Mirar el cine-ensayo

Windows XP’s Remote Assistance feature enables you to ask another Windows XP user for help with your computer or to provide help to another user. To request help, you can start Remote Assistance from

the Help and Support menu: Click Invite a Friend to Help You with Remote Assistance,, followed by Invite Someone to Help You. Both computers must be running Windows XP and Windows Messenger.

FIGURE 2.30

Running CHKDSK from the Windows desktop.

CHKDSK options

Starts CHKDSK

Click Yes to schedule repair if Automatically fix file system errors is selected on the system drive

You can get help from your Windows Messenger (WM) buddy list or by sending an email to other Windows users (see Figure 2.31).

FIGURE 2.31

Preparing to invite another user to help you with Remote Assistance.

Click Sign In if you want to invite someone on your Windows Messenger (WM) buddy list who is currently online (if you’re not already online). If you’re already online with WM, click the icon for a buddy list member who can help you, then click Invite This Person. You can even ask for help from the WM interface: Click I Want To…, More, and Ask for Remote Assistance. Select the user from the list to send the invitation.

If all your WM buddies who can help you are offline, type an email address or click the address book icon to select an address, and then click Invite This Person.

If you send an email message, specify a maximum length of time for the invitation to be valid (one hour is the default); this helps to pre- vent unauthorized users from hacking your system (you are, after all, allowing complete access to your PC from a remote computer). You are strongly encouraged, although not required, to set up a password for your helper to use. You must provide the password to the user separately; I recommend that you agree on a password in advance, or call your helper by phone to communicate the password.

In either case, once the invitation/offer to help has been sent, the WM Conversation box appears on both sides of the connection. The user who requested help is called the Novice, and the helper is called the Expert. The Expert can click Accept (Alt+A) to start the help process, or Decline (Alt+D) to reject the request for assistance. A sim- ilar screen on the Novice side allows the user who asked for help to cancel the request if desired.

During the Remote Assistance process, the Novice controls the process; the Novice must specifically grant permission for the Expert to view the screen and use text chat. A two-column toolbar appears on the Novice’s screen during the entire help process; the left column is used for displaying both sides’ chat messages; the lower-left corner provides a message-entry area. The right column contains controls for file transfer, audio chat and quality settings, disconnecting, and stop control, as shown in Figure 2.32.

Figure 2.33 shows the Expert’s view of the requester’s screen. The left side shows the chat process, with the lower-left corner used for message entry. The larger window shows a scaled or scrollable actual- size view of the requester’s display.

FIGURE 2.32

The Novice’s control panel during a typical Remote Assistance session.

FIGURE 2.33

The Expert’s control panel during a typical Remote Assistance session. Note the chat window indicates that the Expert has taken control of the system.

Expert's Chat window

Release/Take Control toggle button

Until the Expert clicks the Take Control button, the Novice controls the system; as before, the Novice must specifically permit this to take place. This enables the Expert to watch the Novice try a process, or allow the Expert to take over if necessary. During the process, either side can initiate a file transfer and start or stop voice chat to help solve the problem.

Whenever desired, the Novice can press Esc to stop remote control of the system. Either side can click Disconnect to stop the process. Troubleshooting Remote Assistance

If you can’t make a connection with Remote Assistance, check to see how both sides are connected to the Internet.

Check the following:

• If both the Novice’s and Expert’s computers are connected to a type of router that uses a feature called Network Address Translation (NAT) but doesn’t support Universal Plug and Play (UPnP), the computers can’t connect to each other (check your router’s documentation).

• You need to configure your firewall software and your NAT router to allow traffic on TCP port 3389 (the port used by the Remote Desktop Protocol). Check your firewall appliance, firewall soft- ware, or router documentation for details.

If your router supports UPnP, but Windows XP doesn’t have UPnP installed, and you can’t set up a Remote Assistance connection, you need to install UPnP. Follow these steps:

1. Open the Add/Remove Programs icon in Control Panel.

2. Click Add/Remove Windows Components.

3. Scroll down to Networking Services and select it.

4. Click Details.

5. Click Universal Plug and Play.

6. Click OK to install it.

Securing UPnP on Windows XP

Installing UPnP on a Windows XP system that is not running Service Pack 2 or greater creates a significant security risk, described in detail in Microsoft Knowledge Base article 315000.

To prevent UPnP from becoming a way for hostile remote users to take control of your computer, upgrade to Service Pack 2 if your system is still running the original release or Service Pack 1. If this is not possi- ble, install the patch referred to in Microsoft Security Bulletin MS01- 059, “Unchecked Buffer in Universal Plug and Play Can Lead to System Compromise.” You can download this patch through Windows Update for Windows XP, or directly from this URL:

http://www.microsoft.com/Downloads/Release.asp?ReleaseID=34951 By default, a patched machine will search only the same subnet or a pri- vate IP address for UPnP device descriptions, and only up to four router hops.