VNC^® Enterprise Edition User Guide

Bypassing the authentication rules

You can enable particular users to connect to VNC Server without specifying a password, bypassing VNC Server’s authentication mechanism altogether. You can:

•  Allow a user to connect as a Guest. See below for more information.

•  Establish a reverse connection to a client computer. See Establishing a reverse connection for more information.

Clearly, you should only allow trustworthy users to connect as Guests, and only establish reverse connections to client computers with trustworthy potential users. If you are setting up VNC Server on your own computer for remote access, note that a user must be present at the host computer for both these features to work.

Note: You can enable all users to connect without supplying a password if you consider it safe to do so. For more information, see Relaxing the authentication rules.

Allowing a Guest to connect

You can allow a particular user to connect as a Guest, bypassing the authentication mechanism specified by VNC Server. A Guest typically connects infrequently, or for a short period of time.

To connect a Guest, open the VNC Server Properties dialog. For more information on this dialog, see Using the VNC Server Properties dialog. On the Connections tab, select an alternative to the default None option from the Guest login access dropdown:

(Windows XP)

To grant to a connected Guest:

•  A Default set of VNC permissions, select Interactive.

•  A View Only set of VNC permissions, select View-only.

For more information on VNC permissions, see Restricting functionality for particular connected users. Note you cannot customize VNC permissions for Guests.

To enable a Guest to connect, a host computer user must turn on the Guest Login option on the VNC Server shortcut menu. For more information on this menu, see Using the VNC Server shortcut menu. For example:

(Windows XP)

Note: If the Guest Login menu option is turned off, Guests cannot connect. Note that connected users can turn this menu option on and off. When VNC Server starts, Guest Login is turned off by default.

When connecting to VNC Server, a Guest is presented with the VNC Authentication dialog:

(Windows XP)

To connect, the Guest must enter Guest in the Username field, and leave the Password field empty.

When the connection request is received by VNC Server, a connection prompt appears on the host computer:

(Windows XP)

A host computer user must approve the connection request within ten seconds or it will be automatically rejected. For more information on connection prompts, see Preventing particular users connecting.

Establishing a reverse connection

You may be able to establish a reverse connection to a particular client computer, bypassing the authentication mechanism specified by VNC Server.

Note: The client computer must be running Listening VNC Viewer. For more information, see Starting Listening VNC Viewer.

This feature might also be useful if the host computer is protected by a firewall that cannot be configured to allow incoming network communications, or by a router that cannot be configured to forward incoming network communications to the host computer, preventing normal connections. In a reverse connection, network communications from a host computer are outgoing.

To establish a reverse connection:

1. Open the VNC Server shortcut menu. For more on this menu, see Using the VNC Server shortcut menu:

(Windows XP)

2. Select Connect to Listening VNC Viewer. The Connect to Listening VNC Viewer dialog opens:

(Windows XP)

3. Enter the network address of the client computer (or a router) in the VNC Viewer field, for example 192.168.2.187, and click the OK button.

If you do not know a network address for the client computer, and it is also running VNC Server, you can ask a client computer user to follow the instructions in Step 2: Start VNC Viewer on the client computer. If not, you will need to ask the client computer user to use a command such as ipconfig (Windows) or ifconfig (Linux and Mac OS X).

Listening VNC Viewer listens for reverse connections on port 5500. If a reverse connection fails, it may be because the client computer is protected by a router and/or a firewall and these devices have not been configured to allow access to Listening VNC Viewer at port 5500. For more information on this, and connection issues in general, see Troubleshooting connection.

When a reverse connection is established, the desktop of the host computer is displayed on the client computer in exactly the same way as it is for VNC Viewer. A Listening VNC Viewer user controls the host computer in the same way a VNC Viewer user does. For more information, see Chapter 3, Using VNC Viewer.

A Full set of VNC permissions is granted to a Listening VNC Viewer user. For more information, see Restricting functionality for particular connected users. Note you cannot customize VNC permissions for Listening VNC Viewer users.