Android | Not reachable when screen is off

+2 votes


I have an issue with incoming Zoiper calls using SIP on WiFi on different devices (for example Samsung Galaxy A3).

When the screen is off, about one tenth of the incoming calls receive the busy signal. Often, the moment when the calling party receives the busy signal, the phone starts ringing but cannot be picked up.

Have had this happen on old and newest Zoiper versions, Android 6 and 7.

Changing into TCP or UDP does not make a difference either.

Zoiper is removed from the "optimize battery" list and Android Doze is disabled.

If I keep the phone screen turned on all the time, this does not happen. It only happens when the screen is off.

It took a while until I was able to pinpoint the issue - would greatly appreciate some help!


asked Jan 29, 2018 in Android by kreshnik (180 points)  


Do you have keep alive wifi, stay awake and run in background enabled at the connectivity settings?



Hi Paul,

Yes, all three are enabled have have always been.

Best regards,

Hi Kreshnik,

Any other software installed using voip technology?



There is a setting on samsung phones to turn off the wifi when the screen is off in Wifi -> Advanced Settings.

Also I would ping the phone form a pc / laptop and see if it keeps responding while the screen is off.

Hi Paul,

No, just the normal apps that came with the phone. Not even Skype or Whatsapp are installed in this particular device.




So the ping test did reveal, I believe, what the problem is. It seems that Android degrades the performance of wifi when on sleep (even though set to "keep it alive"). Here are the results of the ping:

Antwort von Bytes=32 Zeit=13ms TTL=63
Antwort von Bytes=32 Zeit=311ms TTL=63
Antwort von Bytes=32 Zeit=210ms TTL=63
Zeitüberschreitung der Anforderung.
Antwort von Bytes=32 Zeit=116ms TTL=63
Antwort von Bytes=32 Zeit=39ms TTL=63
Antwort von Bytes=32 Zeit=57ms TTL=63
Antwort von Bytes=32 Zeit=191ms TTL=63
Antwort von Bytes=32 Zeit=6ms TTL=63
Antwort von Bytes=32 Zeit=35ms TTL=63
Zeitüberschreitung der Anforderung.
Antwort von Bytes=32 Zeit=167ms TTL=63
Zeitüberschreitung der Anforderung.
Antwort von Bytes=32 Zeit=313ms TTL=63

I made the same test in a completely other device, too: Xiaomi Redmi Note 3 wifi same wifi sleep policy - same result.

I searched for some Google connectivity service that might be "battery optimized", but I cannot find any settings that might have to do something with this.

Only setting the ping timout to 10 seconds seems to make sure that every ping request is answered. But there are often very long delays:

Antwort von Bytes=32 Zeit=5608ms TTL=64

Does anyone have any idea what can be done here to have Android "wake" its wifi more often?




Did you already tried : Settings --> Accu(Battery) -->Power saving management-->setting icon -->Smart memory clean up?

This helped me.



I tested the issue with pings, too:

1. Test:

When pinging the whole time to my phone it rings immediately on any call. But now the phone is mostly awake and does not sleep at all.

2. Test:

I let the phone sleep for about 5min. Then starting an incoming call. Phone still sleeps. Now I start pinging the phone at the same time as the call waits and now the phone wakes up from the pings and rings.

4 Answers

0 votes


I have the exact same problem. Until autumn 2017 all worked fine for several years.

Now I can not longer rely on Zoiper on incoming calls on my Xiaomi Redmi Note 3 SE/Kate, although I set all the settings for not sleeping, not battery saving etc within MIUI.

At the moment I use Grandstream wave as 2nd VoIP-client, which works fine, but has big addressbook issues. So GS wave is only used to wake up my device on incoming calls and when the screen goes on Zoiper also starts to ring - at least most of the time.

That's kind of strange solution, but until now the Zoiper team did not really react to this issue. Today I got an update for Zoiper which has a switch to not let the phone sleep at all - which is totally out of acceptance, because it will drain the battery within few hours.

