Abstract:
In a communication environment in which multiple virtual port drivers use a single communication port, a communication control method enables a first virtual port driver and a second virtual port driver that is occupying the communication port to communicate through the same communication port. The communication control method includes executing a communication process in which the first virtual port driver emulates a specific communication port in communication with a first device driver to which the first virtual port driver corresponds. At least when the second virtual port driver occupies the communication port, the communication control method executes a communication process in which the first virtual port driver emulates, for the second virtual port driver, the second device driver to which the second virtual port driver corresponds.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    Japanese Patent application No. 2009-169166 is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a communication control method and a control program, and relates more particularly to a communication control method and a control program that enable an application program that is compatible with a specific communication interface to connect to another communication interface that is different from the specific communication interface. 
         [0004]    2. Description of Related Art 
         [0005]    In order to use various peripheral devices that are accessible through the operating system, application programs typically incorporate various device drivers, which are software modules for controlling particular peripheral devices. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2008-158785.More specifically, a device driver is software for handling input and output between an application program and a particular device, and for controlling input/output devices (hardware such as expansion cards and peripheral devices) such as graphic display devices, printers, and Ethernet® boards. 
         [0006]    Configurations and methods that communicate with a physical communication port through a virtual port driver that primarily handles control of the communication protocol are also used in order to efficiently produce and use device drivers. In a communication environment having multiple virtual port drivers that all use the same physical communication port, competition occurs amongst at least some of the virtual port drivers for use of the same communication port at the same time or during the same time frame. 
         [0007]    Depending upon the type or design of the virtual port driver, the virtual port driver may also continue to occupy the communication port to which it is connected once it secures a connection to the communication port. An example of this type of virtual port driver is, more specifically, a virtual port driver that constantly checks the connection status once communication is established. This type of virtual port driver does not release the communication port because it must constantly determine if the controlled device is connected to the communication port to which the virtual port driver is connected. 
         [0008]    Therefore, if one virtual port driver is thus occupying the communication port and a second virtual port driver attempts to use the same communication port, the second virtual port driver will not be able to use the communication port. This means that a device driver (application program) that connects to the communication port through the second virtual port driver will not be able to use the communication port. 
       SUMMARY OF INVENTION 
       [0009]    In a communication environment in which a plurality of virtual port drivers use a single communication port and there is a virtual port driver occupying the communication port, a communication control method and control program according to the present invention enable a virtual port driver other than the virtual port driver that is occupying the communication port to use the communication port and communicate. 
         [0010]    A first aspect of the invention is a communication control method for a control device that has a plurality of device drivers, including a first and a second device driver, respectively corresponding respectively to a plurality of virtual port drivers, including a first and a second virtual port driver, that use a common communication port, and that communicates with a controlled device through the virtual port drivers and the common communication port. The communication control method comprises executing a first communication process in which the first virtual port driver emulates a specific communication port addressed by the first device driver to which the first virtual port driver corresponds. When at least the second virtual port driver occupies the common communication port, the method further includes executing a second communication process in which the first virtual port driver emulates, for the second virtual port driver, the second device driver to which the second virtual port driver corresponds. 
         [0011]    A communication control method according to another aspect of the invention includes executing a third communication process in which the first virtual port driver has a communication module that corresponds to the second virtual port driver and emulates the second device driver through the communication module. 
