Invite a Participant to an Audio/Video Session
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After an audio/video session is created and related session events are registered, a Unified Communications Client API application invites a user to participate in the session. When the audio/video session is a peer-to-peer session involving another user, the remote participant is added using the SIP or TEL URI of the remote user. A TEL URI is used when the remote user joins the session using a telephone. In contrast, the remote participant SIP URI is a conference MCU URI when the audio/video session has been created to participate in a conference.
Using Unified Communications Client API, inviting a participant amounts to the following activities:
When a local client initiates a new video session, the client is responsible for creating the remote participant and associated media channels. Note that an incoming media session carries a fully configured remote participant complete with media channels. The local client does not add media channels to participants obtained from a session received in an invitation from a remote client.
- Creating a IUccSessionParticipant object by calling CreateParticipant on the session object.
- Calling QueryInterface on the participant object to get a IUccAudioVideoSessionParticipant interface. Audio/video channel functionality is available with this participant interface.
- Registering for appropriate events that can be raised by the IUccSessionParticipant and IUccAudioVideoSessionParticipant objects.
- Using the IUccAudioVideoSessionParticipant to create an audio channel connecting to the invited participant.
- Adding the audio channel to the IUccAudioVideoSessionParticipant object for the invited participant.
- Adding the participant object to the audio/video session.
Note
In Unified Communications Client API, making a computer-to-phone call follows the same programming pattern as making a computer-to-computer call. The caller must supply the SIP URI of the telephone to be called and must use audio-only media channel. The SIP URI format of a telephone is of the "sip:14255551111@sipserver.contoso.com".
The following C# code snippet illustrates this process.
IUccSession session;
string sipUri = "sip:jaya@contoso.com";
public void AddParticipant(string sipUri)
{
IUccSessionParticipant participant = null;
try
{
UccUri u = _UriManager.ParseUri(sipUri);
participant = this.session.CreateParticipant(u, null);
if (participant != null)
{
IUccAudioVideoSessionParticipant p = participant as IUccAudioVideoSessionParticipant;
IUccMediaChannel c = p.CreateChannel(
UCC_MEDIA_TYPES.UCCMT_AUDIO, null);
c.PreferredMedia = (int)(UCC_MEDIA_DIRECTIONS.UCCMD_RECEIVE | UCC_MEDIA_DIRECTIONS.UCCMD_SEND);
p.AddChannel(c);
this.session.AddParticipant(participant, null);
}
}
catch (COMException ex)
{
MessageBox.Show(ex.Message);
}
}
Attempts to add an audio channel on a computer without a sound card installed fails. After a participant is added to an AV session, by calling the AddParticipant method, the invited participant, if online, receives the invitation in a notification of the OnIncomingSession event. The AV session is established only after the invited participant accepts the invitation.