xvncviewer1x

Usage

Overview

xvncviewer is a X viewer client for Xvnc, the free X server for Virtual Network Computing (VNC). It can connect to a running Xvnc server and display it in a X window. Further it can transmit mouse and keyevents to the server.

There are viewers for a variety of other plattforms, e.g. SVGAlib and Windows. For Linux and Windows also a server exists. With the built-in Java classes, you can even use a Java capable Internet browser to connect to Xvnc.

Examples

xvncviewer localhost:1

Connects to a running Xvnc session on the local workstation and displays its content in a X window.

xvncviewer -display :0 flora:1

Connects to a running Xvnc on host flora and displays its content in a X window of display :0 at localhost.

Options

-help

Prints a short usage notice to stderr.

-shared

When you make a connection to a VNC server, all other existing connections are normally closed. This option requests that they be left open, allowing you to share the desktop with someone already using it.

-viewonly

This option disables transfer of mouse and key events from the client to the server. This does not automatically imply -shared.

-fullscreen

Start in fullscreen mode.

-passwd file

If you are on a filesystem which gives you access to the password file used by the server, you can specify it here to avoid typing it in.

-encodings encoding-names

VNC provides several different compression encodings; this option specifies a set of them in order of preference. Encodings are specified separated with spaces, and must thus be enclosed in quotes if more than one is specified. Available encodings, in default order for a remote connection, are copyrect, hextile, corre, rre, and raw. For a local connection (to the same machine), the default order to try is raw, copyrect, hextile, corre, and rre.

-bgr233

Tells the VNC server to send pixels 8-bits deep. This reduces network traffic, but increases CPU utilization on servers deeper than 8 bits due to the translation required. Additionally, the colors are sometimes wrong. The bgr233 format is an 8-bit "true color" format, with 2 bits blue, 3 bits green, and 3 bits red. This is also the format used by the Java client.

-owncmap

This makes the viewer to install a private colormap on displays with a color depth of 8 bits.

-truecolour

Attempt to use a truecolour visual. (Americans should note the spelling of "colour".)

-depth

On an X-server which supports multiple true-color depths, attempt to use the specified one; if successful, this is the depth which will be requested from the VNC server. To force a particular depth from the vnc server, see the -bgr233 option.

-listen

This causes the viewer to listen on port 5500+displaynumber for reverse connections from a server. WinVNC supports reverse connections using the "Add New Client" menu option, or the -connect command line option.

Standard Xt Options - xvncviewer accepts the usual options; see X(3x) for more information. A few extremely common options are listed below.

-display num

This allows you to specify the X display on which the VNCviewer window should appear.

-geometry geometry-string

This specifies the initial size and location of the viewer window.

-compresslevel

Specifies the compression level to use (TightVNC).

-quality

Set the quality of the output (TightVNC).

-nocursorshape

Do not show the cursor from the workspace (TightVNC).

-noshared

Disallow sharing of the workspace.

-tunnel

Encodings

The server supplies information in whatever format is desired by the client, in order to make the client as easy as possible to implement. If the client represents itself as able to use multiple formats, the server will choose one.

Pixel format refers to the representation of an individual pixel. The most common formats are 24 and 16 bit "true-color" values, and 8-bit "color map" representations, where an arbitrary map converts the color number to RGB values.

Encoding refers to how a rectangle of pixels are sent (all information in VNC is sent as rectangles). All rectangles come with a header giving the location and size of the rectangle and an encoding type used by the data which follows. These types are listed below.

raw

The raw encoding simply sends width*height pixel values. All clients are required to support this encoding type. Raw is also the fastest when the server and viewer are on the same machine, as the connection speed is essentially infinite and raw encoding minimizes processing time.

copyrect

The Copy Rectangle encoding is efficient when something is being moved; the only data sent is the location of a rectangle from which data should be copied to the current location. Copyrect could also be used to efficiently transmit a repeated pattern.

RRE

The Rise-and-Run-length-Encoding is basically a 2D version of run-length encoding (RLE). In this encoding, a sequence of identical pixels are compressed to a single value and repeat count. In VNC, this is implemented with a background color, and then specifications of an arbitrary number of subrectangles and color for each. This is an efficient encoding for large blocks of constant color.

CoRRE

This is a minor variation on RRE, using a maximum of 255x255 pixel rectangles. This allows for single-byte values to be used, reducing packet size. This is in general more efficient, because the savings from sending 1-byte values generally outweighs the losses from the (relatively rare) cases where very large regions are painted the same color.

Hextile

Here, rectangles are split up in to 16x16 tiles, which are sent in a predetermined order. The data within the tiles is sent either raw or as a variant on RRE.

Other

Additional encodings, such as zlib, have been written, but are not a stock part of VNC. See http://www.uk.research.att.com/vnc/extras.html#zlib for more information.

Files

/usr/X11R6/bin/vncpasswd

Command to create and change password files to be used by the RFB protocol (can be specified with the -passwd option).

/usr/X11R6/bin/vncserver

A wrapper script around Xvnc to start the server with appropriate defaults.

/usr/X11R6/bin/Xvnc

The real server. Will be invoked by vncserver.