Silent Push Notification in iOS 7 does not work

Question

In the WWDC 2013's "What's New with Multitasking" presentation, there is a section about Silent Push Notifications. It seems straight forward. According to the presentation, if you send the APS payload with just the content-available set to 1, users will not be notified of the notification.

// A. This doesn't work
{ 
  aps: { 
          content-available: 1 
       }
}

My testing shows that this does not work as no push is received. But if I include the sound attribute but exclude the alert attribute, it works (though not silent anymore).

// B. This works
{ 
  aps: {
          content-available: 1,
          sound: "default"
       }
}

However, if I change the sound attribute to play a silent audio, I can mimic a silent push.

// C. This works too.
{ 
  aps: {
          content-available: 1,
          sound: "silence.wav"
       }
}

Does anyone know:

1. If this a bug?
2. And if it is correct to assume that B or C is being treated as a Remote Notification (and not a bug with Silent Push where you need a sound attribute)? If so, this means it is not rate limited like Silent Pushes are... which Apple will likely fix. So I probably should not rely on it.
3. What the rate limit is (N pushes every X seconds, etc)?

Thanks in advance.

Edit with more information

For A, the state of the application does not matter. Notification is never received.

It seems like B and C only work if you enclose the attributes and values in quotes, like below.

{"aps":{"content-available": 1, "sound":"silent.wav"}}

And the notification arrives in application:didReceiveRemoteNotification:fetchCompletionHandler: regardless of state.

Answer 1

This works also and does not play a sound when it arrives:

{
    aps = {
        "content-available" : 1,
        sound : ""
    };
}

EDIT

People having this problem may want to check out this link. I have been participating in a thread on Apple's Developer forum that goes over all app states and when silent pushes are received and not received.

Answer 2

So I just came across this issue yesterday, and after trying sending a payload with a sound set to an empty string, it was still causing vibration/sound on the device. Eventually, I stumbled on a blog post from Urban Airship that suggested needing to send:

{ priority: 5 }

in the push notification, which I had never seen. After perusing Apple's docs for push notifications, I stumbled on this page:

https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CommunicatingwithAPNs.html

Which indicates that priority should be set as "5" or "10", and explains:

The notification’s priority. Provide one of the following values:

10 The push message is sent immediately.

The push notification must trigger an alert, sound, or badge on the device. It is an error to use this priority for a push that contains only the content-available key.

5 The push message is sent at a time that conserves power on the device receiving it.

Ultimately, we were able to get silent push notifications working with a badge count (and I suspect you could even do the same with an alert) with the following format:

    aps =     {
        badge = 7;
        "content-available" = 1;
        priority = 5;
    };

Answer 3

I have tried setting an empty string as the alert attribute and it also worked:

{
    aps =     {
        "content-available" = 1;
        "alert" = "";
    };
}

It seems like APNS is checking for the existence of this attributes for the purpose of validating the push payload. Interestingly, they are not checking the actual content. It seems a little bit hacky though...

Answer 4

I use the tool-Knuff send my push notification to my device.

It looks like:

Then,I tried these example.

They are all work!But you must set the priority 10!

So if you are not use the tool,you also note it.

---

examples:

• no alert,no sound

{
    "aps":{
        "content-available":1,
    }
}

• only alert

{
    "aps":{
        "content-available":1,
        "alert":""
    }
}

• only sound

{
    "aps":{
        "content-available":1,
        "sound":""
    }
}

Answer 5

This works for me:

{ 
  aps: { 
          content-available: 1 
       }
}

Look if you check Background fetch checkbox in Project Capabilities > Background Modes

Answer 6

I'm seeing the same problem. If I send a push with "content-available":1 and no other attributes set, the notification is never received. When I add any other attributes it works perfectly.

As a temporary work around I'm adding the badge attribute as this doesn't alert the user in any way apart from adding the badge to the icon.

Let me know if you've found a better solution.

Answer 7

Priority should be set as one item in binary stream but not in payload json string. Apparently only the latest type 2 format can be used in setting priority as follows:

$token      = chr(1) . pack('n', 32)     . pack('H*', $deviceToken);
$payload    = chr(2) . pack('n', strlen($json)) . $json;
$identifier = chr(3) . pack('n', 4)      . pack('N', $notification);
$expiration = chr(4) . pack('n', 4)      . pack('N', time()+86400);
$priority   = chr(5) . pack('n', 1)      . chr($priority);

$frame_data = $token.$payload.$identifier.$expiration.$priority;
$frame_length = strlen(bin2hex($frame_data))/2;

$msg = chr(2) . pack('N', $frame_length) . $frame_data;

Format types (first byte) for remote notification binary message:

0 - simple (old) 1 - enhanced (old) 2 - latest with more parameters (new)

Answer 8

Argh! Also pulling my hair out -- this isn't so much an answer as another example of a payload which DOESN'T work. The didReceiveRemoteNotification method is never called, although if the device is sleeping, the alert text IS displayed.

 {"aps":
    {  "alert":"alert!",
       "sound":"default",
       "content-available" : 1},
    "content-id":21482,
    "apt":"1"
}

"apt" is a custom field we use to indicate the notification type.

Answer 9

Setting 'sound' to 0 worked for me... :)

Answer 10

setting priority to 5 did not work for me, but setting sound or alert to an empty string did cause the notification to be handled as a high priority one

Answer 11

We had the same issue with no Notification being delivered. In our case we were using a silent push to update the badge number. When we set empty strings for alert (body and title) and sound it would work, but if any of the keys were not present it failed. Here is what worked, updating the badge with no sound or alert (log of the resulting userInfo dictionary in didReceiveRemoteNotification)

{
    aps =     {
        alert =         {
            body = "";
            title = "";
        };
        badge = 103;
        "content-available" = 1;
        sound = "";
    };
}