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.

Solution 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.

Solution 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;
    };

Solution 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...

Solution 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":""
    }
}

Solution 5

This works for me:

{ 
  aps: { 
          content-available: 1 
       }
}

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

View more solutions

Comments

[SG1]

Thanks for the link. There are multiple threads discussing this on ADC's Forums. Bottom line: there is a bug - after device restart - which an Apple rep has acknowledged should be fixed in an update (eventually).

[evalsyrelec]

If the app is in the background, and if you remove the 'alert' attribute, you should receive the callback in application:didReceiveRemoteNotification:fetchCompletionHand‌​ler:

[rjobidon]

Great answer Dave! A priority of 5 is allowed while "it is an error to use this priority [10] for a push that contains only the content-available key." developer.apple.com/library/ios/documentation/…

[Foriger]

Should be priority included in payload? IMO it is separete one byte in push you send.

[Sandy D.]

Priority does not get set in the payload. This gets set in the binary notification.

[malex]

In iOS7 it works great even without sound/alert keys. Content-avalable is sufficient key! But in iOS8 we have really strange behavior when even we set alert key with non-empty string in addition to "content-available" : 1 we get only banner with "alert" string, but "content-available" is ignoring for some reasons

[loretoparisi]

This solution with alert="" in the payload worked for me as well on iOS 9.0. The sound="" didn't work instead.

[emem]

I have had success with launching the app from notification with or without the added sound. Maybe, setting a sound, alert, or badge (empty or not) rises the default notification priority to 10, thus increasing its reliability. See what Apple says about pans-priority: developer.apple.com/library/ios/documentation/… The default priority is 10 (high), but it is an error to use this for push notification with only content-available key. So maybe the default is set to 5 if only the content-available key is set.

[Stony]

doesn't work on iOS10. I must push something to "sound".

[DaNLtR]

@mkwon and if I want to see the alert(regular push) while in BG + invoke application:didReceiveRemoteNotification:fetchCompletionHand‌​‌​ler: ? Tnx

[Slav]

Worked on iOS10 for me. But doesn't work now on iOS11

[Evan Kirkwood]

The link to the Apple Developer Forum thread in the edit seems to be dead. I know this is going back a long time now, but does anyone happen have an updated link (or title of that thread)?

[hgwhittle]

Worked for me, iOS 13