         [0012]    In this aspect of the invention the first virtual port driver emulates a specific communication port in communication with the fist device driver to which the first virtual port driver corresponds, and at least when another (second) virtual port driver occupies that communication port, emulates, in communication between the first and second virtual port drivers, the latter occupying the communication port, the second device driver to which the second virtual port driver corresponds. 
         [0013]    The first device driver corresponding to the first virtual port driver, or more particularly the application that uses this device driver to communicate through the common communication port, can communicate through such port without being affected by whether or not another virtual port driver occupies the communication port. 
         [0014]    The communication control method according to another aspect of the invention further preferably includes the first virtual port driver (i) processing a communication request to the common communication port; and executing a fourth communication process that, when a response permitting communication through the common communication port is not received in response to the communication request process, determines that the second virtual port driver occupies the common communication port and emulates the second device driver to which the second virtual port driver corresponds. 
         [0015]    When one virtual port driver asserts a communication request to the common communication port and then does not receive a response permitting communication through such port, this aspect of the invention determines that another virtual port driver is occupying the communication port and therefore goes to a communication process that emulates the specific device driver corresponding to that other virtual port driver. As a result, the application, or more particularly the user, can execute the communication process to communicate with a particular device without knowing whether or not the communication port is occupied. 
         [0016]    Another aspect of the invention entails a computer-readable medium containing a control program for execution by one or more processors for controlling a control device that has a plurality of device drivers, including first and second device drivers, respectively corresponding to a plurality of virtual port drivers, including a first and a second virtual port driver, that use a common communication port, and that communicates with a controlled device through the virtual port drivers and the common communication port. The control program comprises instructions for executing a first communication process in which the first virtual port driver emulates a specific communication port in communication with the first device driver to which the first virtual port driver corresponds; and instructions for executing a second communication process in which the first virtual port driver emulates, for the second virtual port driver, the second device driver to which the second virtual port driver corresponds, when at least the second virtual port driver occupies the common communication port. 
         [0017]    In a control program according to another aspect of the invention, the control program further includes instructions for executing a third communication process in which the first virtual port driver has a communication module that corresponds to the second virtual port driver, and emulates the second device driver through the communication module. 
         [0018]    With this aspect of the invention, the device driver corresponding to the first virtual port driver, or more particularly the application that uses this device driver to communicate through the communication port, can communicate through the communication port without being affected by whether or not another virtual port driver occupies the communication port. 
         [0019]    Another aspect of the invention is embodied in a control device that is configured to communicate with a controlled device by executing communication processes as described above. 
       Effect of the Invention 
       [0020]    In a communication environment in which there is a plurality of virtual port drivers that use a single communication port and there is a virtual port driver occupying the communication port, the communication control method and control program of the invention enable a virtual port driver other than another virtual port driver that is occupying the communication port to communicate through the occupied communication port. 
         [0021]    Therefore, when a plurality of virtual port drivers use a same communication port, the application program can communicate through the same communication port regardless of which device driver using any of the virtual port drivers is used. 
         [0022]    Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a block diagram showing the configuration of a POS system according to a preferred embodiment of the invention. 
           [0024]      FIG. 2  is a block diagram showing the configuration of a POS terminal device. 
           [0025]      FIG. 3  is a functional block diagram of the communication control system of the POS terminal device in accordance with embodiments of the invention. 
