After the app subscribes to events, the operator sends notifications for incoming calls, call status changes, or registration ending.
Someone calls this phone number. The operator sends an incoming call invitation, and the app starts ringing.
When the call status changes, such as the other person putting it on hold, the operator sends a notification with the latest status.
When registration expires or is terminated by the network, the operator sends an end notification and the reason.
One event type per subscriptionCreate separate subscriptions for incoming calls, call status, and registration ending.
Required IDsAll require a registration ID; call status also requires a call ID.
WebRTC Event Subscription: How it works
- Create subscriptionThe app submits registrationId, the notification URL (sink), and one event type.
- Wait for an eventThe operator monitors incoming calls and call changes for this registration.
- Send notificationWhen an event occurs, the operator sends it to sink in CloudEvents format.
WebRTC Event Subscription: API spec
POST /subscriptions to create; GET /subscriptions to list; GET/DELETE /subscriptions/{subscriptionId} to look up or deleteprotocol (HTTP), sink, types (one event type), and config.subscriptionDetail.registrationId; also include sessionId when subscribing to call status| Event details | Meaning | Example |
|---|---|---|
| session-invitation | New incoming call, with the incoming phone number and call ID | …v0.session-invitation |
| session-status | Call status changed, with the latest status | Hold |
| registration-ends | Registration ended due to REGISTRATION_EXPIRED or NETWORK_TERMINATED | REGISTRATION_EXPIRED |
Responses for three scenarios (excerpts)
org.camaraproject.webrtc-events.v0.session-invitationIncoming call invitationtel:+886911222333Incoming phone numberorg.camaraproject.webrtc-events.v0.session-statusCall status updateHoldPut on holdorg.camaraproject.webrtc-events.v0.registration-endsRegistration endedREGISTRATION_EXPIREDExpiredSpec source: CAMARA WebRTC r2.2 (WebRTC Events v0.2.0)
WebRTC Event Subscription: GSMA use cases
Enhanced call experiences
Problem to solveLets any connected device make calls over the operator network, with or without a SIM card.
WebRTC Event Subscription's roleSubscribes to events to receive incoming call requests.
Used together: WebRTC Registration, WebRTC Call Handling
GSMA source ↗Sources: GSMA Open Gateway Use Case Library and API Descriptions (accessed 2026-10-14). Descriptions are summaries.