Section: Virtual Network Computing (1)
Updated: 03 Mar 2005
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vncviewer - VNC viewer for X
is a viewer (client) for Virtual Network Computing. This manual page documents
version 4 for the X window system.
If you run the viewer with no arguments it will prompt you for a VNC server to
connect to. Alternatively, specify the VNC server as an argument, e.g.:
where 'snoopy' is the name of the machine, and '2' is the display number of the
VNC server on that machine. Either the machine name or display number can be
omitted. So for example ":1" means display number 1 on the same machine, and
"snoopy" means "snoopy:0" i.e. display 0 on machine "snoopy".
If the VNC server is successfully contacted, you will be prompted for a
password to authenticate you. If the password is correct, a window will appear
showing the desktop of the VNC server.
AUTOMATIC PROTOCOL SELECTION
The viewer tests the speed of the connection to the server and chooses the
encoding and pixel format (colour level) appropriately. This makes it much
easier to use than previous versions where the user had to specify arcane
command line arguments.
The viewer normally starts out assuming the link is slow, using a low colour
level and using the encoding with the best compression. If it turns out that
the link is fast enough it switches to full-colour mode and will use an
encoding which compresses less but is faster to generate, thus improving the
interactive feel. Automatic selection can be turned off by setting the
AutoSelect parameter to false, or from the options dialog.
The viewer has a popup menu containing entries which perform various actions.
It is usually brought up by pressing F8, but this can be configured with the
MenuKey parameter. Actions which the popup menu can perform include:
switching in and out of full-screen mode
quitting the viewer
generating key events, e.g. sending ctrl-alt-del
accessing the options dialog and various other dialogs
By default, key presses in the popup menu get sent to the VNC server and
dismiss the popup. So to get an F8 through to the VNC server simply press it
FULL SCREEN MODE
A full-screen mode is supported. This is particularly useful when connecting
to a remote screen which is the same size as your local one. If the remote
screen is bigger, you can scroll by bumping the mouse against the edge of the
Unfortunately this mode doesn't work completely with all window managers, since
it breaks the X window management conventions.
You can get a list of parameters by giving -h as a command-line option
to vncviewer. Parameters can be turned on with -param or off with
-param=0. Parameters which take a value can be specified as
-param value. Other valid forms are param=value
-param=value --param=value. Parameter names are
Many of the parameters can also be set graphically via the options dialog box.
This can be accessed from the popup menu or from the "Connection details"
- -display Xdisplay
Specifies the X display on which the VNC viewer window should appear.
- -geometry geometry
Standard X position and sizing specification.
- -listen [port]
Causes vncviewer to listen on the given port (default 5500) for reverse
connections from a VNC server. WinVNC supports reverse connections initiated
using the 'Add New Client' menu option or the '-connect' command-line option.
Xvnc supports reverse connections with a helper program called
- -passwd password-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. It will usually be
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.
Specifies that no keyboard or mouse events should be sent to the server.
Useful if you want to view a desktop without interfering; often needs to be
Start in full-screen mode.
Use automatic selection of encoding and pixel format (default is on). Normally
the viewer tests the speed of the connection to the server and chooses the
encoding and pixel format appropriately. Turn it off with -AutoSelect=0.
- -FullColour, -FullColor
Tells the VNC server to send full-colour pixels in the best format for this
display. By default a low colour mode is used until AutoSelect decides the
link is fast enough. However if the server's native pixel format is
colourmapped (as opposed to truecolour) then the server's format is used by
- -LowColourLevel level
Selects the reduced colour level to use on slow links. level can range
from 0 to 2, 0 meaning 8 colours, 1 meaning 64 colours (the default), 2 meaning
- -PreferredEncoding encoding
This option specifies the preferred encoding to use from one of "ZRLE",
"hextile" or "raw".
Render the mouse cursor locally if the server supports it (default is on).
This can make the interactive performance feel much better over slow links.
- -WMDecorationWidth w, -WMDecorationHeight h
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 6, height 24.
- -log logname:dest:level
Configures the debug log settings. dest can currently be stderr or
stdout, and level is between 0 and 100, 100 meaning most verbose
output. logname is usually * meaning all, but you can target a
specific source file if you know the name of its "LogWriter". Default is
- -MenuKey keysym-name
This option specifies the key which brings up the popup menu. The key is
specified as an X11 keysym name (these can be obtained by removing the XK_
prefix from the entries in "/usr/include/X11/keysymdef.h"). Default is F8.
- -via gateway
Automatically create encrypted TCP tunnel to the gateway machine
before connection, connect to the host through that tunnel
(TightVNC-specific). By default, this option invokes SSH local port
forwarding, assuming that SSH client binary can be accessed as
/usr/bin/ssh. Note that when using the -via option, the host
machine name should be specified as known to the gateway machine, e.g.
"localhost" denotes the gateway, not the machine where vncviewer
was launched. The environment variable VNC_VIA_CMD can override
the default tunnel command of
/usr/bin/ssh -f -L "$L":"$H":"$R" "$G" sleep 20. The tunnel
command is executed with the environment variables L, H,
R, and G taken the values of the local port number, the remote
host, the port number on the remote host, and the gateway machine
Tristan Richardson, RealVNC Ltd.
VNC was originally developed by the RealVNC team while at Olivetti Research Ltd
/ AT&T Laboratories Cambridge. It is now being maintained by RealVNC Ltd. See
http://www.realvnc.com for details.
- AUTOMATIC PROTOCOL SELECTION
- POPUP MENU
- FULL SCREEN MODE
- OPTIONS (PARAMETERS)
- SEE ALSO
linux.jgfs.net manual pages