           [0026]      FIG. 4  illustrates the configuration of the device driver DD 1  and virtual port driver VPD 1  in detail, according to embodiments of the invention. 
           [0027]      FIG. 5  illustrates the configuration of a virtual port driver VPD 2  in accordance with embodiments of the invention. 
           [0028]      FIG. 6  is a sequence flow chart of the printing process, according to a preferred embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    A preferred embodiment of the present invention is described below with reference to the accompanying figures. 
         [0030]      FIG. 1  is a block diagram showing the configuration of a POS system according to a preferred embodiment of the invention. The POS system  10  is a sales management system typically used in retail stores such as supermarkets. A POS system  10  generally has a plurality of POS terminals  12  each with a printer  11  connected thereto for printing receipts or coupons, for example, and a POS server  14  connected to the plural POS terminals  12  over the Internet or other communication network  13 . The POS server  14  administers the plural POS terminals  12  and manages data such as sales data collected from the POS terminals  12 . 
         [0031]    Note that in this embodiment of the invention the printers  11  function as controlled devices, and the POS terminals  12  function as control devices that control the controlled devices. 
         [0032]      FIG. 2  is a schematic block diagram of a POS terminal  12 . The POS terminal  12  has a keyboard  21 , barcode reader  22 , card reader  23 , main terminal  24 , and a display  25 . 
         [0033]    The keyboard  21  is used by the operator to manually input product information such as the price, product code, and discount rate, customer information such as age and sex, or other information. 
         [0034]    The barcode reader  22  is used to read the barcode affixed to each product and thereby input product information. The card reader  23  is used to read customer credit cards or membership cards, for example, and to capture information needed to process credit card transactions and customer information such as membership number. 
         [0035]    The main terminal  24  generates information for printing receipts and coupons based on product data sent from the POS server  14  and information input from the keyboard  21 , barcode reader  22 , or card reader  23 , and outputs the print data to the printer  11 . The display  25  displays product information generated based on the product data sent from the POS server  14 , and displays the product name and price information, for example, for the customer. 
         [0036]    In this embodiment of the invention, the main terminal  24  is rendered by a computer having, for example, a MPU, ROM, and RAM (not shown), and controls operation based on a control program stored in ROM. 
         [0037]    The printer  11  and POS terminal  12  are connected through connectors Cl and C 2  and a communication cable CA, as shown in  FIG. 3 . 
         [0038]    The POS server  14  is rendered by a computer having an MPU, ROM, RAM, hard disk drive storing a database, and other components not shown. 
         [0039]      FIG. 3  is a functional block diagram of the communication control system of the POS terminal  12 . 
         [0040]    An application program AP (such as a POS terminal control program) that runs under the operating system (OS) OPS of the POS terminal  12  is designed to accommodate unknown peripheral devices. Thus, the specific type of printer  11  that may be connected as a peripheral device to the POS terminal  12  may be unknown. As a result, when the printer  11  is actually connected, a device driver DD 1  corresponding to the protocol used to control the printer  11  may also be installed. 
         [0041]    However, when the device driver DD 1  has a function for controlling the actual communication port (a physical port such as a LPT port, COM 1 , or USB port), the communication port with which it can communicate is identified uniquely and cannot be easily changed. 
         [0042]    As a result, when the device driver DD 1  is installed to a system that does not have a communication port that is compatible with the device driver DD 1 , a virtual port driver VPD 1  is installed between the device driver DD 1  and the communication port. The virtual port driver VPD 1  then converts the protocol used by the device driver DD 1  to communicate with the communication port to the protocol used by the communication port to which the peripheral device is actually connected. 
         [0043]    In addition, writing and using the device driver is more efficient if the protocol portion corresponding to the communication port is extracted as a virtual port driver because it can be shared between different types of devices and communication ports. In addition, communication between the device driver and the virtual port driver is possible using a simple communication protocol, which can be easily changed. Conversion is also possible if a different communication protocol is set. 
