When you switch from Remote Administration mode to Terminal
Server mode, you may not be able to use the Remote Assistance feature. When you
use a Remote Assistance request to invite someone to help you, the assistant
may not be able to connect to your computer. Then, the assistant receives the
following error message:
Remote Assistance failed
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This issue may occur in the following scenario:
| 1. | A server running Terminal Server Licensing is unavailable
when Terminal Server issues the Remote Assistance request. |
| 2. | The Remote Assistance request is used after Terminal Server
contacts a server running Terminal Server Licensing. |
The server running Terminal Server Licensing may be initially
unavailable when you switch from Remote Administration mode to Terminal Server
mode.
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To resolve the issue, restart the Terminal Server, and then
re-create the Remote Assistance request.
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Microsoft has confirmed that this is a bug in the Microsoft products that are
listed at the beginning of this article.
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Terminal Server uses a License Server to issue a Terminal
Services client license when you create a Remote Assistance request. Terminal
Server requests an X509 certificate from the License Server and uses it with
the Microsoft Remote Desktop Protocol (RDP) to encrypt communication between
Terminal Server and the Terminal Server client.
If a server running
Terminal Server Licensing is unavailable, Terminal Server uses a less secure
method. This method uses a public key to create a Remote Assistance request.
Terminal Server continues to try to register with a server running Terminal
Server Licensing until such a server is contacted.
When Terminal
Server contacts a server running Terminal Server Licensing, all existing Remote
Assistance requests that were created by using the public key become invalid.
Therefore, when you try to use the Remote Assistance request that was created
before Terminal Server has contacted the License Server, you may receive the
"Remote Assistance failed" error message.
For example, this issue may
occur in the following scenario:
| 1. | You switch from Remote Administration mode to Terminal
Server mode and then restart the computer. |
| 2. | You create a Remote Assistance request before the computer
has identified a server running Terminal Server Licensing. Terminal Server
issues the Remote Assistance request by using the less secure method (the
public key instead of the X509 certificate). |
| 3. | Terminal Server finds a License Server, and any subsequent
Remote Assistance requests are created with the X509 certificate. |
| 4. | The assistant tries to use the Remote Assistance request
(that was created without the X509 certificate) to connect to Terminal
Server. |
| 5. | The assistant receives the “Remote Assistance failed” error
message, because the Remote Assistance request that was created with the public
key is invalid. |
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