Calculating APNS frame sizes / formatting byte stream

Question

As per [ https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/CommunicatingWIthAPS.html#//apple_ref/doc/uid/TP40008194-CH101-SW4 ] the proper notification format appears to be:

OutputStream os; // assuming this connection is valid/open

// header
os.write(command);        // 1 byte    | value of 2 in doc but 1 in notnoop/java-apns ?
os.write(frame_length);   // 4 bytes   | value of total size of frame items:

// item 1 - token
os.write(item_id_1);      // 1 byte    | value of 1
os.write(item_length_1);  // 2 bytes   | value of size of data (32 for token):
os.write(item_data_1);    // 32 bytes  | token data
// = total frame item size: 35

// item 2 - payload
os.write(item_id_2);      // 1 byte    | value of 2
os.write(item_length_2);  // 2 bytes   | value of size of data (175 for my payload):
os.write(item_data_2);    // 175 bytes | payload data
// = total frame item size: 178

// item 3 - identifier
os.write(item_id_3);      // 1 byte    | value of 3
os.write(item_length_3);  // 2 bytes   | value of size of data (4)
os.write(item_data_3);    // 4 byte    | identifier data
// = total frame item size: 7

// item 4 - expiration date
os.write(item_id_4);      // 1 byte    | value of 4
os.write(item_length_4);  // 2 bytes   | value of size of data (4)
os.write(item_data_4);    // 4 byte    | expiration data
// = total frame item size: 7

// item 5 - priority
os.write(item_id_5);      // 1 byte    | value of 5
os.write(item_length_5);  // 2 bytes   | value of size of data (1):
os.write(item_data_5);    // 1 byte    | priority data
// = total frame item size: 4

Assuming that's all correct, that should give a frame data length total of: 35 + 178 + 7 + 7 + 4 = 232 by summing all of the frame item totals.

---

However in looking over some of the notnoop/java-apns code:

    public byte[] marshall() {
        if (marshall == null) {
            marshall = Utilities.marshallEnhanced(COMMAND, identifier,
                    expiry, deviceToken, payload);
        }
        return marshall.clone();
    }

    public int length() {
        int length = 1 + 4 + 4 + 2 + deviceToken.length + 2 + payload.length;

        //1 = ?
        //4 = identifier length
        //4 = expiration length
        //2 = ?
        //32 = token length
        //2 = ?
        //x = payload length

        final int marshalledLength = marshall().length;
        assert marshalledLength == length;
        return length;
    }

I fail to see how this is calculating the length correctly. My code however does not work while this presumably does. What am I doing wrong?

Answer 1

• First problem: I was examining an enhanced format (uses command 1) while trying to use a new format (uses command 2).

• Second problem: I wasn't using some form of ByteBuffering so the packet wasn't formed right.

The total frame size calculations were correct in both cases.