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{command: connect}\n Note right of CS: First protocol message.
Server decides to accept,
reject, or signal busy.\n\n alt Accepted\n CS->>SP: ConnectResponse
{command: answer}\n else Busy\n CS->>SP: ConnectResponse
{command: busy}\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n else Rejected\n CS->>SP: ConnectResponse
{command: reject}\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n end\n\n Note over SP,CS: Bidirectional Audio Streaming\n loop While call is active\n rect rgb(240, 240, 240)\n Note over SP,CS: Platform to Server Audio\n SP->>CS: [binary] AudioFrame
(16-bit signed PCM, mono, little-endian)\n Note right of CS: Recommended: 20ms frames.
8 kHz = 320 bytes/frame,
16 kHz = 640 bytes/frame.\n end\n\n rect rgb(240, 240, 240)\n Note over SP,CS: Server to Platform Audio\n CS->>SP: [binary] AudioFrame
(16-bit signed PCM, mono, little-endian)\n Note left of SP: Queued in playback buffer.
Max buffer: 5 MB per call.\n end\n\n rect rgb(240, 240, 240)\n Note over SP,CS: Stream Control (Server to Platform)\n alt Flush unplayed audio (e.g. interrupt)\n CS->>SP: StreamControl
{command: clear}\n Note left of SP: Discards buffered audio
not yet played to caller.\n else Keep-alive during silence\n CS->>SP: StreamControl
{command: heartbeat}\n Note left of SP: Prevents 1-minute
no-audio timeout.\n end\n end\n end\n\n Note over SP,CS: Call End\n Note over SP,CS: No reconnection mechanism.
Connection loss = call hung up.\n\n alt Customer closes connection\n CS->>SP: WebSocket close\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n else Sinch ends call\n SP->>CS: WebSocket close\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n end\n","diagramHtml":"Customer WebSocket ServerSinch PlatformCustomer WebSocket ServerSinch PlatformWebSocket ConnectionStream endedalt[WS accepted][WS rejected]Session StartFirst protocol message.Server decides to accept,reject, or signal busy.Stream endedStream endedalt[Accepted][Busy][Rejected]Bidirectional Audio StreamingPlatform to Server AudioRecommended: 20ms frames.8 kHz = 320 bytes/frame,16 kHz = 640 bytes/frame.Server to Platform AudioQueued in playback buffer.Max buffer: 5 MB per call.Stream Control (Server to Platform)Discards buffered audionot yet played to caller.Prevents 1-minuteno-audio timeout.alt[Flush unplayed audio (e.g.interrupt)][Keep-alive during silence]loop[While call is active]Call EndNo reconnection mechanism.Connection loss = call hung up.Stream endedStream endedalt[Customer closes connection][Sinch ends call]WS connect requestAccept connectionNon-success responseConnectRequest{command: connect}ConnectResponse{command: answer}ConnectResponse{command: busy}ConnectResponse{command: reject}[binary] AudioFrame(16-bit signed PCM, mono, little-endian)[binary] AudioFrame(16-bit signed PCM, mono, little-endian)StreamControl{command: clear}StreamControl{command: heartbeat}WebSocket closeWebSocket closeVoice Stream WebSocket Flow (Sinch Platform - Customer WebSocket Server)","diagramHtmlDark":"Customer WebSocket ServerSinch PlatformCustomer WebSocket ServerSinch PlatformWebSocket ConnectionStream endedalt[WS accepted][WS rejected]Session StartFirst protocol message.Server decides to accept,reject, or signal busy.Stream endedStream endedalt[Accepted][Busy][Rejected]Bidirectional Audio StreamingPlatform to Server AudioRecommended: 20ms frames.8 kHz = 320 bytes/frame,16 kHz = 640 bytes/frame.Server to Platform AudioQueued in playback buffer.Max buffer: 5 MB per call.Stream Control (Server to Platform)Discards buffered audionot yet played to caller.Prevents 1-minuteno-audio timeout.alt[Flush unplayed audio (e.g.interrupt)][Keep-alive during silence]loop[While call is active]Call EndNo reconnection mechanism.Connection loss = call hung up.Stream endedStream endedalt[Customer closes connection][Sinch ends call]WS connect requestAccept connectionNon-success responseConnectRequest{command: connect}ConnectResponse{command: answer}ConnectResponse{command: busy}ConnectResponse{command: reject}[binary] AudioFrame(16-bit signed PCM, mono, little-endian)[binary] AudioFrame(16-bit signed PCM, mono, little-endian)StreamControl{command: clear}StreamControl{command: heartbeat}WebSocket closeWebSocket closeVoice Stream WebSocket Flow (Sinch Platform - Customer WebSocket Server)"},"children":["sequenceDiagram\n title Voice Stream WebSocket Flow (Sinch Platform - Customer WebSocket Server)\n participant SP as Sinch Platform\n participant CS as Customer WebSocket Server\n\n Note over SP,CS: WebSocket Connection\n SP->>CS: WS connect request\n alt WS accepted\n CS-->>SP: Accept connection\n else WS rejected\n CS--xSP: Non-success response\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n end\n\n Note over SP,CS: Session Start\n SP->>CS: ConnectRequest
{command: connect}\n Note right of CS: First protocol message.
Server decides to accept,
reject, or signal busy.\n\n alt Accepted\n CS->>SP: ConnectResponse
{command: answer}\n else Busy\n CS->>SP: ConnectResponse
{command: busy}\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n else Rejected\n CS->>SP: ConnectResponse
{command: reject}\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n end\n\n Note over SP,CS: Bidirectional Audio Streaming\n loop While call is active\n rect rgb(240, 240, 240)\n Note over SP,CS: Platform to Server Audio\n SP->>CS: [binary] AudioFrame
(16-bit signed PCM, mono, little-endian)\n Note right of CS: Recommended: 20ms frames.
8 kHz = 320 bytes/frame,
16 kHz = 640 bytes/frame.\n end\n\n rect rgb(240, 240, 240)\n Note over SP,CS: Server to Platform Audio\n CS->>SP: [binary] AudioFrame
(16-bit signed PCM, mono, little-endian)\n Note left of SP: Queued in playback buffer.
Max buffer: 5 MB per call.\n end\n\n rect rgb(240, 240, 240)\n Note over SP,CS: Stream Control (Server to Platform)\n alt Flush unplayed audio (e.g. interrupt)\n CS->>SP: StreamControl
{command: clear}\n Note left of SP: Discards buffered audio
not yet played to caller.\n else Keep-alive during silence\n CS->>SP: StreamControl
{command: heartbeat}\n Note left of SP: Prevents 1-minute
no-audio timeout.\n end\n end\n end\n\n Note over SP,CS: Call End\n Note over SP,CS: No reconnection mechanism.
Connection loss = call hung up.\n\n alt Customer closes connection\n CS->>SP: WebSocket close\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n else Sinch ends call\n SP->>CS: WebSocket close\n rect rgb(255, 204, 204)\n Note over SP,CS: Stream ended\n end\n end\n"]}]},"headings":[{"value":"Voice Stream Control","id":"voice-stream-control","depth":2},{"value":"Connection Flow Diagram","id":"connection-flow-diagram","depth":3}],"frontmatter":{"seo":{"title":"Voice Stream Control"}},"lastModified":"2026-08-31T13:48:15.000Z","pagePropGetterError":{"message":"","name":""}},"slug":"/docs/voice-2.0/api-reference/x-voice-stream/str_connection_flow","userData":{"isAuthenticated":false,"teams":["anonymous"]},"isPublic":true}