Make voice or video calls with a phone number: dial, wait for the other person to answer, then hang up. The operator updates the call status throughout.
The app calls the other person. The operator responds with a call ID and sends a call invitation to the recipient.
The other person answers, and the call connects.
Either person can hang up to end the call.
Agree on formatsWhen making and answering a call, both sides exchange media information to agree on audio and video formats.
Same actionThe caller cancelling, the recipient declining, and either person hanging up during a call all use the same end command.
WebRTC Call Handling: How it works
- CreateThe caller submits registrationId, both phone numbers, and offer. The operator responds with mediaSessionId.
- AnswerThe recipient uses PUT …/status to update the status, such as Ringing, and includes answer when connecting.
- EndEither person uses DELETE to cancel, decline, or hang up.
WebRTC Call Handling: API spec
POST /sessions to create; GET/DELETE /sessions/{mediaSessionId} to look up or end; PUT /sessions/{mediaSessionId}/status to update statusregistrationId (required); body: caller originatorAddress, recipient receiverAddress, media information offer.sdp| Response fields | Meaning | Example |
|---|---|---|
| mediaSessionId | Call ID generated by the operator network | 0AEE1B58BAEE… |
| status | Call status: Initial, InProgress, Ringing, Proceeding, Connected, Terminated, Hold, Resume, SessionCancelled, Declined, Failed, Waiting, NoAnswer, NotReachable, Busy | Connected |
| offer.sdp/answer.sdp | Media information from both sides (SDP) | v=0… |
| originatorAddress/receiverAddress | Communication addresses for the caller and recipient, such as phone numbers (tel:) or SIP URI | tel:+886912345678 |
Responses for three scenarios (excerpts)
InitialCall just created0AEE1B58BAEEDA3EABA42B32EBB3DFE0Call IDConnectedCall connectedv=0 …The other person's media information204Call endedSpec source: CAMARA WebRTC r2.2 (WebRTC Call Handling v0.3.0)
WebRTC Call Handling: 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 Call Handling's roleManages real-time voice and video calls.
Used together: WebRTC Registration, WebRTC Event Subscription
GSMA source ↗Sources: GSMA Open Gateway Use Case Library and API Descriptions (accessed 2026-10-14). Descriptions are summaries.