instructed to avoid discarding the virtual USB device connection until the communication pipe switching is completed.

  In step 606, the communication pipe used for the virtual USB device connection is switched to another communication pipe in which no abnormality has occurred.

  In step 607, the execution avoidance by the first execution avoiding means 402 is released. As a result, the virtual USB device connection management unit 205 can discard the virtual USB device connection. When this step is completed, the process returns to step 604.

  Next, the operation flow of the device server 103 will be described.

  In step 611, it is determined whether a communication abnormality is detected. If there is an abnormality, go to the next step, otherwise repeat the judgment.

  In step 612, the USB device initialization unit 504 is instructed to avoid the initialization of the USB device 103 until the communication pipe switching is completed.

  In step 613, it is determined whether or not the communication pipe has been switched. This is whether or not the processing performed in step 606 on the PC 101 side has been completed. If the switching has been completed, the process proceeds to the next step, and if not, the determination is repeated.

  In step 614, the execution avoidance of the USB device initialization unit 504 is canceled, and the process returns to step 611.

In this embodiment, when a communication pipe abnormality occurs, the virtual USB device connection is not discarded and the USB device 103 is not initialized, and the process is continued using another communication pipe at the same time. . In this way, the device server system can be used stably regardless of the network environment. Further, as described above, the PC 101 is not necessarily triggered by the communication pipe switching process, and the device server 102 side may be the trigger.
[Other embodiments]

  In the first embodiment, a plurality of communication pipes are prepared, and the processing is continued by switching the communication pipes used for virtual USB device connection as needed.

  In addition, the number of communication pipes is not necessarily two, but three or more are prepared, and when a communication abnormality is detected, one of the remaining communication pipes with good communication quality is selected and switched. It may be.

  As another method of effectively using a plurality of communication pipes, there is a method of multiplexing communication. In other words, this is a method in which two or more communication pipes used by one virtual USB device connection are used from the beginning. By sending and receiving the same communication content through multiple communication pipes, processing only the communication that arrives first, and discarding the communication with the same content that was received later, the device is stable regardless of the network environment. A server system can be used.

  Further, without providing a plurality of communication pipes as described in the present embodiment, the virtual USB device connection is not disconnected immediately after detecting a communication abnormality, but is disconnected after a predetermined period (for example, 500 milliseconds). A simpler method is also conceivable. This is because even if an instantaneous communication abnormality occurs, it may return within this predetermined period.

 The communication pipe used in the present invention is naturally applicable not only to a wired network but also to a wireless network or a network in which both are mixed.

The present invention is not limited to the device server system described so far, but also to a communication system between predetermined network terminals configured by predetermined lower layer communication and predetermined upper layer communication using the predetermined lower layer communication. Applicable. In other words, multiple lower layer communications are prepared, and even if one of them becomes unstable, the upper layer communication is not discarded, and only the lower layer communication is replaced as appropriate. Regardless, efficient and stable communication between network terminals is possible. In particular, this is effective for a communication system in which higher-layer communication and lower-layer communication are highly coupled, and when lower-layer communication becomes abnormal, the upper-layer communication is incidentally discarded.
[Summary]

The device server system according to the present invention does not discard the virtual USB device connection as in the prior art even when the communication between the PC and the device server becomes unstable. Furthermore, the device server system according to the present invention uses a plurality of TCP sessions (communication pipes) for virtual USB device connection, so that even if one communication pipe becomes unstable, another communication pipe is used instead. By doing so, communication using the virtual USB device connection can be continued without interruption. As a result, a device server system with high reliability and capable of high-speed processing is obtained.

Conventional device server system Functional blocks in a conventional device server system Communication pipe in device server system PC function block Device server functional block Operation flow

205 Virtual USB device connection management means 401 First communication abnormality detection means 402 First execution prevention means 403 Communication pipe switching means 502 Second communication abnormality detection means 503 Second execution prevention means 504 USB device initialization means

Claims (6)

A communication system between network terminals configured by a plurality of predetermined lower layer communication and a predetermined upper layer communication using one or more of the predetermined lower layer communication,
A communication abnormality detecting means for detecting a communication abnormality of a predetermined lower layer communication used by the upper layer communication;
Upper layer communication discarding means for discarding the upper layer communication;
An execution avoidance means for disabling the upper layer communication discarding means for a predetermined period when the communication abnormality detection means detects an abnormality;
A communication system comprising: The predetermined period is a period until the predetermined lower layer communication in which the communication abnormality detected by the communication abnormality detection means has occurred returns to normal communication.
The communication system according to claim 1. The communication system further comprises:
Communication switching means for switching a predetermined lower layer communication used by the upper layer communication to another lower layer communication in which no abnormality has occurred, when the communication abnormality detection unit detects an abnormality,
The predetermined period is a period until the communication switching by the communication switching unit is completed.
The communication system according to claim 1. A peripheral device server system in which a peripheral device connected to a peripheral device and a client of the peripheral device server are connected to a network,
A virtual peripheral connection that is a virtual connection between the client and the peripheral;
Communication abnormality detection means for detecting an abnormality in communication between the client and the peripheral device server;
Virtual peripheral device connection discarding means for discarding the virtual peripheral device connection;
An execution avoidance means for disabling the virtual peripheral device connection discarding means for a predetermined period when the communication abnormality detection means detects an abnormality;
A peripheral device server system comprising: The peripheral device server system further includes:
Peripheral device initialization means for initializing the internal state of the peripheral device,
Targets that the execution avoiding means prevent execution include the peripheral device initialization means in addition to the virtual peripheral device connection discarding means,
The peripheral device server system according to claim 4. A peripheral device server system in which a peripheral device connected to a peripheral device and a client of the peripheral device server are connected to a network,
A plurality of communication pipes for performing communication between the client and the peripheral device server using different addresses;
A virtual peripheral connection that is a virtual connection between the client and the peripheral using any one of the plurality of communication pipes;
Communication abnormality detection means for detecting an abnormality in communication between the client and the peripheral device server;
Virtual peripheral device connection discarding means for discarding the virtual peripheral device connection;
An execution avoidance means for disabling the virtual peripheral device connection discarding means when the communication abnormality detection means detects an abnormality;
A communication pipe switching means for switching the communication pipe used by the virtual peripheral device connection to another communication pipe having better communication quality than the currently used communication pipe when the communication abnormality detection means detects an abnormality;
A peripheral device server system comprising: