Intel® Collaboration Suite for WebRTC: Open WebRTC Toolkit (OWT) Client-Portal Protocol

Published: 01/10/2022

 1. Overview

This documentation covers all signaling messages between Client and MCU component through connections.

2. Terminology

Here is a table describing the detailed name and definition.

Name Definition
Portal The MCU component listening at the server port, accepting signaling connections initiated by Clients, receive/send signaling messages from/to Clients.
Client The program running on end-user’s device which interacts with MCU Server by messages defined in this documentation.
Signaling Connection The signaling channel between Client and Portal established by Client to send, receive and fetch signaling messages.
Room The logical entity of a conference in which all conference members (participants) exchange their video/audio streams, and where mixed streams are generated. Every room must be assigned with a unique identification **(RoomID)** in the MCU scope.
User The service account defined in the third-party integration application. The user ID and user role must be specified when asking for a token.
Participant The logical entity of a user when participating in a conference with a valid token. Every participant must be assigned with a unique identification **(ParticipantID)** in the room scope, and must be assigned a set of operation permissions according to its role.
Token The credential when a particular participant requests to join a particular room. It must contain a unique identification, the hostname of the target portal which can be used to connect, and the checksum to verify its validity.
Stream The object represents an audio and/or video media source which can be consumed (say, be subscribed, recorded, pushed to a live stream server) within a room. A stream can be either a participant published one which is called a Forward Stream, or a room generated one which is called a Mixed Stream. A stream object must be assigned with a unique identification **(StreamID)** in the room scope, Participants can select a particular stream to subscribe according to StreamID. A stream must also contain the audio information of the codec, sample rate, channel number, and video information about codec for Forward Stream or about codec, resolution, frame rate, key frame interval, quality level for Mixed Stream. Participants can determine whether the stream fulfill their expectation based on such information.
Subscription The activity a participant consuming a stream, such as receiving a stream via a WebRTC PeerConnection, recording a stream to a MCU storage, pushing a stream to a live stream server. A unique identification **(SubscriptionID)** in the room scope must be assigned to the subscription once its request is accepted by MCU. Participants will use the identification to update/cancel/stop a specific subscription.
Session The entity in which a real-time audio/video communication takes place. Typically, participants establish WebRTC sessions between a WebRTC client and MCU (accurately, the webrtc-agent) to publish or subscribe streams. Since a stream ID will be assigned when publishing a stream into a room and a subscription ID will be assigned when subscribing a stream (or a pair of stream if audio and video come from different source), the stream ID and subscription ID in these two cases are re-used to identify the corresponding session, and MCU must guarantee that the stream IDs and subscription IDs will not conflict within a room.


3. Signaling

3.1 Format

3.1.1 Client -> Portal

Given that Client has connected Portal successfully and the socket object is ready to send/receive data to/from Portal, Client must send all signaling message to Portal by calling the client socket object’s emit method in the following format (javascript code for example, same for rest of this documentation):

clientSocket.emit( RequestName, RequestData, function(ResponseStatus, ResponseData) { //Handle the status and response here. } );


  • RequestName must be with type of string, and with value defined in this specification;
  • RequestData must be with type of javascript object (or equivalent in other programming language), and with format defined in this specification. And will be absent if no request data is required;
  • ResponseStatus must be with value either “ok” or “error”;
  • ResponseData must be with type of javascript object or undefined if ResponseStatus equals to “ok”, and with type of ErrorDescription object defined as following if ResponseStatus equals to “error”.

    object(ErrorDescription):: { code: number(ErrorCode), description: string(Reason) }

    3.1.2 Portal -> Client

    Given that Portal has accepted Clients connecting and the socket object is ready to send/receive data to/from Client, Portal must send all signaling messages to Client by calling the server socket object’s emit method in the following format:

    serverSocket.emit( NotificationName, NotificationData ); Note:

  • NotificationName must be with type of string, and with value defined in this specification;
  • NotificationData must be with type of object, and with format defined in this specification, and will be absent if no notification data is present.

3.2 Connection Maintenance

3.2.1 Client Connects

Portal should be able to listen at either a secure or an insecure server port to accept Clients’ connecting requests. If the secure server is enabled, the SSL certificate and private key store path must be correctly specified by configuration item portal.keystorePath in portal.toml. server needs pop a 'connection' event indicating a new client’s successfully connected.