I don't understand why they cannot fix this, as it worked fine in the past and others like Grandstream also can do it.

answered Mar 26, 2018 by Pholio (150 points)  


Did you tried to change your beacon interval on your router?

Depending on your actual network usage, you may also need a lower beacon interval for such as VoIP, mobile phones that pick up calls.

You do not want to setup your wifi network configuration in such a way that your devices wake up every 10 minutes to pick up calls or notifications.

I am using a Fritzbox as Sip-Server, so there is no need for such settings, because sip-sessions stay inside the local network. Also I am not able to change these settings in the Fritzbox.

0 votes

I did some tests. Using zoiper exact version "Zoiper rv2.8.70-mod" on a Moto G4. Enabling only wifi (no cell data). I own and manage the PBX so I did a trace on PBX side.

Sometimes no incoming call on zoiper, and sometimes incoming call arrives many seconds later.

Everycase, zoiper reply to SIP INVITE with TRYING, but no RINGING sip packet or is very late. You can see the timing capture on the link below. In that case RINGING packet was 7 second later.

Capture attached

So, I don't thing this would be only a "sleep" android issue, because zoiper always replies to INVITE.

answered Mar 28, 2018 by elkato (140 points)  

I agree. As I mentioned Zoiper immediately starts ringing when I manually activate the phone by pressing the power button. Seems that Zoiper has a problem in waking up the device to ring.

@elkato, can you please send us an email to "android   (at)  zoiper  (dot)  com" with a mention of this topic and the exact issue. 

Elkato, does it even happen to you that Zoiper starts ringing, but the calling party shows that the Zoiper extension is busy? Picking up in Zoiper starts the timer but of course no audio is being exchanged because for the other caller the call has ended.

This only happens when Zoiper is called when the android screen is off.

0 votes

The alarm settings will schedule an alarm every 30 seconds to wake up Zoiper. This method does not work reliably on all phones, android version and targetted SDK versions and might depend on other factors such as memory usage, battery left etc. After Zoiper checks for incoming calls.

The issue above is not with Zoiper, it is the phone not waking up the application (on time). 

In the case of elkato, it seems like a different issue zoiper is actually woken up, but not given enough cpu time to get to the ringing part and we would like to investigate that more. 

With the constant wakelock, zoiper will be active all the time but will be using minimal cpu. Battery usage will inevitably be more but it will not cause the battery to drain in a few hours.

answered Mar 28, 2018 by root (1,720 points)  

The API used is the same as the others and the same as in zoiper 1. The phone decides when to wake up zoiper and when not. Values under 2 minutes are unreliable. 

We have no control over it and we do not know how the decision is made, only that it seems very random. What works on one phone most likely won't work on another one and the other way around. 

The decision might be made based on different API levels, firmware, hardware, battery levels, memory usage, we have no idea. 

Why do you not talk about those 2 points:

  1. An older version of Zoiper did work for several years on my phone. Since mid/end 2017 it stopped working normally and since then I miss most of the calls.
  2. Grandstream wave has none of these issues. So why should Zoiper?

Honestly, I only hesitate to use wave because it has dialing/addressbook issues. If this is solved, there is not really something preventing me to switch over to Grandstream wave, although I bought several Zoiper licenses and really liked the app. But without incoming calls (without wakelock) a phone app is totally useless.

I spoke about those points, but you are not listening. There is NOTHING we can do. Your phone is not waking up some applications reliably for whatever reason. 

It used to work with Zoiper and we haven't changed the method. The method used is the same as the other brands do. The phone is randomly deciding not to wake up the application. 

I will send you some old versions of Zoiper to play with. 

Have a look here, it explains it a bit more:

From:,%20long, )


To reduce abuse, there are restrictions on how frequently these alarms will go off for a particular application. Under normal system operation, it will not dispatch these alarms more than about every minute (at which point every such pending alarm is dispatched); when in low-power idle modes this duration may be significantly longer, such as 15 minutes.

For reliable incoming calls with udp, we need to re-register every 30s to keep the NAT open. If we were to use 1 minute instead of 30s it would probably work most of the time, the calls would work for some people (with routers with high nat timeout) but would not work all the time for users with lower nat timeout.

