xvnc(1)

NAME

Xvnc - the X VNC server

SYNOPSIS

Xvnc [options] :display#

DESCRIPTION

Xvnc 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 ac

cessed 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 serv

er. 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 appli

cations to get you going. See the manual page for vncserver(1)

for more information.

OPTIONS

Xvnc takes lots of options - running Xvnc -help gives a

list. Many of these are standard X server options, which are de

scribed in the Xserver(1) manual page.

-geometry widthxheight

Specify the size of the desktop to be created. De

fault 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 applica

tions.

-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 significant 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 use

ful for running some old X applications which only work on such a

display. 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 behaviour,

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 re

ceiving 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 de

bugging 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 connec

tion 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 directory. 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 installa

tion 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 en

hances performance in many cases. After any change to the frame

buffer, Xvnc waits for this number of milliseconds (default 40)

before sending an update to any waiting clients. This means that

more changes tend to get coalesced together in a single update.

Setting it to 0 results in the same behaviour as earlier versions

of Xvnc, where the first change to the framebuffer causes an im

mediate update to any waiting clients.

-economictranslate

The server normally uses a lookup table for trans

lating 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 ex

pense 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 rectangles, 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 rectan

gle, even when this means updating pixels which haven't actually

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" connection comes in. Instead the new connection is re

fused. New "shared" connections are still allowed in the normal

way.

-localhost

Only allow connections from the same machine. Use

ful 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 con

nections it uses its standard input and standard output as a con

nection to the VNC viewer. See the information on the extras page

on the web site for details.

SEE ALSO

vncconnect(1), vncpasswd(1), vncserver(1), vncviewer(1),

Xserver

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)