3.2.2 Client Keeps Alive server has its own underlying connection keep-alive mechanism, so no application level heart-beat is needed. But Client needs to refresh the reconnection ticket periodically before the current one expires if it wants to reconnect to Portal in case the network break or switch happens.

  The refreshing request must keep to the following format:

RequestName: "refreshReconnectionTicket" RequestData: absent ResponseData: A refreshed base64-encoded ReconnectionTicket object if ResponseStatus is "ok".

3.2.3 Client Disconnects

The connected object at server side will be notified with a ‘disconnect’ event. The waiting for reconnecting timer **(Timer100)** will be started right after receiving the ‘disconnect’ event if the following conditions are fulfilled:

  • The connection is initiated from a mobile client;
  • No participant leaving signaling has been received. Note:
    If Client has not reconnected successfully before Timer100 expires, Portal will not wait for and accept the Client’s reconnection any longer. Otherwise, if Client reconnects successfully before Timer100 expires, Portal will resume all the signaling activities with Client and kill Timer100.

    3.2.4 Client Reconnects

This a format for client reconnects.

RequestName: "relogin"

RequestData: The ReconnectionTicket object defined in 3.3.1 section.

ResponseData: A refreshed base64-encoded ReconnectionTicket object if ResponseStatus is "ok".

3.3 Conferencing

3.3.1 Participant Joins a Room

RequestName: “login”

RequestData: The LoginInfo object with following definition:

object(LoginInfo):: { token: string(Base64EncodedToken), userAgent: object(ClientInfo), reconnection: object(ReconnectionOptions)/*If reconnection is required*/ | false/*If reconnection is not required*/ | undefined/*For compatibility (with 3.4 clients) purpose, will be considered as false or {keepTime: -1}*/, protocol: string(ProtocolVersion)/*e.g. “1.1”*/ | undefined/*For compatibility (with 3.4 clients) purpose, will be considered as "legacy"*/ }

object(ClientInfo):: { sdk: { type: string(SDKName), version: string(SDKVersion) }, runtime: { name: string(RuntimeName), version: string(RuntimeVersion) }, os: { name: string(OSName), version: string(OSVersion) } }

object(ReconnectionOptions):: { keepTime: number(Seconds)/*-1: Use server side configured 'reconnection_timeout' value; Others: specified keepTime in seconds*/ } ResponseData: The LoginResult object with following definition if ResponseStatus is "ok":

   id: string(ParticipantId),
   user: string (UserId),
   role: string(ParticipantRole),
   permission: object(Permission),
   room: object(RoomInfo),
   reconnectionTicket: undefined/*when reconnection is not promised*/
                  | string(Base64Encoded(object(ReconnectionTicket)))/*when reconnection is promised*/

     publish: {
         audio: true | false,
         video: true | false
     subscribe: {
         audio: true | false,
         video: true | false

     id: string(RoomId),
     views: [string(ViewLabel)],
     streams: [object(StreamInfo)],
     participants: [object(ParticipantInfo)]

       id: string(StreamID),
       type: "forward" | "augmented" |"mixed",
       media: object(MediaInfo),
       info: object(PublicationInfo)/*If type equals "forward"*/
            | object(AugmentInfo)/*If type equals "augmented"*/
            | object(ViewInfo)/*If type equals "mixed"*/

         audio: object(AudioInfo) | undefined,
         video: object(VideoInfo) | undefined

           status: "active" | "inactive" | undefined,
           source: "mic" | "screen-cast" | "raw-file" | "encoded-file" | undefined,
           format: object(AudioFormat),
             format: [object(AudioFormat)] | undefined
            | undefined

             codec: "pcmu" | "pcma" | "opus" | "g722" | "iSAC" | "iLBC" | "aac" | "ac3" | "nellymoser",
             sampleRate: number(SampleRate) | undefined,
             channelNum: number(ChannelNumber) | undefined

           status: "active" | "inactive" | undefined,
           source: "camera" | "screen-cast" | "raw-file" | "encoded-file" | undefined,
           original: [{
             format: object(VideoFormat),
             parameters: object(VideoParameters) | undefined,
             simulcastRid: string(SimulcastRid) | undefined
              format: [object(VideoFormat)] | undefined,
                 resolution: [object(Resolution)] | undefined,
                 framerate: [number(FramerateFPS)] | undefined,
                 bitrate: [number(BitrateKbps)] | [string(BitrateMultiple)] | undefined,
                 keyFrameInterval: [number(KeyFrameIntervalSecond)] | undefined
                | undefined
             | undefined