         [0044]    For example, when the communication port used by the device driver DD 1  is the LPT port and the communication port to which the printer  11  is actually connected is communication port COM 1 , the virtual port driver VPD 1  converts the protocol of the LPT port to the protocol compatible with the COM port. More specifically, the virtual port driver VPD 1  emulates the LPT port for the device driver DD 1 , emulates a device driver compatible with communication port COM 1  for communication through the communication port COM 1 , and thereby enables the device driver DD 1  to control the printer  11  through the COM port. 
         [0045]    Emulating the LPT port (communication port) as used herein means handling the input and output of high and low level digital signals so that it appears to the communicating device (device driver DD 1  in the foregoing example) that it is communicating directly with the LPT port. Emulating a device driver similarly means handling the sending and receiving of data (including both commands and data) so that the communicating device (communication port COM 1  in the foregoing example) appears to be actually exchanging data with the device driver. Other emulation operations noted below operate in the same way. 
         [0046]    If a different type of printer or other peripheral device was connected to the communication port before the device driver DD 1  was installed, a device driver DD 2  for that other type of printer or peripheral device may have also been previously installed. 
         [0047]    Because the device driver DD 2  in this configuration controls a specific communication port, the communication port with which it can communicate is fixed and cannot be easily changed. Therefore, in order to convert the protocol of the communication port with which device driver DD 2  communicates to the protocol used by the communication port to which the peripheral device is actually connected, a virtual port driver VPD 2  may be installed between the device driver DD 2  and the communication port. In other words, the virtual port driver VPD 2  emulates the communication port used by the device driver DD 2  for the device driver DD 2 , emulates the device driver that communicates with communication port COM 1  for the communication port COM 1 , and thereby enables the device driver DD 2  to control the printer  11  through communication port COM 1 . 
         [0048]    In this situation the virtual port driver VPD 2  may occupy communication port COM 1 . This can happen, for example, because the virtual port driver VPD 2  must constantly monitor whether or not the controlled device is connected to the communication port. 
         [0049]    When the communication port COM 1  is thus occupied, a virtual port driver VPD 1  that is subsequently installed cannot access communication port COM 1  and therefore cannot communicate through communication port COM 1 . As a result, the device driver DD 1  that uses the virtual port driver VPD 1 , that is, the application program AP, cannot function. 
         [0050]    Therefore, if a virtual port driver VPD 2  that occupies the communication port is already present when another virtual port driver VPD 1  is installed in this embodiment of the invention, this other virtual port driver VPD 1  is configured to operate by communicating with the desired communication port through virtual port driver VPD 2 . 
         [0051]    More specifically, when the virtual port driver VPD 2  converts the protocol compatible with device driver DD 2  to the protocol compatible with the occupied communication port, the virtual port driver VPD 1  operates to convert the protocol of the device driver DD 1  to the protocol of the device driver DD 2 . 
         [0052]    Yet more specifically, virtual port driver VPD 1  emulates the communication port COM 1  for device driver DD 1 , and emulates the device driver DD 2  that is compatible with the communication port COM 1  for virtual port driver VPD 2 . As a result, the device driver DD 1  can control the printer  11  through communication port COM 1 . 
         [0053]    As a result, virtual port driver VPD 1  is apparently identical to device driver DD 2  from the perspective of virtual port driver VPD 2 , and the application program AP can control the printer  11  through the communication port whether or not virtual port driver VPD 2  occupies the communication port. 
         [0054]    The operation of the device driver and the virtual port driver are described in greater detail below. 
         [0055]    The virtual port driver VPD 1  below is configured to communicate through the communication port COM 1  under the control of the driver control module  31  of the device driver DD 1 . 
         [0056]    When the application program AP outputs a communication request, the driver control module  31  of the device driver DD 1  sends a communication request using its own communication protocol to the virtual port driver VPD 1 . 
         [0057]    As a result, the virtual port driver VPD 1  emulates a communication port based on the communication protocol used by the driver control module  31  ( FIG. 4 ) of the device driver DD 1 . 
         [0058]      FIG. 4  describes the configuration of the device driver DD 1  and the virtual port driver VPD 1 . 
         [0059]    The virtual port driver VPD 1  has the following modules as shown in  FIG. 4 . 
         [0000]    1. COM port communication module  41  that can communicate with serial communication ports (COM 1 , COM 2 , and so forth).
 
