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Xvnc(1) 			    Virtual Network Computing				  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  them-
       selves  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 vnc-
       server(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	described  in the Xserver(1) manual page.  In addition to
       options which can only be set via the command-line, there are also "parameters" which  can
       be set both via the command-line and through the vncconfig(1) program.

       -geometry widthxheight
	      Specify the size of the desktop to be created. Default is 1024x768.

       -depth depth
	      Specify  the pixel depth in bits of the desktop to be created. Default is 24, other
	      possible values are 8, 15, and 16 - anything else is likely to cause strange behav-
	      iour 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 significant three represent red), the default for depth 16 is
	      RGB565 and for depth 24 is RGB888.

       -interface IP address or -i IP address
	      Listen on interface. By default Xvnc listens on all available interfaces.

       -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 color map or palette),
	      which can be useful for running some old X applications which only work on  such	a
	      display.	 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 (i.e.
	      -depth 8).

       -inetd This  significantly changes Xvnc's behaviour so that it can be launched from inetd.
	      See the section below on usage with inetd.

       -help  List all the options and parameters

PARAMETERS
       VNC parameters can be set both via the command-line and through the vncconfig(1)  program,
       and with a VNC-enabled Xorg server via Options entries in the xorg.conf file.

       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 case-insensitive.

       -desktop desktop-name
	      Each desktop has a name which may be displayed by the viewer. It defaults to "x11".

       -rfbport port
	      Specifies the TCP port on which Xvnc listens for connections from viewers (the pro-
	      tocol used in VNC is called RFB - "remote framebuffer").	The default is 5900  plus
	      the display number.

       -rfbwait time, -ClientWaitTimeMillis time

	      Time  in	milliseconds to wait for a viewer which is blocking Xvnc.  This is neces-
	      sary because Xvnc is single-threaded and sometimes blocks until the viewer has fin-
	      ished  sending or receiving a message - note that this does not mean an update will
	      be aborted after this time.  Default is 20000 (20 seconds).

       -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  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.

       -rfbauth passwd-file, -PasswordFile 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).

       -deferUpdate time
	      Xvnc uses a "deferred update" mechanism which enhances performance in  many  cases.
	      After  any  change  to  the framebuffer, Xvnc waits for this number of milliseconds
	      (default 1) 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 immediate update to any waiting clients.

       -SendCutText
	      Send  clipboard  changes	to  clients (default is on).  Note that you must also run
	      vncconfig(1) to get the clipboard to work.

       -AcceptCutText
	      Accept clipboard updates from clients (default is on).  Note that you must also run
	      vncconfig(1) to get the clipboard to work.

       -AcceptPointerEvents
	      Accept pointer press and release events from clients (default is on).

       -AcceptKeyEvents
	      Accept key press and release events from clients (default is on).

       -DisconnectClients
	      Disconnect  existing  clients  if  an incoming connection is non-shared (default is
	      on). If DisconnectClients is false,  then  a  new  non-shared  connection  will  be
	      refused  while there is a client active.	When combined with NeverShared this means
	      only one client is allowed at a time.

       -NeverShared
	      Never treat incoming connections as shared, regardless of the client-specified set-
	      ting (default is off).

       -AlwaysShared
	      Always  treat  incoming  connections  as shared, regardless of the client-specified
	      setting (default is off).

       -Protocol3.3
	      Always use protocol version 3.3  for  backwards  compatibility  with  badly-behaved
	      clients (default is off).

       -CompareFB
	      Perform  pixel  comparison on framebuffer to reduce unnecessary updates (default is
	      on).

       -SecurityTypes sec-types
	      Specify which security schemes to use separated by commas.  At present only  "None"
	      and  "VncAuth"  are  supported.  The default is "VncAuth" - note that if you want a
	      server which does not require a password, you must set this parameter to "None".

       -IdleTimeout seconds
	      The number of seconds after which an idle VNC connection will be	dropped  (default
	      is 0, which means that idle connections will never be dropped).

