This article describes the contents of the Remote
Assistance invitation file that is sent from the Novice to the Expert. This
file is created when the Novice uses the Email
or Save invitation as a file
option in Remote
Assistance. This article does not address using Windows Messenger to establish
a Remote Assistance session.
For additional information about Remote Assistance,
click the article number below to view the article in the Microsoft Knowledge
Overview of Remote Assistance in Windows XP.
This article provides more in-depth information
about how Remote Assistance works and assumes that you, the reader, have a
general understanding of Remote Assistance as explained in the article Q300546.
The Remote Assistance Invitation file is written in
Extensible Markup Language (XML) and can be read and edited in a text editor
such as Notepad. Remote Assistance invitation files uses the following
In Windows XP, this extension is associated with Help and Support
Center. When the Expert executes the .MsRcIncident file, Windows starts Help
and Support, and then Help and Support passes the information to Remote
Assistance. Remote Assistance then parses the file and starts the process of
initiating a Remote Assistance session with the Novice computer that created
In this article, the terms ".MsRcIncident file" and "the
invitation" are used interchangeably. The term "ticket" refers to the record of
the invitation held on the Novice's computer.
The Novice computer has
a built-in local user account called HelpAssistant. This account is disabled by
default and has a randomly generated strong password. The account has limited
privileges and is used by the Expert to logon to the Novice computer during the
Remote Assistance session.
The Novice Invites the Expert to Connect to Their Computer
When the Novice's computer creates the invitation file, the
following actions occur:
- The HelpAssistant account is enabled.
- An entry in the Novice's table is created.
- The following information is obtained from the Novice's
computer: IP and computer name configuration information including requesting
port mapping from any Universal Plug-and-Play (UPnP) Network Address
Translation (NAT) servers on all interfaces on the Novice computer. If a UPnP
NAT server is present, it responds with its external IP address and a port
number reserved for the Novice computer. The UPnP NAT Server begins mapping
traffic on the IP:PORT to port 3389 on the NAT Client Novice computer.
The Expert Executes the Invitation File
The Expert executes the invitation file to start a Remote
Assistance session. On the Expert's computer a message is displayed inviting
the Expert to connect to the Novice's computer. Remote Assistance uses the
following information contained in the .MsRcIncident file to display this
The name to be used is contained in the USERNAME field
as in the example above where Kim Abercrombie is the name the Novice specified
when creating the invitation.Note
: When the Novice creates the invitation, Remote Assistance
pre-populates the Enter your name
box with the current profile name. The Novice may change this
To determine whether or not to prompt the Expert for a
password, Help and Support center looks at the RCTICKETENCRYPTED field. If it
set to "0", the Expert is not prompted for a password. If it is set to "1", the
Expert is prompted for a password. The password entered by the Expert is sent
to the Novice's computer.DTStart=="992646863" and DTLength="60"
Remote Assistance uses the DTStart and DTLength fields
to calculate the expiration time set by the Novice when the invitation is
: This time will be adjusted to the local time of the Expert
The expiration time as displayed to the Expert is only
informational. The Novice can cause the invitation to expire at any time by
in the View invitation status page in Help and Support Center.
This causes the ticket on the Novice computer to expire. Although the message
that is displayed to the Expert shows that the invitation is still open when a
connection is attempted, the Novice computer refuses the connection because the
ticket has expired.
If the Novice chooses to expire the ticket prior
to the invitation's preset time, the Experts invitation does not reflect this
change and the message displays the original expiration time that was set at
the invitations creation.
You may be concerned that the Expert could
"trick" the Novice computer by adjusting the time on the Expert computer;
however, this is not possible. To demonstrate this, refer to the following
If an invitation is created in Dallas with an
expiration time of 4:00 PM central time, and the Expert opens the invitation in
a location 1 hour behind Dallas time, such as Provo Utah, at 3:35 PM Provo time
(4:35 PM Dallas time) the message would show the ticket as expired because it
would be 4:35 PM in Dallas, and the Novice computer would have set the status
of the ticket to Expired.
If the Expert in Utah were to set the
system clock on their computer in such a way as to make the invitation message
appear as not expired on the Expert computer, the Expert would then be able to
attempt a connection to the Novice. When the Novice computer receives the
attempt it immediately declines to start a Remote Assistance session. There is
no user interaction required on the Novice's computer when this occurs.
Starting the Remote Assistance Session
When the Expert clicks the Yes
button, Remote Assistance calls Help and Support APIs to initiate
the session. Help and Support relies on Terminal Services to negotiate the
session. Help and Support Center pass the Remote Assistance invitation file to
Terminal Services uses the information it receives in the
RCTICKET field to negotiate a connection with Terminal Services on the Novice
The RCTICKET field contains a list of all IP addresses on
the Novice computer at the time of the invitations creation with a port number
in the format of IP:PORT.
Remote Assistance makes use of UPnP NAT
management, which enables Remote Assistance to work when the Remote Assistance
Novice is behind a UPnP-compliant NAT Device.
Windows XP Internet
Connection Sharing is the only NAT solution that is UPnP compliant.
: The following text is wrapped for reading purposes only.
: This is for version information and flags.18.104.22.168:3389;kim.redmond.microsoft.com:3389;10.0.0.5:3389
: This is a list of IP addresses and port numbers that were
present on the Novice computer at the time the Invitation File was
Terminal Services starts attempting connections with the
first interface in the list, 122.214.171.124:3389
in this case. If there is no response in 30 seconds, Terminal
Services moves to the next interface, kim.redmond.microsoft.com:3389
, and finally Terminal Services will try to connect to 10.0.0.5:3389
If this connection is not successful, Terminal
Services informs Help and Support Services, which in turn informs Remote
Assistance which generates the following message:
A Remote Assistance connection could not be established.
You may want to check for network issues or determine if the invitation expired
or was cancelled by the person who sent it.
Services on the Expert computer passes the credentials for the HelpAssistant
account to the GINA on the Novice's computer. If the credentials are accepted,
the Expert logs on to the Novice's computer using the HelpAssistant account.
Remote Assistance displays a message asking the Novice if they want to
start a Remote Assistance session with the Expert at that time. If the Novice
is logged on to multiple sessions, each session receives this
Before the Expert is allowed to connect to the Novice
computer, the Group Policy Settings are checked. If the Policies do not allow
the Novice to receive Remote Assistance the connection is refused.
the credentials are met the Remote Assistance session is established using the
RDP protocol and Port 3389 through Terminal Services on the Novice and Expert
At this point the Expert can only see the Novice's
desktop. The Expert must request to take control of the Novice's computer and
the Novice must allow control by clicking yes to the corresponding prompt. If
the Novice wants to take back control at any time during the session, the ESC
key can be pressed.
When the Ticket Expires
Remote Assistance maintains a table of all open tickets in
hive of the registry. When there are no open tickets, Remote
Assistance disables the HelpAssistant account and removes the Allow logon
through Terminal Services right in one hour. Remote Assistance also turns off
any port mapping on UPnP-compliant NAT devices.
The ticket expires
automatically when the time limit has expired. A user that is a member of the
Owner or Administrator group on the Novice computer can also cause the ticket
to expire at anytime by performing the following steps:
- Click Start, and then click Help and Support.
- Click the Remote Assistance link.
- Click the View invitation status link.
- Select the desired open ticket to expire.
- Click the Expire button.
When a ticket is in the expired state, any invitation files
that is used to connect to the Novice computer fails and there is no message or
logging to inform the Novice that Remote Assistance has declined an expired