Xbase++

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.

Xbase++

LOCAL nSuccess
LOCAL oScard
LOCAL oJson
LOCAL cName
LOCAL oSbState
LOCAL i
LOCAL nCount_i
LOCAL oStReaders
LOCAL nNumReaders
LOCAL oJson2
LOCAL nChanged
LOCAL cState
LOCAL cAtr
LOCAL nNumChanged

nSuccess := 0

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

oScard := CreateObject("Chilkat.SCard")

//  First establish a context to the PC/SC Resource Manager
nSuccess := oScard:EstablishContext("user")
IF (nSuccess == 0)
    ? oScard:LastErrorText
    oScard:destroy()
    RETURN
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.
oJson := CreateObject("Chilkat.JsonObject")
nSuccess := oScard:FindSmartcards(oJson)
IF (nSuccess == 0)
    ? oScard:LastErrorText
    oScard:destroy()
    oJson:destroy()
    RETURN
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"
//      }
//    ]
//  }

oJson:EmitCompact := 0
? oJson:Emit()
? " "

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

oSbState := CreateObject("Chilkat.StringBuilder")

i := 0
nCount_i := oJson:SizeOfArray("reader")
DO WHILE i < nCount_i
    oJson:I := i
    cName := oJson:StringOf("reader[i].name")

    oSbState:Clear()
    oJson:StringOfSb("reader[i].state", oSbState)

    IF (oSbState:Contains("present", 1) == 1)
        ? cName + " has a smart card inserted."
    ELSE
        ? cName + " 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.
oStReaders := CreateObject("Chilkat.StringTable")
nSuccess := oScard:ListReaders(oStReaders)
IF (nSuccess == 0)
    ? oScard:LastErrorText
    oScard:destroy()
    oJson:destroy()
    oSbState:destroy()
    oStReaders:destroy()
    RETURN
ENDIF

//  Show the reader names..
nNumReaders := oStReaders:Count
i := 0
DO WHILE i < nNumReaders
    ? Str(i) + ": " + oStReaders: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.
oJson2 := CreateObject("Chilkat.JsonObject")
nSuccess := oScard:GetStatusChange(30000, oStReaders, oJson2)
IF (nSuccess == 0)
    ? oScard:LastErrorText
    oScard:destroy()
    oJson:destroy()
    oSbState:destroy()
    oStReaders:destroy()
    oJson2:destroy()
    RETURN
ENDIF

? " "

//  Let's see what happened...
oJson2:EmitCompact := 0
? oJson2: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...

nNumChanged := oJson2:IntOf("numChanged")
? "number of readers with a changed state: " + Str(nNumChanged)

i := 0
nCount_i := oJson2:SizeOfArray("reader")
DO WHILE i < nCount_i
    oJson2:I := i
    nChanged := oJson2:BoolOf("reader[i].changed")
    IF (nChanged == 1)
        cName := oJson2:StringOf("reader[i].name")
        cState := oJson2:StringOf("reader[i].state")

        ? "Changed: "
        ? "    reader name: " + cName
        ? "    new state: " + cState

        //  If a card is now in this reader, we should have the ATR of the card..
        IF (oJson2:HasMember("reader[i].atr") == 1)
            cAtr := oJson2:StringOf("reader[i].atr")
            ? "    ATR of card inserted into this reader: " + cAtr
        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.
nSuccess := oScard:ReleaseContext()
IF (nSuccess == 0)
    ? oScard:LastErrorText
ENDIF

oScard:destroy()
oJson:destroy()
oSbState:destroy()
oStReaders:destroy()
oJson2:destroy()