Thanks, I will try the old versions.

As I am using the same phone I cannot explain, why it did work, even a long time with Zoiper 2.0 beta it worked. Little time after the official 2.0 release the problems startet.

0 votes

We just released zoiperbeta with experimental push proxy support. Could take a few hours to propagate to all beta users.

Important to know, we do not transmit your password to our servers, unlike the other softphones do, so even if we get hacked, nobody will be able to steal your password as we don't have it.

This option will require a subscription once released as stable. (we need to proxy all communications for that).

Be sure to go to connectivity settings and enable the push in the settings.
answered Apr 24, 2018 by root (1,720 points)  
edited May 3, 2018 by root

thanks for effort, installed beta version, same when screen turn off a while. always busy tone.

When turning screen on, becomes reachable. 

Have you activated the PUSH service from Zoiper -> Settings -> Connectivity ? 

yes. tried everything: keep wifi alive, run in background, use tcp.......set registry expire time to 120s.

after sleeping a while,  zoiper becomes unreachable, always busy tone.

This issue perhaps from android 8, zoiper works great in android 7 and 6.  After upgrading to andriod 8(Oreo), such problem occurs. however it's interesting I tried zoiper on LG pad (android8), works well.

FYI, my cellphone is huawei mate9. 

What about the PUSH option, have you tried it ?

yes, tried. but nothing changed and the problem still there.

perhaps either Huawei or Oreo killed/interfered Zoiper in some way.

With the PUSH notification, there should be no issues. By the way, when you enable the PUSH proxy, is everything working correctly for you ? Do you see warning that the registration expiry time is too short ?  If yes, this means that your VoIP provider has maximum allowed registration expiry time shorter than the recommended value of 10 minutes and your phone may kill Zoiper or may not work correctly.


I have the same problem on my Huawei P9 (Android 6) with Zoiper Pro and Zoiper Free. It seems to be a general problem - SipGo, CSipSimple, Sipdroid etc. have the same issue. The best result I have is, when I run an older version of Zoiper Free on my Huawei (unfortunately it works not every day properly...), or when I using my other, older device with Android 4.4.2 (works fine and stable everyday).

Additionally I have a question about Zoiper Beta: "Could take a few hours to propagate to all beta users." = how many hours? After install I am waiting ca. 4 hours and get by calling my voip number still "Sorry, the number you dialed didn't respond." Not even my voice mail on the VoIP account (should be if out of range or phone is off), but only "didn't respond". Outgoing calls are OK and Zoiper Beta works - after uncheck "push service" - quite stable with outgoing and incoming calls.

Any suggestions?


After installing Zoiper Beta I run on my Huawei P9 Zoiper Beta AND Zoiper Free/Pro (one of them simultaneously with Zoiper Beta). It seems to be better, because Zoiper Free works in background stable and goes not asleep even after one or two hours the screen is locked (Zoiper Pro is going asleep “as usually”).
By an incoming call I see only the UI of Zoiper Free, Zoiper Beta seems to be only a kind of support with the push service.
It's funny and it is more a workaround then a really solution, but it works :)

Zoiper Beta works as a stand alone app not properly - it runs, but if the push service is active, there are no incoming calls, only the voice mail of my voip account.

"warning that the registration expiry time is too short " didn't see this.

I tried everything I can do, but either zoiper or ziper beta became unreachable after screen off some time.

My solution: downgrade my mate9 to android 7, reset as new phone ( restoring from backup had same problem), and use old version zoiper. works great again.

by the way, zoiper on my LG pad (android oreo) works well at the beginning, but became unreachable after 5-6 hours. 

Hence, two reasons perhaps:

1. Android oreo kills zoiper

2. other apps draw over zoiper ( I am not sure, but turn off this feature of all other apps)

Moreover, probably you could add below features as options ：

1. turn on screen when registering with server

2. let notification LED light on when missing a call (like GMAIL has new email)

I found zoiper couldn't be waked up if some other apps running in background when screen off.

so you might clean all other apps in background if plan to let your phone sleep long time.


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