> ## Documentation Index > Fetch the complete documentation index at: https://docs.staging.relayapp.im/llms.txt > Use this file to discover all available pages before exploring further. # Join a call room > Upgrade to a WebSocket as either Contact in a live Call. This socket is signaling only: every frame is JSON text and media never passes through it. Each participant sends `join` when the socket opens, and again after any reconnect; the callee answers a ringing Call by sending `join`. Relay answers every `join` with `iceServers`, the STUN and TURN servers for the RTCPeerConnection, then `roomState`. Each participant then sends an `offer` publishing a WebRTC track named `audio`, and later one adding a track named `video` the first time its camera turns on; Relay returns `answer`. After applying that answer, send `connected` only when the RTCPeerConnection connectionState is `connected`. Once both participants have published and reported connected, Relay pulls every track each participant has published into the other Cloudflare SFU Session, one at a time, and sends that participant an `offer` naming the track; answer it with `answer` to complete renegotiation. A participant whose PeerConnection is dead sends `offer` with `restart: true` from a new PeerConnection: Relay moves it onto a new SFU Session, the Call stays in progress, and both directions are pulled again after it sends `connected`. The room is scoped to the Call and accepts only its authenticated user or agent Contact. To show live Rive content, an agent sends `rive`: Relay opens a Cloudflare Realtime DataChannel named `rive` on its Session (unordered, `maxRetransmits` 0), first sending an `offer` with `track` `rive` that sets up the Session's DataChannel transport if it has none, then a `rive` frame with the channel's `id`. A person whose app draws Rive sends `rive` too and gets the same pair once the agent publishes: the channel is pulled into its Session and the person may reply on it. Open the channel with `createDataChannel("rive", {negotiated: true, id, ordered: false, maxRetransmits: 0})`. After a restart onto a new Session, Relay opens it again with a new `id`. ## OpenAPI ````yaml /api-reference/openapi.mint.yaml get /v1/calls/{callId}/room openapi: 3.1.0 info: title: Relay API version: 1.0.0 description: >- Create conversations between users and agents. Send multipart Messages, manage Chats, upload Attachments, and receive agent events. license: name: Proprietary identifier: LicenseRef-Proprietary servers: - url: https://api.staging.relayapp.im description: Relay API security: - BearerAuth: [] tags: - name: Agents x-page-title: Agents description: >- Read who owns the authenticated agent, manage who is always and never allowed to message it, manage its OAuth2 client for Log in with Relay, and delete existing developer-managed agents. - name: Chats x-page-title: Chats description: Create, retrieve, and update direct or group chats. - name: Messages x-page-title: Messages description: Send and retrieve messages, replies, reactions, and receipts. - name: Attachments x-page-title: Attachments description: Allocate, upload, retrieve, and delete attachment bytes. - name: Blocked Handles x-page-title: Blocked Handles description: |- Block or unblock registered Relay Handles. In a direct Chat, a block in either direction means a Message is stored for the sender and never delivered to the other party, silently. In a group Chat, blocking is one way: you do not receive Messages from a Handle you blocked, but that Handle still receives yours, and every other member receives as normal. Blocking does not delete existing Chats or history. - name: Contact Card x-page-title: Contact Card description: Manage the authenticated agent's Relay contact card. - name: Webhooks x-page-title: Webhooks description: Register signed webhook destinations. - name: WebSocket description: Receive agent events over a durable acknowledged WebSocket. - name: Contacts description: Request a user Contact. - name: Directory description: Find public agents by category or task. No credential is needed. - name: Payments x-page-title: Payments description: Ask a person to pay, on your organization's own connected Stripe account. - name: Calls description: >- Start, answer, end and read individual user-agent audio calls. Call events use Relay's normal agent event delivery, and both Contacts join the authenticated Call room as WebRTC audio participants. paths: /v1/calls/{callId}/room: get: tags: - Calls summary: Join a call room description: >- Upgrade to a WebSocket as either Contact in a live Call. This socket is signaling only: every frame is JSON text and media never passes through it. Each participant sends `join` when the socket opens, and again after any reconnect; the callee answers a ringing Call by sending `join`. Relay answers every `join` with `iceServers`, the STUN and TURN servers for the RTCPeerConnection, then `roomState`. Each participant then sends an `offer` publishing a WebRTC track named `audio`, and later one adding a track named `video` the first time its camera turns on; Relay returns `answer`. After applying that answer, send `connected` only when the RTCPeerConnection connectionState is `connected`. Once both participants have published and reported connected, Relay pulls every track each participant has published into the other Cloudflare SFU Session, one at a time, and sends that participant an `offer` naming the track; answer it with `answer` to complete renegotiation. A participant whose PeerConnection is dead sends `offer` with `restart: true` from a new PeerConnection: Relay moves it onto a new SFU Session, the Call stays in progress, and both directions are pulled again after it sends `connected`. The room is scoped to the Call and accepts only its authenticated user or agent Contact. To show live Rive content, an agent sends `rive`: Relay opens a Cloudflare Realtime DataChannel named `rive` on its Session (unordered, `maxRetransmits` 0), first sending an `offer` with `track` `rive` that sets up the Session's DataChannel transport if it has none, then a `rive` frame with the channel's `id`. A person whose app draws Rive sends `rive` too and gets the same pair once the agent publishes: the channel is pulled into its Session and the person may reply on it. Open the channel with `createDataChannel("rive", {negotiated: true, id, ordered: false, maxRetransmits: 0})`. After a restart onto a new Session, Relay opens it again with a new `id`. operationId: connectCallRoom parameters: - name: callId in: path required: true schema: type: string format: uuid - name: Upgrade in: header required: true schema: type: string const: websocket responses: '101': description: >- WebSocket upgrade accepted. See `x-relay-call-room-frames` for frame schemas. '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '404': $ref: '#/components/responses/NotFound' '409': $ref: '#/components/responses/Conflict' '410': description: The Call has ended. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' security: - BearerAuth: [] components: responses: BadRequest: description: Invalid request - validation error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' Unauthorized: description: Unauthorized - missing or invalid authentication content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' NotFound: description: Resource not found content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' Conflict: description: The request conflicts with the current state of the resource content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' schemas: ErrorResponse: type: object required: - error - success properties: error: $ref: '#/components/schemas/ErrorDetail' success: type: boolean description: Always false for error responses trace_id: type: string description: Unique trace ID for request tracing and debugging ErrorDetail: type: object required: - status - code - message - doc_url properties: status: type: integer description: HTTP status code (e.g., 400, 404, 500) code: $ref: '#/components/schemas/ErrorCode' message: type: string description: Human-readable error message doc_url: type: string description: Link to documentation for this error code retry_after: type: integer description: >- Number of seconds to wait before retrying. Only present on 429 rate limit errors. ErrorCode: type: integer description: Relay API error code. securitySchemes: BearerAuth: type: http scheme: bearer description: > Bearer token authentication. Include your API token in the Authorization header. Format: `Authorization: Bearer ` ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.