Understanding Virtual
Network Computing
VNC is a free, open source
remote control and
A
number of commercial products are currently available which allow remote
viewing/control of the desktop of a host machine. However, VNC differs
from these in a number of ways. Firstly, it is free; secondly, it is open source
(available for redistribution and modification under the GNU General Public Li
monitoring tool. It consists
cence); and thirdly, it is platform independent, so adding greatly to its versatility.
of viewer and server
VNC began its life at the Olivetti and Oracle Research Laboratory (ORL) as their
components, and its platform
Teleporting System this allowed the interface of an X Windows application to be
displayed on a remote machine. However, this had relatively heavy resource and
independence adds greatly to
bandwidth requirements, plus the X security model was an issue. In 1994 the
Videotile was built by ORL this was a display device with Pen, LCD screen and
its usefulness.
ATM connection. The VNC Protocol was developed from the Videotile, utilising the
method of only transmitting the parts of the screen that changed, so greatly reducing
By Phil Morris
bandwidth. In 1995 the Videotile mechanism was implemented in Java, so allowing
Technical Journalist
anyone with a Java equipped Web browser to access remote desktops running the
relevant server software. It was now possible to access remote desktops from
anywhere in the world, so providing far greater flexibility. The VNC Protocol was
then fully developed, so leading to the VNC viewers and servers described here. In
January 1999, AT&T acquired ORL, so making VNC a project of AT&T Labs,
Cambridge, UK.
Two Components
VNC consists of two main programs: the viewer and the server. The viewer is a small
program (150 KB in size for the Win32 version) which allows the remote PC to
connect to and view/control the desktop of the remote machine. No installation is
necessary for the viewer the relevant program for the operating system of choice
is simply run on the remote machine. The server does require an installation process
which differs according to the operating system the Win32 version, for example,
entails the use of a setup program, installation of the WinVNC Service, plus the
installation of the VNC hooks via a registry file. These two programs are explained
in greater detail below.
The VNC protocol is based on the concept of a Remote FrameBuffer (RFB), and
because it works at the framebuffer level it is versatile across a range of windowing
and operating systems and applications. It will operate over any reliable transport
protocol (such as TCP/IP). Because of the low bandwidth requirements it is a true
thin client protocol and will run on a wide range of hardware. The server by
necessity has more overheads than the viewer, but even this shouldn't stop it from
operating well on any PC available today.
VNC Servers
The main server program needs to be run on the host machine so viewers have
something to connect to. The server is currently available for X (Unix), Windows
and PPC Macintosh. There is also a version called rfbcounter, which is a simple
server produced with the aim of demonstrating that things other than desktops can
be displayed. Under Windows, the server can be run as an application or service,
but for various reasons it is recommended to run it as a service (for example, a user
doesn't then need to be logged into the server machine before a viewer can access
it). Once installed, the server can be set up to allow viewers to access it.
I will use the Windows version as an example. In this case, all the default settings
Issue 130:May 2001
PC Network Advisor
File: R1529.1
page 9
Review:Software
www.pcnetworkadvisor.com
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