(Xojo Plugin) 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.

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

Dim scard As New Chilkat.SCard

// First establish a context to the PC/SC Resource Manager
Dim success As Boolean
success = scard.EstablishContext("user")
If (success = False) Then
    System.DebugLog(scard.LastErrorText)
    Return
End If

// 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.
Dim json As New Chilkat.JsonObject
success = scard.FindSmartcards(json)
If (success = False) Then
    System.DebugLog(scard.LastErrorText)
    Return
End If

// 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"
//     }
//   ]
// }

json.EmitCompact = False
System.DebugLog(json.Emit())
System.DebugLog(" ")

// We can iterate over the JSON to find the readers with a smart card already inserted..
Dim name As String
Dim sbState As New Chilkat.StringBuilder

Dim i As Int32
i = 0
Dim count_i As Int32
count_i = json.SizeOfArray("reader")
While i < count_i
    json.I = i
    name = json.StringOf("reader[i].name")

    sbState.Clear 
    success = json.StringOfSb("reader[i].state",sbState)

    If (sbState.Contains("present",True) = True) Then
        System.DebugLog(name + " has a smart card inserted.")
    Else
        System.DebugLog(name + " does not have a smart card inserted.")
    End If

    i = i + 1
Wend
System.DebugLog(" ")

// 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.
Dim stReaders As New Chilkat.StringTable
success = scard.ListReaders(stReaders)
If (success = False) Then
    System.DebugLog(scard.LastErrorText)
    Return
End If

// Show the reader names..
Dim numReaders As Int32
numReaders = stReaders.Count
i = 0
While i < numReaders
    System.DebugLog(Str(i) + ": " + stReaders.StringAt(i))
    i = i + 1
Wend

// 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.
Dim json2 As New Chilkat.JsonObject
success = scard.GetStatusChange(30000,stReaders,json2)
If (success = False) Then
    System.DebugLog(scard.LastErrorText)
    Return
End If

System.DebugLog(" ")

// Let's see what happened...
json2.EmitCompact = False
System.DebugLog(json2.Emit())
System.DebugLog(" ")

// 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...
Dim changed As Boolean
Dim state As String
Dim atr As String

Dim numChanged As Int32
numChanged = json2.IntOf("numChanged")
System.DebugLog("number of readers with a changed state: " + Str(numChanged))

i = 0
count_i = json2.SizeOfArray("reader")
While i < count_i
    json2.I = i
    changed = json2.BoolOf("reader[i].changed")
    If (changed = True) Then
        name = json2.StringOf("reader[i].name")
        state = json2.StringOf("reader[i].state")

        System.DebugLog("Changed: ")
        System.DebugLog("    reader name: " + name)
        System.DebugLog("    new state: " + state)

        // If a card is now in this reader, we should have the ATR of the card..
        If (json2.HasMember("reader[i].atr") = True) Then
            atr = json2.StringOf("reader[i].atr")
            System.DebugLog("    ATR of card inserted into this reader: " + atr)
        End If

    End If

    i = i + 1
Wend

// 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.
success = scard.ReleaseContext()
If (success = False) Then
    System.DebugLog(scard.LastErrorText)
End If