Examples

Introduction

This page presents some examples to help developers which use libnfc.

Simple tag UID reader.

This short commented code example should be helpful to quick start development with libnfc, it grab the first available NFC device and print the first found ISO14443-A tag (e.g. MIFARE Classic, MIFARE Ultralight).

// To compile this simple example:
// $ gcc -o quick_start_example1 quick_start_example1.c -lnfc

#include <stdlib.h>
#include <nfc/nfc.h>

static void
print_hex(const uint8_t *pbtData, const size_t szBytes)
{
  size_t  szPos;

  for (szPos = 0; szPos < szBytes; szPos++) {
    printf("%02x  ", pbtData[szPos]);
  }
  printf("\n");
}

int
main(int argc, const char *argv[])
{
  nfc_device *pnd;
  nfc_target nt;

  // Allocate only a pointer to nfc_context
  nfc_context *context;

  // Initialize libnfc and set the nfc_context
  nfc_init(&context);
  if (context == NULL) {
    printf("Unable to init libnfc (malloc)\n");
    exit(EXIT_FAILURE);
  }

  // Display libnfc version
  const char *acLibnfcVersion = nfc_version();
  (void)argc;
  printf("%s uses libnfc %s\n", argv[0], acLibnfcVersion);

  // Open, using the first available NFC device which can be in order of selection:
  //   - default device specified using environment variable or
  //   - first specified device in libnfc.conf (/etc/nfc) or
  //   - first specified device in device-configuration directory (/etc/nfc/devices.d) or
  //   - first auto-detected (if feature is not disabled in libnfc.conf) device
  pnd = nfc_open(context, NULL);

  if (pnd == NULL) {
    printf("ERROR: %s\n", "Unable to open NFC device.");
    exit(EXIT_FAILURE);
  }
  // Set opened NFC device to initiator mode
  if (nfc_initiator_init(pnd) < 0) {
    nfc_perror(pnd, "nfc_initiator_init");
    exit(EXIT_FAILURE);
  }

  printf("NFC reader: %s opened\n", nfc_device_get_name(pnd));

  // Poll for a ISO14443A (MIFARE) tag
  const nfc_modulation nmMifare = {
    .nmt = NMT_ISO14443A,
    .nbr = NBR_106,
  };
  if (nfc_initiator_select_passive_target(pnd, nmMifare, NULL, 0, &nt) > 0) {
    printf("The following (NFC) ISO14443A tag was found:\n");
    printf("    ATQA (SENS_RES): ");
    print_hex(nt.nti.nai.abtAtqa, 2);
    printf("       UID (NFCID%c): ", (nt.nti.nai.abtUid[0] == 0x08 ? '3' : '1'));
    print_hex(nt.nti.nai.abtUid, nt.nti.nai.szUidLen);
    printf("      SAK (SEL_RES): ");
    print_hex(&nt.nti.nai.btSak, 1);
    if (nt.nti.nai.szAtsLen) {
      printf("          ATS (ATR): ");
      print_hex(nt.nti.nai.abtAts, nt.nti.nai.szAtsLen);
    }
  }
  // Close NFC device
  nfc_close(pnd);
  // Release the context
  nfc_exit(context);
  exit(EXIT_SUCCESS);
}