Session Signaling
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Unified Communications Client API sessions use an underlying SIP layer to handle communications between the endpoints in the session. This is true with Focus-based conference sessions and media sessions. Each session type defines a specific mode of communication. The IM session interface provides methods to send text. Audio/video-related interfaces provide functionality to send and receive media streams. Application sessions permit sharing of desktop applications with remote clients.
The IUccSignalingChannel and related interfaces provide methods and properties to formulate your own SIP messages. These custom messages can be sent in the same session.
A good example of this scenario involves the participants in an IM session. The IM session is designed to send text messages between the participants using the SendMessage method. Using this method, a participant can send and receive text from other participants. If a participant wants to send a file to another participant, the signaling channel interface lets a user send something like a document or an image file to another user within the context of the session. The transmitted document is packaged as an XML blob in the body of the message. The signaling channel event, OnIncomingMessage, allows the recipient of the file to persist it in a file stream and use the received signaling channel to send data to the message originator.