2. LPT port communication module  42  that can communicate with parallel communication ports LPT (LPT 1 , LPT 2 , and so forth).
 
3. USB port communication module  43  that can communicate with Universal Serial Bus (USB) communication ports USB (USB 1 , USB 2 , and so forth).
 
4. Ethernet® port communication module  44  that can communicate with an Ethernet® port conforming to a wired LAN communication standard.
 
5. Wireless port communication module  45  that can communicate with a wireless communication port conforming to a wireless LAN communication standard.
 
6. Virtual port communication module  46  that emulates the device driver DD 2  used by the virtual port driver VPD 2  for the virtual port driver VPD 2 .
 
         [0060]    Note that because the virtual port driver VPD 1  is configured to communicate through communication port COM 1  with the driver control module of the device driver DD 1 , the virtual port driver VPD 1  should communicate through the COM port communication module  41  as indicated by the dotted line arrow in  FIG. 4 . 
         [0061]    However, because communication port COM 1  is occupied by the virtual port driver VPD 2  as described above, the virtual port driver VPD 1  asserts a communicate request through the virtual port communication module  46  to the virtual port driver VPD 2  as indicated by the solid line arrow in  FIG. 4  to emulate a driver control module (not shown) of the device driver DD 2 . 
         [0062]      FIG. 5  shows the configuration of the virtual port driver VPD 2  in detail. 
         [0063]    As shown in  FIG. 5  the virtual port driver VPD 2  has the following modules. 
         [0000]    1. COM port communication module  51  that can communicate with serial communication ports (COM 1 , COM 2 , and so forth).
 
2. LPT port communication module  52  that can communicate with parallel communication ports LPT (LPT 1 , LPT 2 , and so forth).
 
3. USB port communication module  53  that can communicate with Universal Serial Bus (USB) communication ports USB (USB 1 , USB 2 , and so forth).
 
4. Ethernet® port communication module  54  that can communicate with an Ethernet® port conforming to a wired LAN communication standard.
 
5. Wireless port communication module  55  that can communicate with a wireless communication port conforming to a wireless LAN communication standard.
 
