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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 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  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  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
              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 automatically 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.