Xvnc - an X server providing VNC connectivity
- Xvnc
- [:display] [-geometry widthxheight]
[-depth depth] [-pixelformat rgb NNN|bgrNNN]
[-udpinputport port] [-rfbport port] [-rfbwait time]
[-nocursor] [-rfbauth passwd-file] [-httpd dir] [-httpport
port] [-deferupdate time] [-economictranslate] [-lazytight]
[-desktop name] [-alwaysshared] [-nevershared] [-dontdisconnect]
[-viewonly] [-localhost] [-interface ipaddr] [-inetd] [-compatiblekbd] [
X-options...]
Xvnc is a VNC (Virtual Network Computing) server. It acts like an X
server with a virtual display. The display can be seen by a VNC viewer
application, which may be running on a different machine: see
vncviewer(1). Xvnc is built inside the source code tree of XFree86, and
shares many options with it.
Normally, you don't need to start Xvnc manually; use the
vncserver(1)
wrapper script instead. This script sets reasonable defaults for Xvnc session,
checks many error conditions etc.
Please read the
BUGS section if you plan to use VNC on an untrusted
network.
Xvnc supports many standard X server options and a number of VNC-specific
options. To see what standard X server options are supported, please look at
the
Xvnc -help output and read the
Xserver(1) manual page
for details on those options.
The VNC-specific options are as follows:
-
-geometry widthxheight
- Set desktop width and height.
-
-depth depth
- Set the colour depth of the visual to provide, in bits per
pixel. Must be a value between 8 and 32.
-
-pixelformat
rgbNNN|bgrNNN
- Set colour format for pixels representation. The viewer can
do the conversion to any other pixel format, but it is faster if the depth
and pixel format of the server is the same as the equivalent values on the
viewer display.
-
-udpinputport port
- UDP port for keyboard/pointer data.
-
-rfbport port
- TCP port for RFB protocol. The RFB protocol is used for
communication between VNC server and clients.
-
-rfbwait time
- Maximum time, in milliseconds, to wait for an RFB client
(VNC viewer).
- -nocursor
- Don't put up a pointer cursor on the desktop.
-
-rfbauth passwd-file
- Use authentication on RFB protocol from the specified file.
The passwd-file can be created using the vncpasswd(1)
utility.
-
-httpd dir
- Serve files via HTTP protocol from the specified directory.
Normally, Java viewer classes are stored in such directory.
-
-httpport port
- TCP port on which Xvnc should listen for incoming HTTP
connections (to allow access to the desktop from any Java-capable
browser).
-
-deferupdate time
- Time in milliseconds, to defer screen updates (default 40).
Deferring updates helps to coalesce many small desktop changes into a few
larger updates thus saving network bandwidth.
- -economictranslate
- Use less memory-hungry pixel format translation.
- -lazytight
- Disable the "gradient" filter in Tight encoding
(TightVNC-specific). The "gradient" filter often helps to
improve data compression ratios, but may slow down the server performance.
Please note that this filter is never used when a client enables JPEG
compression in the Tight encoding.
-
-desktop name
- Set VNC desktop name ("x11" by default).
- -alwaysshared
- Always treat new clients as shared, never disconnect
existing client on a new client connection.
- -nevershared
- Never treat new clients as shared, do not allow several
simultaneous client connections.
- -dontdisconnect
- Don't disconnect existing clients when a new non-shared
connection comes in, refuse new connection instead.
- -viewonly
- Don't accept keboard and pointer events from clients. All
clients will be able to see the desktop but won't be able to control
it.
- -localhost
- Only allow loopback connections from localhost. This option
is useful in conjunction with SSH tunneling.
-
-interface ipaddr
- Listen for client connections only on the network interface
with given ipaddr.
- -inetd
- Xvnc is launched by inetd. This option causes Xvnc
to redirect network input/output to stdin/stdout.
- -compatiblekbd
- Set META and ALT keys to the same X modifier flag, as in
the original version of Xvnc by AT&T labs (TightVNC-specific).
There are many security problems in current Xvnc implementation. It's
recommended to restrict network access to Xvnc servers from untrusted network
addresses. Probably, the best way to secure Xvnc server is to allow only
loopback connections from the server machine (the
-localhost option)
and to use SSH tunneling for remote access to the Xvnc server. For details on
SSH tunneling, see
<URL:
http://www.cl.cam.ac.uk/Research/DTG/attarchive/vnc/sshvnc.html> .
vncserver(1),
vncviewer(1),
vncpasswd(1),
vncconnect(1),
sshd(1)
Original VNC was developed in AT&T Laboratories Cambridge. TightVNC
additions were implemented by Constantin Kaplinsky. Many other people
participated in development, testing and support.
Man page authors:
Marcus Brinkmann <
[email protected]>,
Tim Waugh <
[email protected]>,
Constantin Kaplinsky <
[email protected]>