VNC^® Enterprise Edition User Guide

Troubleshooting connection

The following sections provide additional information to help you connect.

If after reading this you still cannot connect, or if you want more information, consult the RealVNC web site, or contact Support. For details of these resources, see About This Guide.

If all else fails, and providing a host computer user is present, you can ask that person to connect to you. For more information, see Establishing a reverse connection.

Connecting within a private network

If both client and host computers are managed within a closed network environment such as a Local Area Network (LAN) or Virtual Private Network (VPN), you are connecting within a private network. This is common in corporate and other enterprise environments, and may also be the case if you are connecting two computers at home.

To connect within a private network, enter the network address of the host computer itself in the VNC Viewer: New Connection dialog, for example:

(Windows XP)

If you do not know the network address of the host computer:

•  And you do not have access to it, you will need to consult your system administrator or a host computer user.

•  And you do have access to it, follow the appropriate instructions for the host computer’s platform below.

Windows

To discover the network address of a host computer, hover the mouse over the VNC Server icon in the Notification area. A tooltip containing a network address appears:

(Windows XP)

UNIX or Linux

To discover the network address of a host computer, hover the mouse over the VNC Server icon in the Notification Area. A tooltip containing a network address appears:

(Ubuntu 8.10 Linux)

Note: Under some versions of UNIX, a VNC Server icon is not available. You will have to use system tools to discover the network address.

Mac OS X

To discover the network address of a host computer, hover the mouse over the VNC Server icon in the Status Bar. A tooltip containing a network address appears:

(Mac OS X 10.5)

Connecting over the Internet

If you are connecting over the Internet, for example to friends and family, or in to the office on the move, it is likely that the host computer will be protected by a router or similar device acting as a communication gateway and public interface.

To connect over the Internet, you must enter the network address of the router in the VNC Viewer: New Connection dialog, for example:

(Windows XP)

If you do not know the network address of a host computer’s router:

•  And you do not have access to the host computer, you will need to ask a host computer user to follow the instructions below, or to use a service such as www.whatismyip.com.

•  And you do have access to the host computer, follow the instructions below.

To discover the network address of a router:

1. Open the VNC Server Status dialog.

2. In the Details area, click the [test] link:

The VNC Server Connection Test dialog appears.

3. Click the Start button. RealVNC attempts to contact the host computer over the Internet. Providing the host computer is connected to the Internet, the network address of an intermediary device is revealed:

(Windows XP)

Configuring a router to forward network communications

In a typical home or small office environment, a router assigns a private network address to an internal computer. You should also be aware that VNC Server listens for network communications on a particular port. The router must be configured to forward communications from VNC Viewer to the correct port at the correct private network address. This procedure is known as port forwarding.

Note: Port forwarding instructions are specific to routers. If you do not have access to the host computer, ask a host computer user to consult the manufacturer’s documentation, or visit www.portforward.com.

Note that a router may act as a public interface to more than one computer in a home or small office environment. If you want to connect to multiple host computers, then VNC Server must be running on each and listening on a different port. The router must be configured to distinguish between host computers using port numbers.

Consider the following example:

A.  Router with a network address assigned by an ISP, for example 82.2.12.81.   B.  Host computer with a network address assigned by the router, for example 192.168.0.1. VNC Server is listening on the default port, 5900.   C.  Host computer with a network address assigned by the router, for example 192.168.0.2. VNC Server has been configured to listen on port 5901.   D.  The Internet.

In this scenario, the router must be configured to forward port 5900 to host computer B at 192.168.0.1 and port 5901 to host computer C at 192.168.0.2.

When you connect to either host computer from VNC Viewer, you must enter the network address of the router: 82.2.12.81. In addition, to connect to host computer C, you must qualify the router’s network address with the port number: 82.2.12.81:1. To find out why this is, see Qualifying a network address with a port number.

Qualifying a network address with a port number

VNC Server listens for network communications on a particular port. By default, and providing it is available when VNC Server starts, this is port 5900 for connection requests. This port is registered for use by VNC Server with the Internet Assigned Numbers Authority (IANA).

