VNC^® Enterprise Edition User Guide

Running multiple instances of VNC Server

Under any platform, and providing you have a license to do so, you can run more than one instance of VNC Server on a host computer.

This powerful feature means you can set up the host computer so users can connect to it in different ways. For example, you could set up one instance of VNC Server so that connections to it are optimized for speed, and another so connections are optimized for security. VNC Server facilitates this using modes, each of which permits a different level of access to the host computer.

Note: To see how to start VNC Server in different modes, read Starting VNC Server.

To find out more, read the section appropriate to the platform of the host computer below.

Windows

Under Windows, a host computer user with administrative privileges can start VNC Server in Service Mode. This means VNC Server runs, and users can connect, irrespective of whether or not a host computer user is currently logged on. By default, connecting users must know the user name and password of a member of the Administrators group in order to connect. In addition, by default, VNC Server starts in Service Mode automatically when the host computer is powered on.

In addition, or alternatively, a host computer user can log on and start VNC Server in User Mode. This means VNC Server runs, and users can connect, just while this host computer user is logged on. (Connections are terminated on log off.) By default, connecting users must know either the user name and password of the currently logged on host computer user or of a member of the Administrators group in order to connect.

Once connected to VNC Server in either mode, a connected user has the same privileges (that is, access rights) on the host computer as the currently logged on host computer user. For more information, see Authenticating connections to VNC Server.

Because only one host computer user can log on to a Windows computer at a time, this means a maximum of two instances of VNC Server can run concurrently on a Windows host computer – one in Service Mode, and one in User Mode for the currently logged on host computer user. Both instances must listen on different ports; see Configuring network communications for more information.

UNIX or Linux

Under UNIX or Linux, a host computer user can log on and start VNC Server in User Mode. In this mode, VNC Server runs attached to the console X Server session, which means that:

•  A VNC Server icon and VNC Server Status dialog can be displayed in order to help the host computer user configure VNC Server after it has started, if necessary.

•  Connected users can access applications currently running on the host computer.

•  VNC Server stops, and all connections are terminated, when the host computer user starting VNC Server logs off.

•  By default, users must know the user name and password of the host computer user starting VNC Server in order to connect. Once connected, they have the same privileges (that is, access rights) as this host computer user. For more information on privileges, see Authenticating connections to VNC Server.

Depending on the terms of the license, a host computer user can also, or alternatively, log on and start VNC Server in Virtual Mode. In this mode, VNC Server runs attached to a new virtual desktop, detached from the monitor and independent of the console, which means that:

•  No VNC Server icon or VNC Server Status dialog can be displayed in order to help the host computer user configure VNC Server after it has started. To see how to work with VNC Server in this mode, read Working with VNC Server in Virtual Mode (UNIX or Linux only).

•  Connected users cannot access applications currently running on the console of the host computer. Instead, an isolated workspace is provided. Note this powerful feature can help prevent conflicts; each user can be directed to connect to their own instance of VNC Server in Virtual Mode, and control a (virtual) desktop independently.

•  VNC Server does not stop when the host computer user logs off. Connected users stay connected, and new users can connect. VNC Server must be explicitly stopped.

•  By default, users must know the user name and password of the host computer user starting VNC Server in order to connect. Once connected, they have the same privileges (that is, access rights) as this host computer user. For more information on privileges, see Authenticating connections to VNC Server.

Under UNIX or Linux, more than one host computer user can log on at a time. Each currently logged on host computer user can start VNC Server in Virtual Mode, and all instances, for all users, run concurrently. Note that all instances, in either mode, must listen on different ports; see Configuring network communications for more information.

VNC Server can run as many times as the host computer’s license permits. Each time a host computer user starts VNC Server (whether in User Mode or in Virtual Mode), the count of the remaining permitted desktops (that is, instances of VNC Server) is decremented. To see how many desktops are left, type vnclicense -check at the command line. For example, the message:

means that five VNC Server desktops are licensed to run concurrently on this host computer, and three are already running: two started by John Doe, and one by Jane Doe. Two are left to run.

Note: You can release licenses by killing desktops. To see how to do this, read Stopping VNC Server.

Mac OS X

Under Mac OS X, a user with administrative privileges can start VNC Server in Service Mode. This means VNC Server runs, and users can connect, irrespective of whether or not a host computer user is currently logged on. (Note that connections are terminated on log off, but a disconnected user can reconnect after a few seconds.) By default, connecting users must know the user name and password of a member of the admin group in order to connect. Once connected, they have the same privileges (that is, access rights) as the currently logged on host computer user. For more information on privileges, see Authenticating connections to VNC Server.

Depending on the terms of the license, a host computer user can also, or alternatively, log on and start VNC Server in User Mode. This means VNC Server runs, and users can connect, just while this host computer user is logged on. (Connections are terminated on log off, though not on switch out if Fast User Switching is enabled.) By default, connecting users must know the user name and password of the host computer user starting VNC Server in order to connect. Once connected, they have the same privileges (that is, access rights) as this host computer user. For more information on privileges, see Authenticating connections to VNC Server.

Under Mac OS X, providing Fast User Switching is turned on, more than one host computer user can log on at a time. Each currently logged on host computer user can start VNC Server in User Mode, and all instances, for all users, run concurrently. Note that all instances, in either mode, must listen on different ports; see Configuring network communications for more information.

VNC Server can run as many times as the host computer’s license permits. Each time a host computer user starts VNC Server (whether in Service Mode or in User Mode), the count of the remaining permitted desktops (that is, instances of VNC Server) is decremented. To see how many desktops are left, type /library/vnc/vnclicense -check in a Terminal window. For more information on the message that is displayed, see the UNIX and Linux section above.