WebAPI/WebNFC

First iteration: NDEF

Scope

• Technologies:
  • Focus on NDEF standard only for now
  • Others (e.g. proprietary MIFARE) to be investigated later.
• Capabilities:
  • Read/write NDEF records on tags
  • P2P NDEF push/receive
• Implementation:
  • NDEF-only API available on navigator.mozNfc object
  • Discovered NDEF tags are automatically parsed and dispatched to content in the "ndefdiscovered" event on navigator.mozNfc
  • navigator.mozNfc only available to a specific privileged content page (cf. WebTelephony, WebSMS).
  • For now, content is expected to do filtering and dispatching to handlers e.g. via WebIntents/WebActions/postMessage

Proposed API

navigator.mozNfc has one event restricted to NDEF discovery. The "ndefdiscovered" NfcNdefEvent will be fired when a new NDEF message is discovered either via reading a tag or receiving it via P2P communication. The event will contain an array of the received NfcNdefRecords. There are two functions to write NDEF records either to a tag or push them as P2P message.

 interface Nfc
 {
   attribute EventListener onndefdiscovered;
   attribute EventListener onndefdisconnected;
 
   nsIDOMDOMRequest writeNdefTag(in NfcNDefRecords[] records);
   nsIDOMDOMRequest ndefPush(in NfcNDefRecords[] records);
 };

 interface NfcNdefEvent : nsIDOMEvent
 {
   readonly attribute NfcNDefRecords[] ndefRecords;  
 };

NDEF records contain a bunch of metadata and a payload that is exposed as a string.

 interface NfcNdefRecord 
 {
   readonly attribute octet tnf;
   readonly attribute DOMString type;
   readonly attribute DOMString id;
   readonly attribute DOMString payload;
 };

NDEF Read Example

 navigator.mozNfc.onndefdiscovered = function (event) {
   console.log("Discovered an NDEF message with " + event.ndefRecords.length + " records.");
   event.ndefRecords.forEach(function (record) {
     console.log("Found a " + record.tnf + " record" +
                 " of type " + record.type +
                 " with ID " + record.id +
                 " and payload " + record.payload);
     // Could dispatch event.message here to other web apps based on MIME type, URI, etc.
   });
 };

NDEF Write Tag Example

 navigator.mozNfc.onndefdiscovered = function (event) {
   var ndefRecords = [ new MozNdefRecord(1, "U", "", "\u0000http://mozilla.org") ];
   var domreq = navigator.mozNfc.writeNdefTag(ndefRecords);
   domreq.onsuccess = function(e) {
     console.log("Successfully wrote records to tag");
   }
   domreq.onerror = function(e) {
     console.log("Write failed!");
   }
 };

NDEF P2P Push Example

 var ndefRecords = [ new MozNdefRecord(1, "U", "", "\u0000http://mozilla.org") ];
 var domreq = navigator.mozNfc.ndefPush = function (event) {
 domreq.onsuccess = function(e) {
   console.log("Successfully pushed P2P message");
 }
 domreq.onerror = function(e) {
   console.log("P2P push failed!");
 }

Implementation

• See bug 674741
• Engineers: Markus Neubrand, Arno Puder, Garner Lee, Siddartha Pothapragada, Philipp von Weitershausen