             codec: "h264" | "h265" | "vp8" | "vp9",
             profile: "B" | "CB" | "M" | | "E" | "H" //If codec equals "h264".
                   | undefined //If codec does NOT equal "h264"

             resolution: object(Resolution) | undefined,
             framerate: number(FramerateFPS) | undefined,
             bitrate: number(BitrateKbps) | undefined,
             keyFrameInterval: number(KeyFrameIntervalSecond) | undefined

               width: number(WidthPX),
               height: number(HeightPX)

         owner: string(ParticipantId),
         type: "webrtc" | "streaming" | "sip",
         inViews: [String(ViewLabel)],
         attributes: object(ClientDefinedAttributes)

        origin: String(OriginStreamId),
        description: String(EffectDescription)

         label: string(ViewLable),
         activeInput: string(StreamId) | "unknown",
         layout: [object(MixedVideoLayout)]

           stream: string(StreamId) | undefined/*If this region is empty*/,
           region: object(Region)

             id: string(RegionId),
             shape: "rectangle" | "circle",
             area: object(Rectangle)/*If shape equals "rectangle"*/
                   | object(Circle)/*If shape equals "circle"*/

               left: string(LeftRatio),
               top: string(TopRatio),
               width: string(WidthRatio),
               height: string(HeightRatio)

               centerW: string(CenterWRatio),
               centerH: string(CenterHRatio),
               radius: string(RadiusWRatio)

       id: string(ParticilantId),
       role: string(ParticipantRole),
       user: string (UserId)

     ParticipantId: string(Participantid),
     ticketId: string(RandomNumber),
     notBefore: number(ValidTimeBegin),
     notAfter: number(ValidTimeEnd),
     signature: string(Signature)

3.3.2 Participant Leaves a Room

RequestName: “logout”

RequestData: absent

ResponseData: undefined if ResponseStatus is “ok”.

3.3.3 Participant Is Dropped by MCU

NotificationName: “drop”

NotificationData: absent

3.3.4 Participant Is Notified on Other Participant’s Action

NotificationName: “participant”

NotificationData: The ParticipantAction object with following definition:

object(ParticipantAction):: { action: "join" | "leave", data: object(ParticipantInfo)/*If action equals “join”*/ | string(ParticipantId)/*If status equals "leave"*/ }

3.3.5 Participant Sends a Text Message

RequestName: “text”

RequestData: The TextSendMessage object with following definition:

object(TextSendMessage):: { to: string(ParticipantId) | "all", message: string(Message) /*The message length must not greater than 2048*/ } ResponseData: undefined if ResponseStatus is “ok”.

3.3.6 Participant Receives Text Message from another Participant

NotificationName: “text”

NotificationData: The TextReceiveMessage object with following definition:

object(TextReceiveMessage):: { from: string(ParticipantId), to: 'me' | 'all', message: string(Message) }

3.3.7 Participant Starts Publishing a WebRTC Stream to Room

RequestName: “publish”

RequestData: The PublicationRequest object with following definition:

object(PublicationRequest):: { media: object(WebRTCMediaOptions), attributes: object(ClientDefinedAttributes) }

object(WebRTCMediaOptions):: { audio: { source: "mic" | "screen-cast" | "raw-file" | "encoded-file" } | false, video: { source: "camera"| "screen-cast" | "raw-file" | "encoded-file", parameters: { resolution: object(Resolution), framerate: number(FramerateFPS) } } | false } ResponseData: The PublicationResult object with following definition if ResponseStatus is “ok”:

object(PublicationResult):: { id: string(SessionId) //will be used as the stream id when it gets ready. }

3.3.8 Participant Stops Publishing a Stream to Room

RequestName: “unpublish”

RequestData: The UnpublicationRequest object with following definition:

object(UnpublicationRequest):: { id: string(SessionId) //same as the stream id. } ResponseData: undefined if ResponseStatus is “ok”.

3.3.9 Participant Is Notified on Streams Update in Room

NotificationName: “stream”

NotificationData: The StreamUpdateMessage object with following definition.

object(StreamUpdateMessage):: { id: string(StreamId), status: "add" | "update" | "remove", data: object(StreamInfo)/*If status equals "add"*/ | object(StreamUpdate)/*If status equals "update"*/ | undefined /*If status equals "remove"*/ }

object(StreamUpdate):: { field: "audio.status" | "video.status" | "video.layout" | "activeInput" | ".", value: "active" | "inactive" | [object(MixedVideoLayout)] | string(inputStreamId) | object(StreamInfo) }

3.3.10 Participant Controls a Stream

RequestName: “stream-control”

RequestData: The StreamControlInfo object with following definition:

object(StreamControlInfo):: { id: string(StreamId), // Must refer to a forward stream operation: "pause" | "play", data: ("audio" | "video" | "av") /*If operation equals "pause" or "play"*/ } ResponseDataResponseStatus is “ok”.

