Remote Desktop Works, Remote Assistance Doesn't

[Sid Joyner]

Hi All:

I am trying to assist a friend remotely on his computer. He is running
Windows XP Media Center Edition SP2 with all the Windows updates. (It's a
relatively new computer.) He is also behind a router and is using Norton
Systemworks 2005 firewall. I have port 3389 forwarded on the router to his
computer.

I can use Remote Desktop and connect to his user login remotely. No problem.

However, when I reply to a Remote Assistance invitation he sends, it appears
to fire up the HelpAssistant module, but he immediately gets a "Remote
Assistance failed. Please Try Again. " dialog box on his end. Then I get a
message telling me that he denied my request.

I have checked that Remote Assistance is enabled both on the Systems/Remote
dialog box and the Group Policy/Local Computer Policy/Admin Templates/Remote
Assistance dialog on his computer. In addition, I added a registry entry
called AllowTSConnections that I found in the following Microsoft Kbase
article: http://support.microsoft.com/?kbid=305608. I also notice that the
invitations sent to me from his computer have just the local IP address
(192.168.x.x) and not the real IP address; I have to edit the invite by
hand. I thought that had been fixed by Microsoft somewhere down the line as
I usually get both the IP and local IP embedded in an invite now from other
people I assist who are behind routers.

Still, no luck. I find it interesting that Remote Desktop works and Remote
Assistance seems to connect but something automatically denies the request
immediately on his installation.

Any ideas? Thanks a lot as I want to use this as a training tool. Hopefully
someone can help me with this problem. Thanks in advance.

 

[Robin Walker [MVP]]

I also notice that the
invitations sent to me from his computer have just the local IP
address (192.168.x.x) and not the real IP address; I have to edit the
invite by hand. I thought that had been fixed by Microsoft somewhere
down the line as I usually get both the IP and local IP embedded in
an invite now from other people I assist who are behind routers.

For Remote Assistance to work when the Novice is behind a NAT router or
firewall, then all of the following must be true:

1. The NAT router must support UPnP and have UPnP enabled and working.
2. The software firewall must have Exceptions defined to allow incoming
calls on:
TCP port 3389 (Remote Desktop and Remote Assistance)
TCP port 2869 (UPnP)
UDP port 1900 (UPnP)
3. The software firewall must allow C:\Windows\system32\sessmgr.exe to act
as a server, able to open any ports.
4. Windows service "SSDP Discovery Service" must be running.

For Remote Assistance, there is no need to configure port-forwards in the
NAT router, as it will set up the required port mappings by UPnP at runtime.