API Overview
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Unified Communications Client API is a SIP-based application framework for building and deploying real-time communications client applications against Microsoft Office Communications Server. In addition to standard features such as instant messaging, voice calling, video chatting, contact managing, and presence tracking, this framework allows the application to provide users with telephony integration, conferencing, encrypted audio/video calls, and publication and subscription of custom presence information and other application-specific data. The flexible publication and subscription framework makes the application framework appealing especially for developers who want to integrate presence information with line-of-business applications and to present the most relevant contact information in a particular application context.
Warning
The Unified Communications Client Platform (UCCP) API only supports the Single Threaded Apartment (STA) threading model. Do not use a multi-threaded model when developing a custom application using the UCCP API.
Unified Communications Client Application Architecture
Unified Communications Client API encapsulates two major functional features in real-time communications: signaling and media handling. The encapsulation of signaling provides a higher level object abstraction of an implementation based on the Session Initiation Protocol (SIP). The API also provides a set of signaling interfaces for developers interested in working at a lower SIP abstraction level. The encapsulation of media handling provides an object representation of an implementation of the Real-time Transport Protocol (RTP).
The Unified Communications Client API design separates the signaling and media handling between an application and the underlying SIP stack and media management over the RTP stack. The following diagram illustrates the Unified Communications Client API application architecture.
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The SIP stack handles signaling following the standard SIP. It is responsible for carrying out all low-level SIP operations, such as sending a session request, dispatching and receiving provisional responses, and accepting, forwarding, or rejecting an invitation. These operations are necessary for establishing communications and conference sessions where participants can communicate and collaborate with each other.
The media stack (Media Manager) is responsible for the low-level media management functions including establishing communication channels to transmit audio, video, or other application data between endpoints.
Unified Communications Client API exposes a set of COM-based API encapsulating the low-level functionalities and providing applications with SIP and media functionalities in object-oriented programming patterns. With Unified Communications Client API, developers can create unified multimodal communication applications, including instant messaging (IM), voice calling (computer-to-computer, computer-to-phone, and phone-to-phone), video chatting, application-sharing, and conferencing. It also works with Office Communications Server and other SIP registrar or proxy servers to manage presence information and facilitates communications among communication parties.