(Delphi ActiveX) 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 for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
scard: TChilkatSCard;
success: Integer;
json: TChilkatJsonObject;
name: WideString;
sbState: TChilkatStringBuilder;
i: Integer;
count_i: Integer;
stReaders: TChilkatStringTable;
numReaders: Integer;
json2: TChilkatJsonObject;
changed: Integer;
state: WideString;
atr: WideString;
numChanged: Integer;

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

scard := TChilkatSCard.Create(Self);

// First establish a context to the PC/SC Resource Manager
success := scard.EstablishContext('user');
if (success = 0) then
  begin
    Memo1.Lines.Add(scard.LastErrorText);
    Exit;
  end;

// 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.
json := TChilkatJsonObject.Create(Self);
success := scard.FindSmartcards(json.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(scard.LastErrorText);
    Exit;
  end;

// 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 := 0;
Memo1.Lines.Add(json.Emit());
Memo1.Lines.Add(' ');

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

sbState := TChilkatStringBuilder.Create(Self);

i := 0;
count_i := json.SizeOfArray('reader');
while i < count_i do
  begin
    json.I := i;
    name := json.StringOf('reader[i].name');

    sbState.Clear();
    json.StringOfSb('reader[i].state',sbState.ControlInterface);

    if (sbState.Contains('present',1) = 1) then
      begin
        Memo1.Lines.Add(name + ' has a smart card inserted.');
      end
    else
      begin
        Memo1.Lines.Add(name + ' does not have a smart card inserted.');
      end;
    i := i + 1;
  end;

Memo1.Lines.Add(' ');

// 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.
stReaders := TChilkatStringTable.Create(Self);
success := scard.ListReaders(stReaders.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(scard.LastErrorText);
    Exit;
  end;

// Show the reader names..
numReaders := stReaders.Count;
i := 0;
while i < numReaders do
  begin
    Memo1.Lines.Add(IntToStr(i) + ': ' + stReaders.StringAt(i));
    i := i + 1;
  end;

// 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.
json2 := TChilkatJsonObject.Create(Self);
success := scard.GetStatusChange(30000,stReaders.ControlInterface,json2.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(scard.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add(' ');

// Let's see what happened...
json2.EmitCompact := 0;
Memo1.Lines.Add(json2.Emit());
Memo1.Lines.Add(' ');

// 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...

numChanged := json2.IntOf('numChanged');
Memo1.Lines.Add('number of readers with a changed state: ' + IntToStr(numChanged));

i := 0;
count_i := json2.SizeOfArray('reader');
while i < count_i do
  begin
    json2.I := i;
    changed := json2.BoolOf('reader[i].changed');
    if (changed = 1) then
      begin
        name := json2.StringOf('reader[i].name');
        state := json2.StringOf('reader[i].state');

        Memo1.Lines.Add('Changed: ');
        Memo1.Lines.Add('    reader name: ' + name);
        Memo1.Lines.Add('    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') = 1) then
          begin
            atr := json2.StringOf('reader[i].atr');
            Memo1.Lines.Add('    ATR of card inserted into this reader: ' + atr);
          end;
      end;
    i := i + 1;
  end;

// 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 = 0) then
  begin
    Memo1.Lines.Add(scard.LastErrorText);
  end;
end;