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How Remote Assistance Works In Windows XP?


The two parties in a Remote Assistance session are called the beginner and the specialist. To use Remote Assistance, both parties must be using Windows XP, both must have active Internet connections or be on the similar local area network, and no one can be blocked by firewalls.

Creating a complete Remote Assistance session is a three-step process:

1. The novice sends a Remote Assistance invitation, typically using Windows Messenger or e-mail.

2. The expert accepts the invitation, opening a terminal window that displays the desktop of the novice’s machine.

3. The expert views the desktop in a read-only window and exchanges messages with the beginner using text or voice chat. Before the expert can work with objects on the remote PC, the beginner must enable the Allow Expert Interaction option.

At the heart of each Remote Assistance connection is a small text file called an RA ticket. (More officially, its type is Microsoft Remote Assistance Incident and its extension is .msrcincident.) This file uses XML fields to define the parameters of a Remote Assistance connection. When you use Windows Messenger to manage the connection, the RA ticket is not at all visible. When a novice sends a Remote Assistance ask for via e-mail, however, the RA ticket rides along as an attachment to the message. The expert has to double-click this file to launch the Remote Assistance session.

Remote Assistance works by making a direct connection among two computers using the TCP/IP protocol. For this connection to be booming, both computers involved must be capable to communicate using their respective IP addresses.

A Remote Assistance connection is comparatively easy when both parties have public IP addresses gives by an Internet service provider. In that scenario, the computers connect directly, sending and receiving data on TCP port 3389. Routers along the Internet connection between the two computers are able to recognize the addresses of the two computers and send the respective packets to their correct destinations. Internet Connection Firewall in Windows XP mechanically opens this port when you request a Remote Assistance connection.

Remote Assistance connections are also simple and normally trouble-free on a private network, such as a workgroup in a home or small office. In that case, each machine can communicate directly with the other without having to pass through any routers.

What happens if one or both sides of the connection are using private IP addresses allocated through Network Address Translation (NAT)? That’s when Remote Assistance gets complicated. Because these addresses are reserved for exclusive use on private networks, they cannot be routed over the Internet. Instead, a software or hardware-based NAT device handles the sound work of passing data between the single public IP address it uses to communicate with the Internet and the private IP addresses on the local network. How it performs that job decide whether the Remote Assistance connection will succeed or fail.

The exact outcome depends on how the computer acquired the private IP address:

Internet Connection Sharing: When you use Internet Connection Sharing (ICS) from Windows XP or Windows Me, the ICS server hands out private IP addresses to all other computers on the network. The ICS server listens for Remote Assistance traffic on TCP port 5001 and sands it to port 3389, permitting the connection to be victorious on its end, in spite of whether the question in computer is playing the role of beginner or expert. If computers on both ends of the connection are using any combine of public IP addresses and private addresses supplied by ICS, the Remote Assistance session should work completely.

UPnP-compatible hardware router or residential gateway: If the source of a private IP address is a hardware router or housing gateway, the connection will be successful if the router supports the Universal Plug and Play (UPnP) standard. Most routers manufactured in 2001 or previous do not support UPnP, even though a firmware upgrade might add this capability.

Non-UPnP-compatible hardware router or residential gateway: If both computers are at the back NAT devices that are not UPnP well-matched, it is not possible to total Remote Assistance connection. If only one computer is using a private IP address whose source is a hardware router or residential gateway that is not UPnP well-matched, making a successful connection is frequently possible, although it needs jumping through some hoops. In this configuration, your best bet is to use Windows Messenger to create the Remote Assistance connection. The beginner starting the connection to the expert on a random port; the expert then uses this port to initiate a connection back to the novice.

The trickiest connection of all involve a beginner who is behind a non-UPnP NAT device, such as a router or residential gateway on a cable or DSL connection, and who is not capable or unwilling to use Windows Messenger. In that case, you may be able to make a Remote Assistance connection work by editing the RA ticket file. Find the address of the NAT device (the public IP address it uses to connect to the Internet) and the private address of the beginners computer;

Then follow these steps:

1. On the NAT device attached to the novice’s network, open port 3389. Traffic on this port should be able to reach the beginner machine before it can complete the Remote Assistance connection. In the popular Linksys router product family, for example, you achieve this goal by using the Forwarding option in the router’s Control Panel.

2. Open the Help And Support Center and create a Remote Assistance invitation, saving it as a file on your desktop or in one more suitable location. This ticket file contains a pointer to your private IP address; if the beginner sends this ticket to an expert who is not on the same private network as you, it will fail because the beginner computer will not be able to find a route to the expert’s IP address.

3. Open Notepad or one more text editor and edit the RCTICKET field, adding the outdoor IP address of the NAT device before the internal IP address. For example, if your NAT device uses an outside IP address of 24.100.255.255 and your private IP address is 192.168.1.105 and your machine name is Groucho.

RCTICKET="65538,1,24.100.255.255:3389;192.168.1.10 5:3389;groucho:3389, encrypted connection info

4. Send the RA ticket file to the specialist. When he or she double-clicks this file, the information you added will permit the file to work its way over the Internet to your NAT device and then into your computer on port 3389.