       -QueryConnect
	      Prompts  the  user  of  the desktop to explicitly accept or reject incoming connec-
	      tions.  This is most useful when using the vnc.so module or x0vncserver(1)  program
	      to access an existing X desktop via VNC.

	      The  vncconfig(1)  program must be running on the desktop in order for QueryConnect
	      to be supported by the vnc.so(1) module or  Xvnc(1)  program.   The  x0vncserver(1)
	      program does not require vncconfig(1) to be running.

       -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.

       -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 *:stderr:30.

       -RemapKeys mapping
	      Sets up a keyboard mapping.  mapping is a comma-separated string of character  map-
	      pings,  each  of	the  form  char->char, or char<>char, where char is a hexadecimal
	      keysym. For example, to exchange the " and @ symbols you would specify the  follow-
	      ing:

		 RemapKeys=0x22<>0x40

USAGE WITH INETD
       By  configuring	the inetd(1) service appropriately, Xvnc can be launched on demand when a
       connection comes in, rather than having to be started manually.	 When  given  the  -inetd
       option,	instead  of  listening	for  TCP connections on a given port it uses its standard
       input and standard output.  There are two modes controlled by the wait/nowait entry in the
       inetd.conf file.

       In  the nowait mode, Xvnc uses its standard input and output directly as the connection to
       a viewer.  It never has a listening socket, so  cannot  accept  further	connections  from
       viewers (it can however connect out to listening viewers by use of the vncconfig program).
       Further viewer connections to the same TCP port result in inetd spawning off a new Xvnc to
       deal with each connection.  When the connection to the viewer dies, the Xvnc and any asso-
       ciated X clients die.  This behaviour is most useful when combined with the XDMCP  options
       -query and -once.  An typical example in inetd.conf might be (all on one line):

       5950    stream	tcp nowait nobody  /usr/local/bin/Xvnc Xvnc -inetd -query localhost -once
       securitytypes=none

       In this example a viewer connection to :50 will result in a new Xvnc for  that  connection
       which  should  display  the  standard  XDM login screen on that machine.  Because the user
       needs to login via XDM, it is usually OK to accept connections without a VNC  password  in
       this case.

       In  the wait mode, when the first connection comes in, inetd gives the listening socket to
       Xvnc.  This means that for a given TCP port, there is only ever one Xvnc at a time.   Fur-
       ther  viewer connections to the same port are accepted by the same Xvnc in the normal way.
       Even when the original connection is broken, the Xvnc will continue to run.   If  this  is
       used  with  the XDMCP options -query and -once, the Xvnc and associated X clients will die
       when the user logs out of the X session in the normal way.  It is important to use  a  VNC
       password in this case.  A typical entry in inetd.conf might be:

       5951    stream	 tcp  wait    james	 /usr/local/bin/Xvnc Xvnc -inetd -query localhost
       -once passwordFile=/home/james/.vnc/passwd

       In fact typically, you would have one entry for each user who uses VNC regularly, each  of
       whom  has their own dedicated TCP port which they use.  In this example, when user "james"
       connects to :51, he enters his VNC password, then gets the XDM login screen where he  logs
       in  in  the normal way.	However, unlike the previous example, if he disconnects, the ses-
       sion remains persistent, and when he reconnects he will get the same session  back  again.
       When he logs out of the X session, the Xvnc will die, but of course a new one will be cre-
       ated automatically the next time he connects.

SEE ALSO
       vncconfig(1), vncpasswd(1), vncserver(1), vncviewer(1), Xserver(1), inetd(1)
       http://www.tigervnc.org

AUTHOR
       Tristan Richardson, RealVNC Ltd.

       VNC was originally developed by the RealVNC team while at Olivetti  Research  Ltd  /  AT&T
       Laboratories Cambridge.	TightVNC additions were implemented by Constantin Kaplinsky. Many
       other people participated in development, testing and support.

TigerVNC				   17 Apr 2006					  Xvnc(1)
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