NFCTagReaderSession host card emulation (HCE) exception

This is my code:

HCE app:

@available(iOS 17.4, *)
func cardSession(accessCode: String) {
    print("Access code: \(accessCode)")
    let ProcessAPDU: (_ capdu: Data) -> Data = { capdu in
        guard let responseAPDU = accessCode.data(using: .utf8) else {
            print("Failed to convert access code to Data")
            return Data()
        }
        return responseAPDU
    }
    
    Task {
        guard NFCReaderSession.readingAvailable,
              CardSession.isSupported,
              await CardSession.isEligible else {
            self.showQRCode()
            return
        }

        self.cancelSession()
        
        do {
            (UIApplication.shared.delegate as? AppDelegate)?.currentCardSession = try await CardSession()
        } catch {
            self.showQRCode()
            return
        }
        
        guard let cardSession = (UIApplication.shared.delegate as? AppDelegate)?.currentCardSession as? CardSession else {
            print("Card session is nil or not of type CardSession")
            self.showQRCode()
            return
        }
        
        for try await event in cardSession.eventStream {
            switch event {
            case .sessionStarted:
                print("Session started")
                cardSession.alertMessage = NSLocalizedString("Communicating with ticket reader.", comment: "")
                if await !cardSession.isEmulationInProgress {
                    try await cardSession.startEmulation()
                }
            case .readerDetected:
                print("Reader detected")
                if await !cardSession.isEmulationInProgress {
                    try await cardSession.startEmulation()
                }
            case .readerDeselected:
                print("Reader deselected")
            case .received(let cardAPDU):
                do {
                    let responseAPDU = ProcessAPDU(cardAPDU.payload)
                    try await cardAPDU.respond(response: responseAPDU)
                    await cardSession.stopEmulation(status: .success)
                    print("Received APDU: \(cardAPDU.payload)")

                } catch {
                    await cardSession.stopEmulation(status: .failure)
                    print("Error processing APDU: \(error.localizedDescription)")

                }
                self.cancelSession()
            case .sessionInvalidated(reason: let reason):
                print("Session invalidated: \(reason)")
                cardSession.alertMessage = NSLocalizedString("Ending communication with ticket reader.", comment: "")
            @unknown default:
                print("Unknown event: \(event)")
                break
            }
        }
    }
}

Reader app:

func startNFCSession() {
    nfcSession = NFCTagReaderSession(pollingOption: [.iso14443], delegate: self, queue: nil)
    nfcSession?.alertMessage = NSLocalizedString("Hold the device close to scan the ticket.", comment: "")
    nfcSession?.begin()
}

func tagReaderSession(_ session: NFCTagReaderSession, didDetect tags: [NFCTag]) {
    
    guard let tag = tags.first else {
        session.invalidate(errorMessage: NSLocalizedString("No tags found", comment: ""))
        return
    }
    
    guard case let .iso7816(iso7816Tag) = tag else {
        session.invalidate(errorMessage: NSLocalizedString("Tag is not ISO7816", comment: ""))
        return
    }
    
    Task { [iso7816Tag] in
        do {
            try await session.connect(to: tag)
            
            do {
                let apdu = NFCISO7816APDU(instructionClass: 0x00,
                                          instructionCode: 0xA4,
                                          p1Parameter: 0x04,
                                          p2Parameter: 0x00,
                                          data: Data([0xF0, 0x01, 0x02, 0x03, 0x04, 0x05]),
                                          expectedResponseLength: -1)

                var (data, sw1, sw2) = try await iso7816Tag.sendCommand(apdu: apdu)
                print("Response: \(data), SW1: \(sw1), SW2: \(sw2)")
                
                // Verificar que la respuesta sea válida
                if sw1 == 0x90 && sw2 == 0x00 {
                    if let accessCode = String(data: data, encoding: .utf8) {
                        print("Access Code: \(accessCode)")
                        self.verifyTicket(self.getSectors(), accessCode)
                        session.invalidate()
                    } else {
                        print("Failed to decode access code")
                        session.invalidate(errorMessage: NSLocalizedString("Failed to decode access code", comment: ""))
                    }
                } else if sw1 == 0x6A && sw2 == 0x82 {
                    session.invalidate(errorMessage: NSLocalizedString("File not found", comment: ""))
                } else if sw1 == 0x6A && sw2 == 0x86 {
                    session.invalidate(errorMessage: NSLocalizedString("Incorrect parameters P1-P2", comment: ""))
                } else {
                    session.invalidate(errorMessage: String(format: NSLocalizedString("Invalid response: %02x%02x", comment: ""), sw1, sw2))
                }
            } catch {
                print("Sending comment error: \(error.localizedDescription)")
                session.invalidate(errorMessage: String(format: NSLocalizedString("Error sending command: %@", comment: ""), error.localizedDescription))
            }
        } catch {
            if let nfcReaderError = error as? NFCReaderError {
                print(nfcReaderError.code)
                print(nfcReaderError.localizedDescription)
                session.invalidate(errorMessage: String(format: NSLocalizedString(nfcReaderError.localizedDescription, comment: "")))
            } else {
                print(error.localizedDescription)
                session.invalidate(errorMessage: String(format: NSLocalizedString("Connection error: %@", comment: ""), error.localizedDescription))
            }
        }
    }

}

We would like to see a bug report about this including some diagnostic logs to understand what exactly might be going on.

Don't forget to include as much information as you can about the cases you see this problem with. And if you are able to, create a debug level sysdiagnose after reproducing the issue.

To do so, please go to https://developer.apple.com/bug-reporting/profiles-and-logs/ and follow the instructions for Wallet for iOS to install a logging profile on your device. Then, once the logging profile is installed:

• reproduce the problem, and include details about the conditions at the time
• Once the problem is reproduced, follow the instructions at the above link to trigger a sysdiagnose and attach it to the bug report
• make sure you include your app's Bundle ID, any crash reports you have, and any other information you find relevant.

If you have a small sample project that shows your use of HCE and Reader modes, that would be helpful as well.

To file a bug report, you can use the Feedback Assistant.

Once you open the bug report, please post the FB number here for my reference.

If you have any questions about filing a bug report, take a look at Bug Reporting: How and Why?

Argun Tekant /  DTS Engineer / Core Technologies