Siperb Mobile — Push Notifications for Any PBX

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Getting missed calls on a mobile SIP softphone has been an unsolved problem for years. Either the app runs continuously in the background — draining the battery and eventually being killed by the operating system — or it goes silent and calls are missed entirely. Siperb’s mobile app now solves this properly: full push notification support for incoming calls on iOS and Android, working with any SIP PBX including Asterisk and FreePBX. And it’s free.

Why SIP on mobile has always been a problem

SIP is a stateful protocol — receiving an incoming call requires your device to be actively registered with the PBX at the moment the call arrives. On a desktop, that’s trivial. On mobile, it isn’t.

iOS and Android are both designed to suspend and terminate background processes to conserve battery. A SIP softphone running in the background will lose its registration within minutes — and when a call arrives, there’s nobody home. The workarounds people have tried — keeping the app permanently in the foreground, using persistent background services, shortening the SIP registration interval — all make things worse: more battery drain, more unreliability, more missed calls.

The correct solution is push notifications. It’s the same mechanism that makes your phone ring when someone calls your mobile number. The operating system manages the wake-up entirely; the app doesn’t need to stay alive. Until now, this has required deep integration between the PBX vendor and Apple or Google — something that put it out of reach for anyone running Asterisk or an open-source PBX. Siperb changes that.

How Siperb delivers push notifications for any PBX

When you register your PBX extension through Siperb, your mobile device registers with Siperb’s SIP proxy rather than directly with your PBX. The proxy maintains a persistent registration on your behalf — it stays alive so your app doesn’t have to.

When an incoming call arrives, the sequence is:

  1. Your PBX sends the SIP INVITE to Siperb’s proxy.
  2. Siperb’s proxy sends a push notification via Apple APNs (iOS) or Google FCM (Android).
  3. The operating system delivers the notification and wakes the Siperb app — even from a locked screen.
  4. The app re-registers and the call connects.

The push notification is just the wake-up signal — no call audio travels through Apple or Google’s servers. Audio flows directly between your device and your PBX (via Siperb’s transcoding layer if your PBX uses plain RTP rather than WebRTC).

Free on all plans: Push notifications are included on Siperb’s free Personal plan. No paid subscription is required.

What you need

  • Any SIP PBX — Asterisk, FreePBX, FreeSWITCH, 3CX, or any system that can provision a SIP extension
  • A free Siperb account — sign up at www.siperb.com/phone/
  • The Siperb mobile app — available for iOS and Android from the Downloads page

Firewall note: Your PBX must accept SIP registration from Siperb’s proxy IP addresses. If you’re running Asterisk, ensure your sip.conf or pjsip.conf permits external registration. See An Introduction to Connections for the proxy IP ranges and port details.

Setting it up

  1. Create a free account at www.siperb.com/phone/.
  2. Add a Connection — enter your PBX’s SIP credentials: host, extension number, and password. See Connecting Siperb to Your PBX for the full walkthrough.
  3. Download the Siperb app on your iOS or Android device from the Downloads page.
  4. Log in with your Siperb credentials — the app provisions itself automatically.
  5. Lock your phone and ask someone to call your extension. Your device will ring.

There is no server-side configuration required on your PBX beyond allowing the external registration. Siperb’s proxy handles the APNs and FCM integration entirely.

iOS and Android

Both platforms are fully supported, with platform-appropriate implementations:

  • iOS uses Apple’s VoIP push (PushKit), which the OS treats with the same priority as a native phone call — the app is woken immediately, even in low-power mode.
  • Android uses Firebase Cloud Messaging (FCM) with a high-priority flag, delivering the same reliable wake-up behaviour across manufacturers.

Both have been validated across locked screens, battery-saver modes, and after a full device restart.

Further reading