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A few weeks ago we reviewed the Sharp Zaurus handheld, a fine piece of engineering that Sharp finally remembered we had and wanted back. Darn.

Anyway, in that column we mentioned a piece of remote control software called Virtual Network Computing (VNC) created by the unlikely combination of AT&T Laboratories and the University of Cambridge.

VNC is a remote control system that lets you see the monitor display of a remote computer and makes your keyboard and mouse act as the remote computer's keyboard and mouse.

The authors note that VNC is different from other remote control solutions in that: "It is fully cross-platform [note that there is no Mac support yet - Gearhead]. A desktop running on a Linux machine might be displayed on a Windows PC, on a Solaris machine, or on any number of other architectures. There is a Java viewer so that any desktop can be viewed with any Java-capable browser. There is a Windows server, allowing you to view the desktop of a remote Windows machine on any of these platforms using exactly the same viewer. The simplicity of the protocol makes it easy to port to new platforms, and other people have therefore ported VNC to a huge variety of platforms."

They also say it "is small and simple. The Windows viewer, for example, is about 150K in size and can be run directly from a floppy. The entire Java viewer is substantially less than 100K and takes less time to download than the images on some Web pages."

Finally, the company announces that VNC "is free! You can download it (www.realvnc.com/download.html), use it, and redistribute it under the terms of the GNU General Public License." You also can get the full source code, and there's in-depth how-it-works information at www.realvnc.com/howitworks.html, including a discussion of the underlying protocol.

VNC is a remarkable package. It literally takes minutes to install, it is robust and it is fast. The machine to be monitored is the server and the remote viewer is the client. But there are some important considerations if you're going to use it. First, it's not really secure (although compared with telnet access, VNC is more like Fort Knox).

To route VNC connections through a firewall you'll have to set up your firewall to allow connections to the VNC ports. VNC can support many servers on a machine so a VNC server will accept connections on port 5900+N, where N is the server's number.


Virtual Network Computing

Functionality A
Value for money A

Overall grade

Vendor:AT&T and the University of Cambridge

The built-in Web server that services the Java VNC Viewer is accessible via port 5800+N but VNC traffic is not encrypted so this is a potential security problem.

The only built-in security in VNC is basic password encryption, so if you're paranoid you'll want to use VNC with Secure Shell  (SSH).

VNC came to our attention again with a new release on Sept. 25 - Version 3.3.4. The two most significant improvements are:

• First, VNC "automatically optimizes the choice of encoding and pixel format based on an estimate of line speed. In most cases now the viewer will adapt to slow and fast links without needing extra command-line options. This is particularly useful if the desktop is viewed in the office over a good LAN connection, then later at home over a slow link. On connection, the algorithm assumes a slow link and uses eight-bit color and ZRLE [see the next item]. If the network seems fast, we switch to full-color. If the network seems really fast, we also switch to hextile rather than ZRLE. If server and viewer are on the same machine, we use raw."

• Second, the VNC team says ZRLE is "another significant development." This is apparently a new encoding method that works well with slow links and is "a combination of the run-length encoding scheme with tiling, palettization and ZLIB compression."

There also are all sorts of new management and configuration features, and the documentation is more thorough. We've been running the 3.3.4 release for a few hours and it not only looks stable, the Java client works great and the whole system is faster. Let us know your experiences with VNC. A great piece of software!

Tell us if you're experienced at gearhead@gibbs.com.

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