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Virtual Network Computing (VNC) is a desktop sharing system which uses the RFB (Remote FrameBuffer) protocol to remotely control another computer. It transmits the keyboard presses and mouse clicks from one computer to another relaying the screen updates back in the other direction, over a network.

VNC is platform-independent: a VNC viewer on any operating system can connect to a VNC server on any other operating system. There are clients and servers for almost all operating systems and for Java. Multiple clients may connect to a VNC server at the same time. Popular uses of the technology include remote technical support, and accessing files on one's work computer from one's home computer.

VNC has two parts, a client and a server. The server is the program on the machine that shares its screen, and the client (or viewer) is the program that watches and interacts with the server.

VNC is a very simple protocol, based on one graphic primitive: "Put a rectangle of pixel data at a given x, y position". That is, the server sends small rectangles of the framebuffer to the client. This in its simplest form uses a lot of bandwidth, so various methods are used to reduce it. For example, there are various encodings - methods to determine the most efficient way to transfer these rectangles. The VNC protocol allows the client and server to negotiate which encoding will be used. The simplest encoding, which is supported by all clients and servers, is the raw encoding where pixel data is sent in left-to-right scanline order, and after initial setup, then only transfers rectangles that change. Because of that, this encoding works very well if only a small portion of the screen changes from one frame to the next (like a mouse pointer moving across a desktop, or text being written at the cursor), but bandwidth demands get very high if a lot of pixels change. (Full screen video is the most radical example of this.)

VNC by default uses ports 5900 to 5906, each representing the corresponding X screen (ports 5900 to 5906, for screens :0 to :6). A Java viewer is available in many implementations such as RealVNC on ports 5800 to 5806, following the same pattern. These ports can be changed.

ChromiVNC Server for System 7

ChromiVNC is extremely stable running under Mac OS 7.6.1 on a PowerPC Mac. In fact, with multiple connections and disconnections to this server from client machines, I have yet to have it crash. However, I have not tested it on other systems. The server software is 68k and PowerPC compatible, however the included vncPatches extension is PowerPC only. If anybody knows where I can find the 68k version, or have tested this on previous system versions, please let me know.

Minimum System Requirements

Spec Details
Operating System: Mac OS 7.6.1
Processor: 60mhz PowerPC
RAM: 12 MB


ChromiVNC Server 3.4a5

VNC Viewer for System 7

VNC Viewer is a nice, small VNC Viewer by Tim Senecal that works on Mac OS 7.6.1 PowerPC test systems. Giving it more RAM helps it display larger resolution servers better. I assigned 10mb of RAM to VNC Viewer, and had no trouble displaying a 1440 x 900 iMac G5 screen on my PowerBook Duo. The VNC Viewer program even allows you to scale larger resolutions down to the size of your window, or your screen (should you be in full screen mode). There are both 68k and PowerPC versions of this program.

Minimum System Requirements

Spec Details
Operating System: Mac OS 7.6
Processor: 68k or PowerPC
RAM: 12 MB


VNC Viewer PowerPC

VNC Viewer 68k

Servers & Clients for Other Platforms

Mac OS X: Server (Share My Desktop) | Client (Chicken of the VNC)

Windows: Server (UltraVNC Server) | Client (UltraVNC Viewer)

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