[This is preliminary documentation and is subject to change.]
A custom Microsoft Lync 2013 Preview SDK client relies upon the client process running within Microsoft Lync 2013 Preview. If Lync 2013 Preview is not running on your client, the client cannot obtain an instance of the LyncClient class. When a user signs in to Microsoft Lync Server 2013 Preview using the custom client, it is actually causing the Lync 2013 Preview client process to issue the sign-in request to Lync Server 2013 Preview on behalf of the user.
Lync 2013 Preview can support multiple instances of a custom client running on one computer with some restrictions.
A user can only attempt to sign in to Lync Server 2013 Preview from one client.
Once a user is signed in using a custom Lync SDK application or Lync 2013 Preview, other clients must use the established communication session.
If a user signs in to Lync Server 2013 Preview from a custom Lync SDK client, Lync 2013 Preview uses the newly established session to update its UI as though a user had signed in from the Lync 2013 Preview client.
You can suppress the Lync 2013 Preview UI so a user only experiences the UI presented by your custom Lync SDK client. The custom Lync SDK client continues to use the client process that underlies the Lync 2013 Preview UI.
Multiple instances of a custom Lync SDK client can run concurrently. If a user is signed in to Lync Server 2013 Preview using Lync 2013 Preview, your custom Lync SDK client must not attempt to sign in again. However, each instance of your custom Lync SDK client still has access to the client process running within Lync 2013 Preview.
The following illustration shows the relationship between collaboration processes running on a local client that hosts your application.