VNC^® Enterprise Edition User Guide

Configuring network communications

VNC Server listens for network communications—that is, for connection requests and for VNC Viewer for Java download requests—on one or more ports.

By default, two separate ports are assigned when VNC Server starts, one for connection and one for download requests. If available, then:

•  Under Windows and Mac OS X, VNC Server in both Service Mode and User Mode is assigned port 5900 for connection requests and port 5800 for download requests.

•  Under UNIX or Linux, VNC Server in:

— User Mode is assigned port 5900 for connection requests and port 5800 for download requests.

— The first instance of VNC Server in Virtual Mode is assigned port 5901 for connection requests and port 5801 for download requests. Subsequent instances of VNC Server in Virtual Mode are assigned port numbers incremented by one, where possible, for example 5902, 5903 (and 5802, 5803), and so on, up to the maximum number of desktops permitted by the host computer’s license.

Note: For more information about running multiple instances of VNC Server, and the different modes, see Running multiple instances of VNC Server.

If more than one instance of VNC Server is running on a host computer, they must all listen on different ports; see below for information on resolving port conflicts. Note, however, that a particular instance of VNC Server can listen on the same port for connection and download requests; see Making the connection and download port the same for more information.

Note: When connecting to VNC Server, a user must qualify the host computer’s network address with the port number in all cases except when VNC Server is listening for connection requests on port 5900 only. For more information, see Qualifying a network address with a port number.

Resolving port conflicts

VNC Server must listen for connection and for VNC Viewer for Java download requests on a unique port. This is one on which no other instance of VNC Server running on the host computer, or any other service or program, is listening.

Port conflicts disable VNC Server. You should be able to resolve them by changing the ports on which VNC Server listens. To do this, configure properties on the Connections tab of the VNC Server Properties dialog. For more information on this dialog, see Using the VNC Server Properties dialog.

(Windows XP)

Changing the connection port

You can change the port on which VNC Server is listening for connection requests. If you do this:

•  Users need to know the new port number (if it is not 5900) in order to enter it when connecting. For more information, see Qualifying a network address with a port number.

•  If the host computer is protected by a firewall, then the firewall must be configured to allow incoming network communications to the new port. For more information, see Allowing network communications through a firewall.

•  If the host computer is protected by a router and users will connect over the Internet, then the router must be configured to forward communications to the new port. For more information, see Configuring a router to forward network communications.

To change the port, enter a different number in the Accept connections on port field. Note that configuring this property does not affect currently connected users.

Changing the download port

You can change the port on which VNC Server is listening for VNC Viewer for Java download requests. If you do this:

•  Web browser users need to know the new port number in order to enter it when downloading. For more information, see Qualifying a network address with a port number.

•  If the host computer is protected by a firewall, then the firewall must be configured to allow incoming network communications to the new port. For more information, see Allowing network communications through a firewall.

•  If the host computer is protected by a router and web browser users will connect over the Internet, then the router must be configured to forward communications to the new port. For more information, see Configuring a router to forward network communications.

To change the port, enter a different number in the Serve Java viewer on port field. Note that configuring this property does not affect currently connected users.

Making the connection and download port the same

VNC Server can listen on the same port for connection and download requests. This may simplify firewall configuration and make the host computer more secure.

To use the same port, enter the same number in the Accept connections on port and Serve Java viewer on port fields. Note that configuring these properties does not affect currently connected users.