3.3.11 Participant Subscribes a Stream to WebRTC Endpoint

RequestName: “subscribe”

RequestData: The SubscriptionRequest object with following definition:

object(SubscriptionRequest):: { media: object(MediaSubOptions) }

object(MediaSubOptions):: { audio: object(AudioSubOptions) | false, video: object(VideoSubOptions) | false }

object(AudioSubOptions):: { from: string(StreamId) }

object(VideoSubOptions):: { from: string(StreamId), parameters: object(VideoParametersSpecification)/*If specific video parameters are wanted*/ | undefined/*If default video parameters are wanted*/, simulcastRid: string(rid) /* if simulcastRid is used, parameters will be ignored */ }

object(VideoParametersSpecification):: { resolution: object(Resolution) | undefined, framerate: number(WantedFrameRateFPS) | undefined, bitrate: number(WantedBitrateKbps) | string(WantedBitrateMultiple) | undefined, keyFrameInterval: number(WantedKeyFrameIntervalSecond) | undefined } ResponseData: The SubscriptionResult object with following definition if ResponseStatus is “ok”:

object(SubscriptionResult):: { id: string(SubscriptionId) }

3.3.12 Participant Stops a Self-Initiated Subscription

RequestName: “unsubscribe”

RequestData: The UnsubscriptionRequest object with following definition:

object(UnsubscriptionRequest):: { id: string(SubscriptionId) } ResponseData: undefined if ResponseStatus is “ok”.

3.3.13 Participant Controls a Self-Initiated Subscription

RequestName: “subscription-control”

RequestData: The SubscriptionControlInfo object with following definition:

object(SubscriptionControlInfo):: { id: string(SubscriptionId), operation: "update" | "pause" | "play", data: object(SubscriptionUpdate)/*If operation equals "update"*/ | ("audio" | "video" | "av")/*If operation equals "pause" or "play"*/ }

object(SubscriptionUpdate):: { audio: object(AudioUpdate) | undefined, video: object(VideoUpdate) | undefined }

object(AudioUpdate):: { from: string(StreamId) }

object(VideoUpdate):: { from: string(StreamId) | undefined, parameters: object(VideoParametersSpecification)/*If any video parameters are wanted to be re-specified*/ | undefined/*If the video parameters of the ongoing subscription are wanted to be kept*/ } ResponseData: undefined if ResponseStatus is “ok”.

3.3.14 Participant Sends Session Signaling

RequestName: “soac”

RequestData: The SOACMessage object with following definition:

object(SOACMessage):: { id: string(SessionId), /* StreamId returned in publishing or SubscriptionId returned in subscribing*/ signaling: object(OfferAnswer) | object(CandidateMessage) | object(RemovedCandidatesMessage) }

object(OfferAnswer):: { type: "offer" | "answer", sdp: string(SDP) }

object(CandidateMessage):: { type: "candidate", candidate: object(Candidate) }

object(RemovedCandidatesMessage):: { type: "removed-candidates", candidates: [ (object(Candidate) ] }

object(Candidate):: { sdpMid: string(mid), // optional in RemovedCandidatesMessage sdpMLineIndex: number(mLineIndex), // optional in RemovedCandidatesMessage candidate: string(candidateSdp) } ResponseData: undefined if ResponseStatus is “ok”.

3.3.15 Participant Receives Session Progress

NotificationName: “progress”

NotificationData: The SessionProgress object with following definition.

object(SessionProgress):: { id: string(SessionId), /* StreamId returned in publishing or SubscriptionId returned in subscribing*/ status: "soac" | "ready" | "error", data: object(OfferAnswer) | object(CandidateMessage)/*If status equals “soac”*/ | (undefined/*If status equals “ready” and session is NOT for recording*/ | object(RecorderInfo)/*If status equals “ready” and session is for recording*/ ) | string(Reason)/*If status equals “error”*/ }

object(RecorderInfo):: { host: string(HostnameOrIPOfRecorder), file: string(FullPathNameOfRecordedFile) }

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