Windows: card-inserted/card-removed events fire inconsistently

[siriwatknp]

Environment

• OS: Windows 11
• Node.js: 22.x (via Electron 35)
• smartcard version: 3.7.0

Problem

On Windows, card-inserted and card-removed events fire inconsistently. The same code works reliably on macOS.

Observed behavior:

• reader-attached fires reliably
• card-inserted fires sometimes but not always when inserting a card
• card-removed rarely fires when removing a card
• If card is already in reader when reader-attached fires, hasCard: true is detected and card-inserted fires (this works)

Reproduction

const { Devices } = require('smartcard');

const devices = new Devices();

devices.on('reader-attached', (reader) => {
  console.log('reader-attached', reader.name, 'hasCard:', (reader.state & 0x20) !== 0);
});

devices.on('card-inserted', ({ reader }) => {
  console.log('card-inserted', reader.name);
});

devices.on('card-removed', ({ reader }) => {
  console.log('card-removed', reader.name);
});

devices.start();

Steps:

1. Run script on Windows 11
2. Plug in USB card reader → reader-attached fires ✓
3. Insert card → card-inserted sometimes fires, sometimes doesn't
4. Remove card → card-removed rarely fires

Suspected cause

Looking at reader_monitor.cpp, the issue appears to be in how SCardGetStatusChange() state tracking works on Windows:

// State stored without SCARD_STATE_CHANGED flag
readers_[i].lastState = newState & ~SCARD_STATE_CHANGED;

// Next iteration uses this as dwCurrentState
state.dwCurrentState = reader.lastState;

If lastState gets out of sync with actual reader state (timing issue specific to Windows PC/SC), subsequent state changes aren't detected.

Workaround

Periodically stopping and restarting the monitor resets state tracking and improves reliability:

setInterval(() => {
  devices.stop();
  devices = new Devices();
  // re-attach event listeners...
  devices.start();
}, 5000);

This suggests the native state tracking diverges from actual hardware state over time on Windows.

Additional context

• Windows Smart Card service is running
• Tested with ACR38U reader
• Thai National ID card (contact-based, T=0 protocol)

[siriwatknp]

Note that on MacOS, it works perfectly fine.
This issue happens on Windows only

[tomkp]

Fixed in PR #112.

Root causes addressed:

1. Reader state was tracked using array indices which became invalid when readers were added/removed (PnP events) - now uses map keyed by reader name
2. Windows PC/SC may not always set SCARD_STATE_CHANGED correctly - added state validation on timeout
3. State tracking could drift out of sync over time - added periodic full state refresh every ~10 seconds

Can you please test with your reader on Windows 11 and confirm the card-inserted/card-removed events now fire reliably?

Let me know if you have any problems. Thanks Tom

[siriwatknp]

@tomkp The issue still present after updated to 3.7.1