Visual FoxPro

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

See more SCard Examples

Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

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

Visual FoxPro

LOCAL lnSuccess
LOCAL loScard
LOCAL loJson
LOCAL lcName
LOCAL loSbState
LOCAL i
LOCAL lnCount_i
LOCAL loStReaders
LOCAL lnNumReaders
LOCAL loJson2
LOCAL lnChanged
LOCAL lcState
LOCAL lcAtr
LOCAL lnNumChanged

lnSuccess = 0

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

loScard = CreateObject('Chilkat.SCard')

*  First establish a context to the PC/SC Resource Manager
lnSuccess = loScard.EstablishContext("user")
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    CANCEL
ENDIF

*  First we'll examine the state of all connected readers to see which have smartcards already inserted..
*  Get JSON containing information about the smartcards currently inserted into readers.
*  This also includes information about USB security tokens.
loJson = CreateObject('Chilkat.JsonObject')
lnSuccess = loScard.FindSmartcards(loJson)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    CANCEL
ENDIF

*  When writing this example, I have 3 smart card readers plugged into my system.
*  One of them has a smart card inserted.
*  Here's the JSON returned by FindSmartcards...

*  {
*    "reader": [
*      {
*        "name": "Alcor Micro USB Smart Card Reader 0",
*        "state": "empty"
*      },
*      {
*        "name": "Generic Smart Card Reader Interface 0",
*        "state": "present",
*        "vendorName": "Generic",
*        "serialNumber": "3230303730383138303030303030303030",
*        "systemName": "Generic Smart Card Reader Interface 0",
*        "card": {
*          "atr": "3BFC180000813180459067464A00641606F2727E00E0",
*          "windows": {
*            "miniDriver": "tagliov70px.dll",
*            "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
*            "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
*          }
*        }
*      },
*      {
*        "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
*        "state": "empty"
*      }
*    ]
*  }

loJson.EmitCompact = 0
? loJson.Emit()
? " "

*  We can iterate over the JSON to find the readers with a smart card already inserted..

loSbState = CreateObject('Chilkat.StringBuilder')

i = 0
lnCount_i = loJson.SizeOfArray("reader")
DO WHILE i < lnCount_i
    loJson.I = i
    lcName = loJson.StringOf("reader[i].name")

    loSbState.Clear()
    loJson.StringOfSb("reader[i].state",loSbState)

    IF (loSbState.Contains("present",1) = 1) THEN
        ? lcName + " has a smart card inserted."
    ELSE
        ? lcName + " does not have a smart card inserted."
    ENDIF

    i = i + 1
ENDDO
? " "

*  Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

*  Get the list of all readers.
loStReaders = CreateObject('Chilkat.StringTable')
lnSuccess = loScard.ListReaders(loStReaders)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    RELEASE loSbState
    RELEASE loStReaders
    CANCEL
ENDIF

*  Show the reader names..
lnNumReaders = loStReaders.Count
i = 0
DO WHILE i < lnNumReaders
    ? STR(i) + ": " + loStReaders.StringAt(i)
    i = i + 1
ENDDO

*  Sample output from the above loop.
*  0: Alcor Micro USB Smart Card Reader 0
*  1: Generic Smart Card Reader Interface 0
*  2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
*  

*  Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
loJson2 = CreateObject('Chilkat.JsonObject')
lnSuccess = loScard.GetStatusChange(30000,loStReaders,loJson2)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    RELEASE loSbState
    RELEASE loStReaders
    RELEASE loJson2
    CANCEL
ENDIF

? " "

*  Let's see what happened...
loJson2.EmitCompact = 0
? loJson2.Emit()
? " "

*  This is what json2 contains.
*  A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
*  The "numChanged" indicates that one reader's status changed.  
*  The "changed":true indicates the reader that changed.   The state is now "present".

*  {
*    "numChanged": 1,
*    "reader": [
*      {
*        "name": "Alcor Micro USB Smart Card Reader 0",
*        "changed": false,
*        "state": "empty"
*      },
*      {
*        "name": "Generic Smart Card Reader Interface 0",
*        "changed": false,
*        "state": "present",
*        "atr": "3BFC180000813180459067464A00641606F2727E00E0"
*      },
*      {
*        "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
*        "changed": true,
*        "state": "present",
*        "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
*      }
*    ]
*  }

*  Find the reader that changed...

lnNumChanged = loJson2.IntOf("numChanged")
? "number of readers with a changed state: " + STR(lnNumChanged)

i = 0
lnCount_i = loJson2.SizeOfArray("reader")
DO WHILE i < lnCount_i
    loJson2.I = i
    lnChanged = loJson2.BoolOf("reader[i].changed")
    IF (lnChanged = 1) THEN
        lcName = loJson2.StringOf("reader[i].name")
        lcState = loJson2.StringOf("reader[i].state")

        ? "Changed: "
        ? "    reader name: " + lcName
        ? "    new state: " + lcState

        *  If a card is now in this reader, we should have the ATR of the card..
        IF (loJson2.HasMember("reader[i].atr") = 1) THEN
            lcAtr = loJson2.StringOf("reader[i].atr")
            ? "    ATR of card inserted into this reader: " + lcAtr
        ENDIF

    ENDIF

    i = i + 1
ENDDO

*  The output from the above loop:

*  number of readers with a changed state: 1
*  Changed: 
*      reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
*      new state: present
*      ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

*  Applications should always release the context when finished.
lnSuccess = loScard.ReleaseContext()
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
ENDIF

RELEASE loScard
RELEASE loJson
RELEASE loSbState
RELEASE loStReaders
RELEASE loJson2