Archived from groups: microsoft.public.windowsxp.work_remotely (
More info?)
clint <clint@discussions.microsoft.com> wrote:
> I get an error that reads:
> Remote Assistance connection could not be established because the
> remote host name could not be resolved
>
> I working behind DSL Modem/Router combo and on the other end we have
> a cable modem/router combo.
The problem is with the NAT router at the "Novice" end (the person who
requests the assistance).
It is not a problem for the "Expert" (the person responding to assistance
requests) to be behind a NAT router.
At the Novice end, any NAT router in use must support UPnP, and UPnP must be
specifically enabled in the router configuration. At the Novice end, XP
must have the SSDP Discovery Service running (this is the default, but
sometimes this service is mistakenly disabled by users), and must have
Windows Firewall configured to make Exceptions for "UPnP Framework", for
"Remote Assistance", (and possibly also for "Remote Desktop"). In these
circumstances, Remote Assistance will automatically work, and you will not
get the error you report.
If the Novice's NAT router does not support UPnP, then you will never get
Remote Assistance to work automatically. UPnP is required in the NAT router
so that Remote Assistance can discover the WAN IP address of the Novice's
internet connection, to be written into the help request ticket.
If you wish to make Remote Assistance work through a NAT router at the
Novice end which does not support UPnP, then you must be prepared to take
special manual steps:
1. The Novice's NAT router must be configured to forward TCP port 3389 to
the LAN IP address of the PC requesting assistance;
2. The Novice's Remote Assistance requests must be sent via e-mail or file
transfer, not by Messenger;
3. The Expert must have a means of knowing the WAN IP address of the
Novice's internet connection (i.e. the WAN IP address of the Novice's NAT
router);
4. Every time the Expert receives an Remote Assistance request ticket from
this Novice by e-mail or file transfer, the Expert must not open it
immediately. Instead, the Expert should open the ticket in Notepad, and
edit the obvious incorrect IP addresses in the ticket (which will have a
":3389" port designator suffix) to change the IP address to the known WAN IP
address of the Novice's internet connection, still with the ":3389" suffix.
Then the Expert should save the changes, and then double-click on the ticket
icon so as to open the Remote Assistance session.
Steps 1-4 are unnnecessary if the Novice's NAT router supports UPnP.
--
Robin Walker
rdhw@cam.ac.uk
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