xvnc(1): X server providing VNC connectivity

NAME

Xvnc - an X server providing VNC connectivity

SYNOPSIS

Xvnc: [:display] [-geometry widthxheight] [-depth depth] [-pixelformat rgbNNN|bgrNNN] [-udpinputport port] [-rfbport port] [-rfbwait time] [-nocursor] [-rfbauth passwd-file] [-httpd dir] [-httpport port] [-deferupdate time] [-economictranslate] [-lazytight] [-desktop name] [-alwaysshared] [-nevershared] [-dontdisconnect] [-viewonly] [-localhost] [-interface ipaddr] [-inetd] [-compatiblekbd] [X-options...]

DESCRIPTION

Xvnc is a VNC (Virtual Network Computing) server. It acts like an X server with a virtual display. The display can be seen by a VNC viewer application, which may be running on a different machine: see vncviewer(1). Xvnc is built inside the source code tree of XFree86, and shares many options with it.

Normally, you don't need to start Xvnc manually; use the vncserver(1) wrapper script instead. This script sets reasonable defaults for Xvnc session, checks many error conditions etc.

Please read the BUGS section if you plan to use VNC on an untrusted network.

OPTIONS

Xvnc supports many standard X server options and a number of VNC-specific options. To see what standard X server options are supported, please look at the Xvnc -help output and read the xserver(1) manual page for details on those options.

The VNC-specific options are as follows:

-geometry widthxheight: Set desktop width and height.
-depth depth: Set the colour depth of the visual to provide, in bits per pixel. Must be a value between 8 and 32.
-pixelformat rgbNNN|bgrNNN: Set colour format for pixels representation. The viewer can do the conversion to any other pixel format, but it is faster if the depth and pixel format of the server is the same as the equivalent values on the viewer display.
-udpinputport port: UDP port for keyboard/pointer data.
-rfbport port: TCP port for RFB protocol. The RFB protocol is used for commnunication between VNC server and clients.
-rfbwait time: Maximum time, in milliseconds, to wait for an RFB client (VNC viewer).
-nocursor: Don't put up a pointer cursor on the desktop.
-rfbauth passwd-file: Use authentication on RFB protocol from the specified file. The passwd-file can be created using the vncpasswd(1) utility.
-httpd dir: Serve files via HTTP protocol from the specified directory. Normally, Java viewer classes are stored in such directory.
-httpport port: TCP port on which Xvnc should listen for incoming HTTP connections (to allow access to the desktop from any Java-capable browser).
-deferupdate time: Time in milliseconds, to defer screen updates (default 40). Deferring updates helps to coalesce many small desktop changes into a few larger updates thus saving network bandwidth.
-economictranslate: Use less memory-hungry pixel format translation.
-lazytight: Disable the "gradient" filter in Tight encoding (TightVNC-specific). The "gradient" filter often helps to improve data compression ratios, but may slow down the server performance. Please note that this filter is never used when a client enables JPEG compression in the Tight encoding.
-desktop name: Set VNC desktop name ("x11" by default).
-alwaysshared: Always treat new clients as shared, never disconnect existing client on a new client connection.
-nevershared: Never treat new clients as shared, do not allow several simultaneous client connections.
-dontdisconnect: Don't disconnect existing clients when a new non-shared connection comes in, refuse new connection instead.
-viewonly: Don't accept keboard and pointer events from clients. All clients will be able to see the desktop but won't be able to control it.
-localhost: Only allow loopback connections from localhost. This option is useful in conjunction with SSH tunneling.
-interface ipaddr: Listen for client connections only on the network interface with given ipaddr.
-inetd: Xvnc is launched by inetd. This option causes Xvnc to redirect network input/output to stdin/stdout.
-compatiblekbd: Set META and ALT keys to the same X modifier flag, as in the original version of Xvnc by AT&T labs (TightVNC-specific).

BUGS

There are many security problems in current Xvnc implementation. It's recommended to restrict network access to Xvnc servers from untrusted network adresses. Probably, the best way to secure Xvnc server is to allow only loopback connections from the server machine (the -localhost option) and to use SSH tunneling for remote access to the Xvnc server. For details on SSH tunneling, see <URL:http://www.uk.research.att.com/vnc/sshvnc.html> .

AUTHORS

Original VNC was developed in AT&T Laboratories Cambridge. TightVNC additions were implemented by Constantin Kaplinsky. Many other people participated in development, testing and support.