MAN page from Mandriva 2006 tightvnc-1.2.9-6mdk.i586.rpm


Section: TightVNC (1)
Updated: January 2003


vncviewer - an X viewer client for VNC 




vncvieweris an Xt-based client application for the VNC (Virtual NetworkComputing) system. It can connect to any VNC-compatible server suchas Xvnc or WinVNC, allowing you to control desktop environmentof a different machine.

You can use F8 to display a pop-up utility menu. Press F8 twice topass single F8 to the remote side. 


Prints a short usage notice to stderr.
Make the viewer listen on port 5500+display for reverseconnections from a server. WinVNC supports reverse connections usingthe "Add New Client" menu option, or the -connect command lineoption. Xvnc requires the use of the helper programvncconnect.
-via gateway
Automatically create encrypted TCP tunnel to the gateway machinebefore connection, connect to the host through that tunnel(TightVNC-specific). By default, this option invokes SSH local portforwarding, assuming that SSH client binary can be accessed as/usr/bin/ssh. Note that when using the -via option, the hostmachine name should be specified as known to the gateway machine, e.g. "localhost" denotes the gateway, not the machine where vncviewerwas launched. See the ENVIRONMENT section below for the information onconfiguring the -via option.
When connecting, specify that a shared connection is requested. InTightVNC, this is the default mode, allowing you to share the desktopwith other clients already using it.
When connecting, specify that the session may not be shared. Thiswould either disconnect other connected clients or refuse yourconnection, depending on the server configuration.
Disable transfer of mouse and keyboard events from the client to theserver.
Start in full-screen mode. Please be aware that operating infull-screen mode may confuse X window managers. Typically, suchconflicts cause incorrect handling of input focus or make the viewerwindow disappear mysteriously. See the grabKeyboard setting in theRESOURCES section below for a method to solve input focus problem.
By default, the viewer shows and raises its window on remote beep(bell) event. This option disables such behaviour(TightVNC-specific).
-passwd passwd-file
File from which to get the password (as generated by thevncpasswd(1) program).
-encodings encoding-list
TightVNC supports several different compression methods to encodescreen updates; this option specifies a set of them to use in order ofpreference. Encodings are specified separated with spaces, and mustthus be enclosed in quotes if more than one is specified. Availableencodings, in default order for a remote connection, are "copyrecttight hextile zlib corre rre raw". For a local connection (to the samemachine), the default order to try is "raw copyrect tight hextile zlibcorre rre". Raw encoding is always assumed as a last option if noother encoding can be used for some reason. For more information onencodings, see the section ENCODINGS below.
Always use the BGR233 format to encode pixel data. This reducesnetwork traffic, but colors may be represented inaccurately. Thebgr233 format is an 8-bit "true color" format, with 2 bits blue, 3bits green, and 3 bits red.
Try to use a PseudoColor visual and a private colormap. This allowsthe VNC server to control the colormap.
-truecolour, -truecolor
Try to use a TrueColor visual.
-depth depth
On an X server which supports multiple TrueColor visuals of differentdepths, attempt to use the specified one (in bits per pixel); ifsuccessful, this depth will be requested from the VNC server.
-compresslevel level
Use specified compression level (0..9) for "tight" and "zlib"encodings (TightVNC-specific). Level 1 uses minimum of CPU time andachieves weak compression ratios, while level 9 offers bestcompression but is slow in terms of CPU time consumption on the serverside. Use high levels with very slow network connections, and lowlevels when working over high-speed LANs. It's not recommended to usecompression level 0, reasonable choices start from the level 1.
-quality level
Use the specified JPEG quality level (0..9) for the "tight"encoding (TightVNC-specific). Quality level 0 denotes bad imagequality but very impressive compression ratios, while level 9 offersvery good image quality at lower compression ratios. Note that the"tight" encoder uses JPEG to encode only those screen areas that looksuitable for lossy compression, so quality level 0 does not alwaysmean unacceptable image quality.
Disable lossy JPEG compression in Tight encoding (TightVNC-specific). Disabling JPEG compression is not a good idea in typical cases, asthat makes the Tight encoder less efficient. You might want to usethis option if it's absolutely necessary to achieve perfect imagequality (see also the -quality option).
Disable cursor shape updates, protocol extensions used to handleremote cursor movements locally on the client side(TightVNC-specific). Using cursor shape updates decreases delays withremote cursor movements, and can improve bandwidth usage dramatically.
Use a real X11 cursor with X-style cursor shape updates, instead ofdrawing the remote cursor on the framebuffer. This option alsodisables the dot cursor, and disables cursor position updates innon-fullscreen mode.


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

Pixel formatrefers to the representation of an individual pixel. The most commonformats are 24 and 16 bit "true-color" values, and 8-bit "color map"representations, where an arbitrary map converts the color number toRGB values.

Encodingrefers to how a rectangle of pixels are sent (all pixel information inVNC is sent as rectangles). All rectangles come with a header givingthe location and size of the rectangle and an encoding type used bythe data which follows. These types are listed below.