Note: For more information on ports, see Configuring network communications.

If VNC Server is listening on any other port, you must qualify the network address of the host computer (or router) with the port number when you connect from VNC Viewer, for example:

(Windows XP)

If you know that VNC Server is listening on a port between 5901 and 5999, append a colon (:) and an identifying number (1 through 99) to the network address, for example:

johndoe:1
192.168.2.187:1
[2001:db8::1]:1

If you know that VNC Server is listening on any other port, append a double colon (::) and the full port number to the network address, for example:

johndoe::6001
192.168.2.187::6001
[2001:db8::1]::6001

If you do not know on which port VNC Server is listening:

•  And you do not have access to the host computer, you will need to consult your system administrator or a host computer user.

•  And you do have access to the host computer, follow the appropriate instructions for its platform below.

Windows

To see whether VNC Server is listening on a port other than 5900, double-click the VNC Server icon in the Notification area to open the VNC Server Status dialog. If applicable, this information is appended to the network address in the Details area:

In this example, VNC Server is running on host computer 192.168.2.133 and listening on port 80.

Unix or Linux

To see whether VNC Server is listening on a port other than 5900, click the VNC Server icon in the Notification Area to open the VNC Server Status dialog. If applicable, this information is appended to the network address in the Details area:

In this example, VNC Server is running on host computer 192.168.2.187 and listening on port 5901.

Mac OS X

To see whether VNC Server is listening on a port other than 5900, click the VNC Server icon and, from the shortcut menu, select Status to open the VNC Server Status dialog. If applicable, this information is appended to the network address in the Details area:

In this example, VNC Server is running on host computer 192.168.2.168 and listening on port 6001.

Allowing network communications through a firewall

If the host computer is protected by a firewall, then the firewall must be configured to allow incoming network communications to the port on which VNC Server is listening. To find out which port this is, see Qualifying a network address with a port number.

The firewall might be automatically configured by the operating system of the host computer. If not, you will probably see the following error message when you connect from VNC Viewer:

The instructions for adding exceptions for ports are specific to firewalls. If you do not have access to the host computer, ask a host computer user to consult the manufacturer’s documentation.

Miscellaneous connection messages

This section explains various error or warning messages you might see.

Failing to authenticate correctly

If you see the following warning message:

then you have not authenticated yourself correctly to VNC Server. Note that user names and passwords are case-sensitive. Click the Yes button to try again up to four more times.

If you do not know the correct user name or password, and you do not have access to the host computer, you will need to consult your system administrator or a host computer user. If you do have access to the host computer, and sufficient privileges to configure VNC Server, you may be able to relax the authentication rules. For more information, see Relaxing the authentication rules.

Failing to authenticate as ‘you’

If you see the following warning message:

then VNC Server has been configured to authenticate a VNC Viewer user with the credentials used for logging on to the operating system of the host computer. Your user name and password for logging on to the host computer, however, have not been added to the authentication list.

If this is the case and you do not have access to the host computer, you will need to consult your system administrator or a host computer user. If you do have access to the host computer, and sufficient privileges to configure VNC Server, you may be able to register your credentials. For more information, see Managing users and groups in the authentication list.

Connecting from an unauthorized computer

If you see the following error message:

then it could be that VNC Server has been configured to prevent connections from the client computer you are using.

If this is the case and you do not have access to the host computer, you will need to consult your system administrator or a host computer user. If you do have access to the host computer, and sufficient privileges to configure VNC Server, you may be able to unblock your client computer. For more information, see Preventing connections from particular client computers.

Alternatively, you may be able to connect from a different client computer.

Being rejected by a host computer user

If you see the following warning message:

then VNC Server has been configured to display connection prompts to a host computer user, and your request has either been explicitly rejected, or has timed out (this could either be because the prompt was deliberately ignored, or because no host computer user is actually present).

If this is the case and you do not have access to the host computer, you will need to consult your system administrator or a host computer user. If you do have access to the host computer, and sufficient privileges to configure VNC Server, you may be able to bypass host computer connection prompts. For more information, see Preventing particular users connecting.