@Override
    public int hashCode() {
        return (21
               + 31 * identifier
               + 31 * expiry
               + 31 * Arrays.hashCode(deviceToken)
               + 31 * Arrays.hashCode(payload));
    }
Returns the length of the message in bytes as it is encoded on the wire.

Apple require the message to be of length 255 bytes or less.

@return length of encoded message in bytes
src/main/java/com/notnoop/apns/EnhancedApnsNotification.java