Xvnc(1) Virtual Network Computing Xvnc(1)NAMEXvnc - the X VNC server
SYNOPSISXvnc [options] :display#
DESCRIPTIONXvnc is the X VNC (Virtual Network Computing) server. It is based on a
standard X server, but it has a "virtual" screen rather than a physical
one. X applications display themselves on it as if it were a normal X
display, but they can only be accessed via a VNC viewer - see
vncviewer(1).
So Xvnc is really two servers in one. To the applications it is an X
server, and to the remote VNC users it is a VNC server. By convention
we have arranged that the VNC server display number will be the same as
the X server display number, which means you can use eg. snoopy:2 to
refer to display 2 on machine "snoopy" in both the X world and the VNC
world.
The best way of starting Xvnc is via the vncserver script. This sets
up the environment appropriately and runs some X applications to get
you going. See the manual page for vncserver(1) for more information.
OPTIONSXvnc takes lots of options - running Xvnc-help gives a list. Many of
these are standard X server options, which are described in the
Xserver(1) manual page.
-geometry widthxheight
Specify the size of the desktop to be created. Default is
640x480.
-depth depth
Specify the pixel depth in bits of the desktop to be created.
Default is 8, other possible values are 15, 16 and 24 - anything
else is likely to cause strange behaviour by applications.
-pixelformat format
Specify pixel format for server to use (BGRnnn or RGBnnn). The
default for depth 8 is BGR233 (meaning the most significant two
bits represent blue, the next three green, and the least signif‐
icant three represent red), the default for depth 16 is RGB565
and for depth 24 is RGB888.
-cc 3 As an alternative to the default TrueColor visual, this allows
you to run an Xvnc server with a PseudoColor visual (i.e. one
which uses a colour map or palette), which can be useful for
running some old X applications which only work on such a dis‐
play. Note that viewing such a desktop can be painful because
it usually results in a full-screen redraw every time an entry
in the colour map changes. Values other than 3 (PseudoColor)
and 4 (TrueColor) for the -cc option may result in strange be‐
haviour, and PseudoColor desktops must be 8 bits deep.
-rfbport port
Specifies the TCP port on which Xvnc listens for connections
from viewers (the protocol used in VNC is called RFB - "remote
framebuffer"). The default is 5900 plus the display number.
-rfbwait time
Time in milliseconds to wait for a viewer which is blocking
Xvnc. This is necessary because Xvnc is single-threaded and
sometimes blocks until the viewer has finished sending or
receiving a message - note that this does not mean an update
will be aborted after this time. Default is 20000 (20 seconds).
-nocursor
Don't draw a cursor. This can be useful when debugging a viewer
to make the updates drawn more predictable.
-rfbauth passwd-file
Specifies the file containing the password used to authenticate
viewers. The file is accessed each time a connection comes in,
so it can be changed on the fly via vncpasswd(1).
-httpd directory
Run a mini-HTTP server which serves files from the given direc‐
tory. Normally the directory will contain the classes for the
Java viewer. In addition, files with a .vnc extension will have
certain substitutions made so that a single installation of the
Java VNC viewer can be served by separate instances of Xvnc.
-httpport port
Specifies the port on which the mini-HTTP server runs. Default
is 5800 plus the display number.
-deferupdate time
Xvnc uses a "deferred update" mechanism which enhances perfor‐
mance in many cases. After any change to the framebuffer, Xvnc
waits for this number of milliseconds (default 40) before send‐
ing an update to any waiting clients. This means that more
changes tend to get coalesced together in a single update. Set‐
ting it to 0 results in the same behaviour as earlier versions
of Xvnc, where the first change to the framebuffer causes an
immediate update to any waiting clients.
-economictranslate
The server normally uses a lookup table for translating pixel
values when the viewer requests a different format from the
native one used by the server. This can use up to 256Kbytes per
connected viewer, so if you have many viewers you may wish to
specify this option which will save memory at the expense of a
little bit of speed. Only relevant for 16-bit-deep desktops.
-maxrects num
Sets the maximum number of rectangles Xvnc will send in one
update. If an update would consist of more than this many rec‐
tangles, then an update of a single bounding rectangle is sent
instead. This makes sense because sending a large number of
small rectangles is less efficient than sending one large rec‐
tangle, even when this means updating pixels which haven't actu‐
ally changed. The default is 50.
-desktop desktop-name
Each desktop has a name which may be displayed by the viewer. It
defaults to "x11".
-alwaysshared
Always treat new clients as shared (i.e. ignore client's shared
flag).
-nevershared
Never treat new clients as shared (i.e. ignore client's shared
flag).
-dontdisconnect
Don't disconnect existing clients when a new "non-shared" con‐
nection comes in. Instead the new connection is refused. New
"shared" connections are still allowed in the normal way.
-localhost
Only allow connections from the same machine. Useful if you use
SSH and want to stop non-SSH connections from any other hosts.
See the guide to using VNC with SSH on the web site.
-inetd This significantly changes Xvnc's behaviour so that it can be
launched from inetd. Instead of listening for TCP connections it
uses its standard input and standard output as a connection to
the VNC viewer. See the information on the extras page on the
web site for details.
SEE ALSOvncconnect(1), vncpasswd(1), vncserver(1), vncviewer(1), Xserver(1)
http://www.realvnc.com
AUTHOR
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.
RealVNC Ltd 28 February 2003 Xvnc(1)