Building Real-Time Communication Apps Using Microsoft UCMA 4.0 SDK

Building Real-Time Communication Apps Using Microsoft UCMA 4.0 SDK

Microsoft’s Unified Communications Managed API (UCMA) 4.0 SDK provides a managed-code platform for building server-side real‑time communications applications that integrate voice, video, instant messaging, presence, and conferencing with Lync/Skype for Business Server. This article walks through core concepts, architecture, typical application scenarios, and a step‑by‑step example to get a simple real‑time communication service up and running.

What UCMA 4.0 provides

• Server-side API: Managed .NET libraries for building trusted applications running on application servers.
• Communication modalities: Instant messaging (IM), presence, audio/video, conferencing, telephony/media control.
• Integration points: SIP-based signaling, Microsoft conferencing, and media platform for call control and media processing.
• Scalability & trust model: Applications can be trusted by the server (trusted application model) for higher privileges and scale.

Typical use cases

• Auto-attendants / call routing and IVR
• Conferencing bots that join and manage meetings
• Contact center back-ends and call recording
• Presence-aware notification and workflow integrations
• Real‑time translation/transcription services

Architecture and core components

• Endpoint types
  • ApplicationEndpoint: Represents a user-like endpoint for trusted server apps.
  • UserEndpoint: Represents an actual user account.
• Platform class: Central lifecycle manager that connects your app to the server topology and provides access to settings and resources.
• Conversations and modalities: Conversation object models participants and modalities (InstantMessagingFlow, AudioVideoCall, VideoFlow).
• Call and media handling: AudioVideoCall and AudioVideoFlow for establishing and controlling calls, media streaming, DTMF, recording.
• Automatic management features: Reconnection logic, keepalives, failover patterns provided by UCMA runtime.

Prerequisites

• Windows Server (supported versions per UCMA 4.0 documentation)
• Microsoft Lync or Skype for Business Server (matching supported versions)
• Visual Studio with .NET Framework matching UCMA assemblies
• UCMA 4.0 SDK installed on development machine
• Trusted application registration in Topology Builder (or appropriate server configuration)

Development workflow — step-by-step example

Below is a concise walkthrough to build a simple application that accepts an incoming audio call and plays a greeting.

1. Project setup

   • Create a new C# Console Application targeting the supported .NET Framework.
   • Reference UCMA 4.0 assemblies (Microsoft.Rtc.Collaboration.dll, Microsoft.Rtc.Collaboration.AudioVideo.dll, etc.).
   • Ensure the server-side application pool and account are configured and trusted in the Skype for Business/Lync topology.

2. Initialize the CollaborationPlatform

   • Instantiate CollaborationPlatform with a LocalEndpointSettings or ApplicationPlatformSettings and start it.
   • Register event handlers for platform state changes and shutdown.

3. Create and establish an ApplicationEndpoint

   • Create an ApplicationEndpoint using the CollaborationPlatform and an endpoint configuration (SIP URI and deployment settings).
   • Call Establish() on the ApplicationEndpoint to register with the server.

4. Listen for incoming calls

   • Subscribe to the ApplicationEndpoint’s AudioVideoCallReceived event.
   • In the event handler, accept the incoming call by calling audioVideoCall.AcceptAsync().

5. Play greeting and manage the call

   • Once the call is established, create an AudioVideoFlow or use the call’s Connect/Start APIs.
   • Use the MediaController or ToneController as needed to play a WAV prompt or media file. Example pattern:
     • Create a Prompt to play audio from a file stream.
     • Use the AudioVideoFlow to send the prompt to the remote party.
   • Handle call termination and cleanup on AudioVideoCall.StateChanged or CallEnded events.

6. Clean shutdown

   • Properly dispose of endpoints and stop the CollaborationPlatform to release resources and unregister the application.

Example (pseudocode)

”` using Microsoft.Rtc.Collaboration; using Microsoft.Rtc.Collaboration.AudioVideo;

Start platform; Create ApplicationEndpoint; endpoint.Establish();

endpoint.AudioVideoCallReceived += (s