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Xvnc(1)			   Virtual Network Computing		       Xvnc(1)

       Xvnc - the X VNC	server

       Xvnc [options] :display#

       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	 accessed  via	a  VNC	viewer	-  see

       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

       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.

       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

       -depth depth
	      Specify  the  pixel  depth in bits of the	desktop	to be created.
	      Default is 16, other possible values are 8, 15, and  24  -  any-
	      thing 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.   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

       VNC parameters can be set both via the  command-line  and  through  the
       vncconfig(1) program, and with a	VNC-enabled XFree86 server via Options
       entries in the XF86Config file.

       Parameters can be turned	on with	-param or off with -param=0.   Parame-
       ters  which take	a value	can be specified as -param value.  Other valid
       forms are param=value -param=value --param=value.  Parameter names  are

       -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 protocol 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	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).

       -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.

       -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 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 im-
	      mediate update to	any waiting clients.

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

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

	      Accept pointer press and release events from clients (default is

	      Accept key press and release events  from	 clients  (default  is

	      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.

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

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

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

	      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 re-
	      quire 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 3600 i.e. an hour).

	      Prompts  the  user of the	desktop	to explicitly accept or	reject
	      incoming connections.  This is most useful when using the
	      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 module or
	      Xvnc(1) program.	The x0vncserver(1) program  does  not  require
	      vncconfig(1) to be running.

	      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 ver-
	      bose output.  logname is usually * meaning all, but you can tar-
	      get a specific source file if you	know the  name	of  its	 "Log-
	      Writer".	Default	is *:stderr:30.

       -RemapKeys mapping
	      Sets up a	keyboard mapping.  mapping is a	comma-separated	string
	      of  character  mappings,	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 following:


       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 associated 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  usu-
       ally 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.  Further 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  as-
       sociated	 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  session 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 created automatically the
       next time he connects.

       vncconfig(1), vncpasswd(1), vncserver(1), vncviewer(1), Xserver(1), in-

       Tristan Richardson, RealVNC Ltd.

       VNC  was	originally developed by	the RealVNC team while at Olivetti Re-
       search Ltd / AT&T Laboratories Cambridge.  It is	now  being  maintained
       by RealVNC Ltd.	See for details.

RealVNC	Ltd			  03 Mar 2005			       Xvnc(1)


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