         [0064]    Because the virtual port driver VPD 2  is configured to communicate through the communication port COM 1  with the driver control module (not shown) of the device driver DD 2 , the virtual port driver VPD 2  communicates through the COM port communication module  51  and communication port COM 1  as shown by the solid line arrow in  FIG. 5  so that the device driver DD 1  can communicate with the printer  11 . 
         [0065]    A specific communication control process is described next using by way of example printing by means of a printer connected to a COM port. 
         [0066]      FIG. 6  is a flow chart of the communication sequence in this embodiment of the invention when printing. 
         [0067]    The device driver DD 1  of an application program AP that runs on the POS terminal  12  first converts the start printing request of the application program AP (step S 11 ) to the protocol of the communication port addressed by the application program (such as the LPT port in this example), and relays the start printing request to the virtual port driver VPD 1  (step S 12 ). 
         [0068]    The virtual port driver VPD 1  to which the start printing request was relayed functions identically to the actual device driver DD 2  that corresponds to the virtual port driver VPD 2 . That is, the virtual port driver VPD 1  converts the relayed start printing request to the protocol of the communication port used by the device driver DD 2  (the USB port in this example), and relays the request through the virtual port communication module  46  to the virtual port driver VPD 2  (step S 13 ). Therefore, the virtual port driver VPD 1  emulates the communication port addressed by the device driver DD 1  for the device driver DD 1 , and emulates the device driver DD 2  for the virtual port driver VPD 2 . 
         [0069]    The virtual port driver VPD 2  then converts the relayed start printing request to the communication protocol for communicating through the COM port communication module with the communication port COM 1 , and outputs the result to the communication port COM 1 . As a result, the start printing request is applied to the printer  11  through the communication port COM 1 , connector Cl, communication cable, and connector C 2  (step S 14 ). That is, the virtual port driver VPD 2  emulates communication port COM 1  for virtual port driver VPD 1 , and emulates device driver DD 2  for communication port COM 1 . 
         [0070]    If the printer  11  that received the start printing request can receive print data, it sends a print start acknowledgement to the communication port COM 1  of the POS terminal  12  through connector C 2 , the communication cable, and connector C 1  (step S 15 ). 
         [0071]    The virtual port driver VPD 2  receives the print start acknowledgement through the communication port COM 1 , converts the communication protocol of the communication port COM 1  to the communication protocol of the virtual port driver VPD 1 , and relays the acknowledgement to the virtual port driver VPD 1  (step S 16 ). More specifically, the virtual port driver VPD 2  emulates the device driver DD 2  for the communication port COM 1 , and emulates the communication port COM 1  for the device driver DD 1 . 
         [0072]    As a result, the virtual port driver VPD 1  that received the print start acknowledgement from the communication port COM 1  by means of emulation converts the communication protocol to the communication protocol of the device driver DD 1  and relays the acknowledgement to the device driver DD 1  (step S 17 ). In other words, the virtual port driver VPD 1  emulates the device driver DD 2  for the virtual port driver VPD 2 , and emulates the communication port used by the device driver DD 1  for the device driver DD 1 . 
         [0073]    The device driver DD 1  then converts the received print start acknowledgement to the data format used by the application program AP and relays the acknowledgement to the application program (step S 18 ). 
         [0074]    The application program AP that received the print start acknowledgement from the device driver DD 1  then sends the print data that is required to print, including the printing control commands and the actual print data, to the device driver DD 1  (step S 19 ). 
         [0075]    As a result, the device driver DD 1  converts the print data to the protocol of the communication port (such as the LPT port) addressed by the application program and relays the print data to the virtual port driver VPD 1  (step S 20 ). 
         [0076]    The virtual port driver VPD 1  to which the print data was relayed then converts the relayed print data to the protocol of the communication port addressed by the device driver DD 2  (such as the USB port), and then relays the print data through the virtual port communication module  46  to the virtual port driver VPD 2  (step S 21 ). The virtual port driver VPD 1  thus emulates the communication port used by the device driver DD 1  for the device driver DD 1 , and emulates the device driver DD 2  for the virtual port driver VPD 2 . 
         [0077]    The virtual port driver VPD 2  then converts the relayed print data to the communication protocol of the communication port COM 1  through the COM port communication module, and outputs to the communication port COM 1 . As a result, the print data is relayed to the printer  11  through the communication port COM 1 , connector C 1 , communication cable, and connector C 2  (step S 22 ). The virtual port driver VPD 2  thus emulates the communication port COM 1  for the virtual port driver VPD 1 , and emulates the device driver DD 2  for the communication port COM 1 . 
         [0078]    As a result, the printer  11  interprets the printing control commands and print data contained in the relayed printing data, and executes the printing process (step S 23 ). 
         [0079]    In this embodiment of the invention as described above, when one virtual port driver tries to communicate through a communication port that is occupied by another virtual port driver in a communication environment in which a plurality of virtual port drivers use a single communication port, the one virtual port driver emulates the device driver to which the other virtual port driver corresponds when communicating with the other virtual port driver that is occupying the communication port so that communication with a controlled device connected through that communication port is possible. 
         [0080]    If when a virtual port driver VPD 1  is installed there is another virtual port driver VPD 2  occupying the communication port COM 1 , the foregoing embodiment describes the one virtual port driver VPD 1  as thereafter communicating with the communication port COM 1  through the other virtual port driver VPD 2 . 
         [0081]    Alternatively, however, a configuration in which the virtual port driver VPD 1 , which is one virtual port driver, executes a communication request process through the COM port communication module  41  to access the communication port COM 1  after the virtual port driver VPD 1  is installed is also conceivable. If a response to this communication request process is then not received from the communication port COM 1 , the invention determines that the virtual port driver VPD 2 , which is another virtual port driver, is occupying the communication port COM 1 , and goes to a communication process in which the one virtual port driver VPD 1  emulates the device driver (device driver DD 2  in this embodiment of the invention) to which virtual port driver VPD 2  (the other virtual port driver) corresponds. 
         [0082]    While the foregoing embodiments are described as using communication port COM 1  as the communication port for communication, the invention is not so limited; rather, the invention can also be applied to other types of communication ports, including an LPT port, USB port, Ethernet® port, or wireless port, for example. 
         [0083]    Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those skilled in the art in light of such disclosure. Any such change or modification is intended to be included within the scope of the present invention to the extent such change or modification is embraced by any of the claims of this application.