Sharing through NFC

The basic tasks involved in sharing content through Near Field Communication (NFC) are to ensure that the device supports NFC, initialize the NFC feature, and exchange NDEF messages through the NFC P2P connection. The following sections provide you with the fundamental building blocks for sharing data with other devices.

Initializing NFC

NFC is an international standard (ISO/IEC 18092) that specifies an interface and a protocol for simple wireless interconnection of closely coupled devices.

To initialize NFC:

  1. To use the functions and data types of the NFC API (in mobile and wearable applications), include the <nfc.h> header file in your application:

    #include <nfc.h>
  2. Add the privilege to the application manifest file.
  3. Check whether the device supports NFC by calling the nfc_manager_is_supported() function. It takes no parameters and returns true if NFC is supported on the device.
        gmainloop = g_main_loop_new(NULL, FALSE);
        bool is_nfc_supported = nfc_manager_is_supported();
        if (!is_nfc_supported)
            dlog_print(DLOG_INFO, LOG_TAG, "is_nfc_supported NOT SUPPORTED");

    The gmainloop created above is used to wait for the results of calling asynchronous functions.

  4. Call the nfc_manager_initialize() function to start the initialization:
    int error_code = NFC_ERROR_NONE;
    error_code = nfc_manager_initialize();
    if (error_code != NFC_ERROR_NONE) 
        /* Error handling */
    g_timeout_add(1000, timeout_func, gmainloop);

    Run gmainloop to wait for the initialization result. It is closed when the time set in the g_timeout_add() function elapses. The time is defined in milliseconds, so in the above example the timeout_func is called after 1 second.

Sending and Receiving Messages through NFC P2P

The NFC Data Exchange Format (NDEF) is a packet message format used in the reader/writer and peer-to-peer (P2P) modes. In the following example, the NDEF message contains a business card of the device owner (name, phone number, and email address).

To exchange a simple NDEF message through NFC P2P connection:

  1. Prepare the NDEF message:

    1. To create an NDEF message consisting of text records, use the nfc_ndef_record_create_text() function. The following example creates 3 records for a name, phone number, and email address:

      nfc_ndef_record_h ndef_name_record = NULL;
      nfc_ndef_record_h ndef_phone_record = NULL;
      nfc_ndef_record_h ndef_email_record = NULL;
      const char *name = "John Doe";
      const char *phone = "+82556666888";
      const char *email = "";
      nfc_ndef_record_create_text(&ndef_name_record, name, "en-US", NFC_ENCODE_UTF_8);
      nfc_ndef_record_create_text(&ndef_phone_record, phone, "en-US", NFC_ENCODE_UTF_8);
      nfc_ndef_record_create_text(&ndef_email_record, email, "en-US", NFC_ENCODE_UTF_8);
    2. Create an NDEF message and append the records to the message:

      nfc_ndef_message_h ndef_message = NULL;
      nfc_ndef_message_append_record(ndef_message, ndef_name_record);
      nfc_ndef_message_append_record(ndef_message, ndef_phone_record);
      nfc_ndef_message_append_record(ndef_message, ndef_email_record);
  2. Register callbacks to receive notifications about discovered P2P targets and the received data:
    • To exchange messages using P2P, register a callback for receiving notifications about discovered P2P targets. When the P2P target is discovered, the callback provides a handle to that device and information on whether it is attached or detached.
    • Register a callback for receiving notifications about received data using the nfc_p2p_set_data_received_cb() function. Place the registration code in the callback called after the P2P device is discovered.
    nfc_manager_set_p2p_target_discovered_cb(on_target_discovered, NULL);
    nfc_p2p_set_data_received_cb(target, on_p2p_data_received, NULL);
  3. Exchange messages:
    • Send a message to another device.

      When the other P2P device is attached, send the prepared message to it. You can use the nfc_p2p_send() function, if you do not want to check permissions.

      nfc_p2p_send(target, ndef_message, NULL, NULL);
    • Receive a message from another device.

      The callback about receiving data is invoked when the device receives a message. The callback provides a handle to the received message and a handle to the message source.

      To get a specified record from the message, use the nfc_ndef_message_get_record() function with the parameters for a message handle, a record index, and a handle to store the obtained record. When the record is obtained, get the stored text using the nfc_ndef_record_get_text() function.

      nfc_ndef_record_h ndef_record;
      char *name = NULL;
      nfc_ndef_message_get_record(message, 0, &ndef_record);
      nfc_ndef_record_get_text(ndef_record, &name);
      char *phone = NULL;
      nfc_ndef_message_get_record(message, 1, &ndef_record);
      nfc_ndef_record_get_text(ndef_record, &phone);
      char *email = NULL;
      nfc_ndef_message_get_record(message, 2, &ndef_record);
      nfc_ndef_record_get_text(ndef_record, &email);