The raw encoding simply sends width*height pixel values. All clientsare required to support this encoding type. Raw is also the fastestwhen the server and viewer are on the same machine, as the connectionspeed is essentially infinite and raw encoding minimizes processingtime.
The Copy Rectangle encoding is efficient when something is beingmoved; the only data sent is the location of a rectangle from whichdata should be copied to the current location. Copyrect could also beused to efficiently transmit a repeated pattern.
The Rise-and-Run-length-Encoding is basically a 2D version ofrun-length encoding (RLE). In this encoding, a sequence of identicalpixels are compressed to a single value and repeat count. In VNC, thisis implemented with a background color, and then specifications of anarbitrary number of subrectangles and color for each. This is anefficient encoding for large blocks of constant color.
This is a minor variation on RRE, using a maximum of 255x255 pixelrectangles. This allows for single-byte values to be used, reducingpacket size. This is in general more efficient, because the savingsfrom sending 1-byte values generally outweighs the losses from the(relatively rare) cases where very large regions are painted the samecolor.
Here, rectangles are split up in to 16x16 tiles, which are sent in apredetermined order. The data within the tiles is sent either raw oras a variant on RRE. Hextile encoding is usually the best choice forusing in high-speed network environments (e.g. Ethernet local-areanetworks).
Zlib is a very simple encoding that uses zlib library to compress rawpixel data. This encoding achieves good compression, but consumes alot of CPU time. Support for this encoding is provided forcompatibility with VNC servers that might not understand Tightencoding which is more efficient than Zlib in nearly all real-lifesituations.
Like Zlib encoding, Tight encoding uses zlib library to compress thepixel data, but it pre-processes data to maximize compression ratios,and to minimize CPU usage on compression. Also, JPEG compression maybe used to encode color-rich screen areas (see the description of-quality and -nojpeg options above). Tight encoding is usually thebest choice for low-bandwidth network environments (e.g. slow modemconnections).


X resources that vncviewer knows about, aside from thenormal Xt resources, are as follows:
Equivalent of -shared/-noshared options. Default true.
Equivalent of -viewonly option. Default false.
Equivalent of -fullscreen option. Default false.
Grab keyboard in full-screen mode. This can help to solve problemswith losing keyboard focus. Default false.
Equivalent of -noraiseonbeep option, when set to false. Defaulttrue.
Equivalent of -passwd option.
Whether to use a dialog box to get the password (true) or get it fromthe tty (false). Irrelevant if passwordFile is set. Defaultfalse.
Equivalent of -encodings option.
Equivalent of -compresslevel option (TightVNC-specific).
Equivalent of -quality option (TightVNC-specific).
Equivalent of -nojpeg option, when set to false. Default true.
Equivalent of -nocursorshape option, when set to false(TightVNC-specific). Default true.
Equivalent of -bgr233 option. Default false.
When using BGR233, try to allocate this many "exact" colors from theBGR233 color cube. When using a shared colormap, setting this resourcelower leaves more colors for other X clients. Irrelevant when usingtruecolor. Default is 256 (i.e. all of them).
If the number of "exact" BGR233 colors successfully allocated is lessthan 256 then the rest are filled in using the "nearest" colorsavailable. This resource says whether to only use the "exact" BGR233colors for this purpose, or whether to use other clients' "shared"colors as well. Default true (i.e. use other clients' colors).
Equivalent of -owncmap option. Default false.
Equivalent of -truecolour option. Default false.
Equivalent of -depth option.
Use MIT shared memory extension if on the same machine as the Xserver. Default true.
wmDecorationWidth, wmDecorationHeight
The total width and height taken up by window manager decorations.This is used to calculate the maximum size of the VNC viewer window. Default is width 4, height 24.
bumpScrollTime, bumpScrollPixels
When in full screen mode and the VNC desktop is bigger than the Xdisplay, scrolling happens whenever the mouse hits the edge of thescreen. The maximum speed of scrolling is bumpScrollPixels pixelsevery bumpScrollTime milliseconds. The actual speed of scrolling willbe slower than this, of course, depending on how fast your machine is. Default 20 pixels every 25 milliseconds.
The number of buttons in the popup window. See the README file formore information on how to customize the buttons.
For debugging. Default false.
rawDelay, copyRectDelay
For debugging, see the README file for details. Default 0 (off).


When started with the -via option, vncviewer reads theVNC_VIA_CMD environment variable, expands patterns beginningwith the "%" character, and executes result as a command assuming thatit would create TCP tunnel that should be used for VNC connection. Ifnot set, this environment variable defaults to "/usr/bin/ssh -f -L%L:%H:%R %G sleep 20".

The following patterns are recognized in the VNC_VIA_CMD (notethat all the patterns %G, %H, %L and %R must be present in the commandtemplate):

A literal "%";
gateway host name;
remote VNC host name, as known to the gateway;
local TCP port number;
remote TCP port number.


vncserver(1), Xvnc(1), vncpasswd(1),vncconnect(1), ssh(1) 


Original VNC was developed in AT&T Laboratories Cambridge. TightVNCadditions was implemented by Constantin Kaplinsky. Many other peopleparticipated in development, testing and support.

Man page authors:
Marcus Brinkmann <>,
Terran Melconian <>,
Tim Waugh <>,
Constantin Kaplinsky <>




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