DataFlex

PC/SC Async Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

See more SCard Examples

Demonstrates how to start an asynchronous Chilkat task to wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader. After starting the background task, the code loops to check on the status of your task.

Note: Instead of writing a loop to wait for the status change, your application might periodically check the task status via a timer event or something similar. The purpose of this example is to show (1) how to start the async task, and (2) how to periodically check the status of the task.

Note: This functionality was introduced in Chilkat v9.5.0.87.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoScard
    Variant vStReaders
    Handle hoStReaders
    Variant vJson
    Handle hoJson
    Variant vTask
    Handle hoTask
    String sTemp1
    Boolean bTemp1

    Move False To iSuccess

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    Get Create (RefClass(cComChilkatSCard)) To hoScard
    If (Not(IsComObjectCreated(hoScard))) Begin
        Send CreateComObject of hoScard
    End

    // First establish a context to the PC/SC Resource Manager
    Get ComEstablishContext Of hoScard "user" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoScard To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Get the list of all readers.
    Get Create (RefClass(cComChilkatStringTable)) To hoStReaders
    If (Not(IsComObjectCreated(hoStReaders))) Begin
        Send CreateComObject of hoStReaders
    End
    Get pvComObject of hoStReaders to vStReaders
    Get ComListReaders Of hoScard vStReaders To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoScard To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Create a Chilkat task to wait for a max of 1 hour (3600 seconds, or 3600000 milliseconds) for any smart card reader status change.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Get pvComObject of hoStReaders to vStReaders
    Get pvComObject of hoJson to vJson
    Get ComGetStatusChangeAsync Of hoScard 3600000 vStReaders vJson To vTask
    If (IsComObject(vTask)) Begin
        Get Create (RefClass(cComChilkatTask)) To hoTask
        Set pvComObject Of hoTask To vTask
    End
    Get ComLastMethodSuccess Of hoScard To bTemp1
    If (bTemp1 = False) Begin
        Get ComLastErrorText Of hoScard To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Start the task in a background thread.
    Get ComRun Of hoTask To iSuccess
    If (Not iSuccess) Begin
        Get ComLastErrorText Of hoTask To sTemp1
        Showln sTemp1
    End

    // Loop until the task is finished, which happens when any reader's status changes.
    // Instead of looping here, your application could periodically check on the task status in some other way,
    // such as in a periodic timer event..
    While ((ComFinished(hoTask)) <> True)

        // Sleep 100 ms.  
        Send ComSleepMs To hoTask 100
    Loop

    // When we call GetStatusChangeAsync, what's really happening is that GetStatusChange is being called in a background thread.
    // It returns a boolean (success/failure).  Therefore, we call task.GetResultBool to get the boolean returned by GetStatusChange
    // in the background thread.
    Get ComGetResultBool Of hoTask To iSuccess
    If (iSuccess = False) Begin
        // The call to GetStatusChange in the background thread failed.  Let's find out why by getting the LastErrorText
        // for the background synchronous call.
        Get ComResultErrorText Of hoTask To sTemp1
        Showln sTemp1
    End

    Send Destroy of hoTask

    // If the background call to GetStatusChange succeeded, then the result was placed in the last arg,
    // which was our variable named "json".
    If (iSuccess = False) Begin
        Procedure_Return
    End

    // Let's see what happened...
    Set ComEmitCompact Of hoJson To False
    Get ComEmit Of hoJson To sTemp1
    Showln sTemp1
    Showln " "

    // See the Wait for Smart Card Insertion/Removal Example for details about parsing the returned JSON.

    // Applications should always release the context when finished.
    Get ComReleaseContext Of hoScard To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoScard To sTemp1
        Showln sTemp1
    End

    // Note: It may be necessary to call FinalizeThreadPool in some programming environments just before your program exits.
    // (Not after every async function call, but only before program exit.)
    // See Call FinalizeThreadPool before program exit


End_Procedure