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 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.

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 16, other possible values are 8, 15, 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 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 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 XFree86 server via Options
       entries in the XF86Config 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 protocol used in VNC is called RFB -  "remote  frame-
	      buffer").  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 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 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 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 setting (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 3600 i.e. an hour).

       -QueryConnect
	      Prompts the user of the desktop to explicitly accept or reject incoming connections.  This is most useful when using the vnc.so mod-
	      ule 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 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:

		 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 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 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.  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 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 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  automati-
       cally the next time he connects.

SEE ALSO

       vncconfig(1), vncpasswd(1), vncserver(1), vncviewer(1), Xserver(1), inetd(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							    03 Mar 2005 							   Xvnc(1)