Display on vnc client over a network

display-vnc : Display on vnc client over a network

display-vnc: [-bind=<iface>] [-client=<host>] [-copyrect=no|always]
             [-corre=no] [-deskname=no] [-desksize=no] [-display=<dpy>]
             [-gii=no] [-hextile=no] [-kold] [-passwd=<file>]
             [-physz=<sizex>,<sizey>[dpi]] [-rre=no]
             [-server[=<dpy>|stdio]] [-stdio] [-tight=no] [-title=<title>]
             [-viewonly] [-viewpw=<file>] [-wmvi=no] [-zlib=<level>|no]
             [-zlibhex=<level>|no] [-zrle=<level>|no]

Provides a linear framebuffer in main memory. A vnc client that connects gets to see a copy of this framebuffer. The protocol used is the remote framebuffer protocol, or the RFB protocol for short.

The supported RFB protocol versions are 3.3, 3.7 and 3.8.

'-bind=<iface>'

Bind the server socket to the specific iface, e.g. 127.0.0.1 in case display-vnc should only accept connections from an ssh tunnel.

'-client=<host>'

Make a connection to host, instead of waiting for clients to connect. A vnc viewer in listening mode is expected to be found on host.

'-copyrect=no|always'

Controls when the CopyRect encoding is used. Select no to disable it completely, and always to enable it when suitable even if there is support for some other encoding the client has preferred. The default is to only use the CopyRect encoding if it is the most preferred encoding available.

'-corre=no'

Disables the CoRRE encoding.

'-deskname=no'

Disables the DesktopName pseudo-encoding.

'-desksize=no'

Disables the DesktopSize pseudo-encoding.

'-display=<dpy>'

The display number clients should connect to. Display number 0 is equivalent to tcp port 5900.

If the -client option is also given, this is instead the display number this server connects to, and display number 0 is equivalent to tcp port 5500 in that case.

'-gii=no'

Disables the gii pseudo-encoding.

'-hextile=no'

Disables the hextile encoding.

'-kold'

Kill On Last Disconnect. This option ends the application when the last client disconnects. It can be useful in conjunction with the -client, -stdio and -server=stdio options so that the application does not linger without any user feedback.

'-passwd=<file>'

The vnc client has to successfully encrypt a random challenge with the password stated on the first line of file in order to connect. In the password, only the eight first characters and the seven least significant bits of every character are used in the authentication. If this password is given, the client is allowed to send input events such as keys and pointer movements to the application. However, this allowance may be overridden with the -viewonly option. See the options -viewonly and -viewpw for comparison.

'-physz=<sizex>,<sizey>[dpi]'

This option will provide a physical screen size for applications which wish to remain resolution independent. sizex,:p:sizey are the x,y size of the screen in millimeters, unless the optional 'dpi' string is affixed, in which case, they represent resolution in dots-per-inch.

'-rre=no'

Disables the RRE encoding.

'-server[=<dpy>|stdio]'

To run both a server and open a client at the same time, but with different display numbers, the server display number can be specified using -server=<dpy>. If no argument is given, the display number is collected for the -display option. Use -display=stdio to accept connections from the stdin file handle, which is suitable for serving a GGI application as an inetd(8) wait type service (see the example below). The -server=stdio option is incompatible with the -stdio option.

'-stdio'

Talk the RFB protocol on stdin/stdout instead of waiting for clients to connect. Suitable for serving a GGI application as an inetd(8) nowait type service (see the example below). One requirement though, is that the served GGI application does not "chatter" on stdout and/or stderr. The -stdio option is incompatible with the -server=stdio option.

'-tight=no'

Disables the Tight encoding.

'-title=<title>'

The title clients should use on their windows. If this option is not specified, the default is "GGI on vnc".

'-viewonly'

If this option is given, no client is allowed to send input events such as keys and pointer movements to the application. If the -passwd option has also been given, the given password is effectively reduced to a -viewpw password. This option is intended for use together with e.g. the display-multi(7) target.

'-viewpw=<file>'

The vnc client has to successfully encrypt a random challenge with the password stated on the first line of file in order to connect. In the password, only the eight first characters and the seven least significant bits of every character are used in the authentication. If this password is given, the client is not allowed to send input events such as keys and pointer movements to the application. See the options -passwd and -viewonly for comparison.

'-wmvi=no'

Disables the WMVi pseudo-encoding.

'-zlib=<level>|no'

Specify the compression level to use for the Zlib encoding. 0 for no compression and 9 for maximum compression. Saying no here disables the Zlib encoding. If the option isn't specified, a default compromize between speed and compression is selected.

'-zlibhex=<level>|no'

Specify the compression level to use for the ZlibHex encoding. 0 for no compression and 9 for maximum compression. Saying no here disables the ZlibHex encoding. If the option isn't specified, a default compromize between speed and compression is selected.

'-zrle=<level>|no'

Specify the compression level to use for the ZRLE encoding. 0 for no compression and 9 for maximum compression. Saying no here disables the ZRLE encoding. If the option isn't specified, a default compromize between speed and compression is selected.

• Raw, CopyRect, RRE, CoRRE, Hextile, Tight, Zlib, ZlibHex and ZRLE encodings. The CopyRect encoding is only used for panning.
• DesktopName, DesktopSize, GII and WMVi pseudo-encodings.
• Multiple simultaneous clients (shared session).
• DirectBuffer always available, including tidy buffer mode (see ggiSetFlags(3)).
• Multiple frames always available.
• Panning always available.
• Unaccelerated.

To launch a GGI application for each connection made to a TCP port, you may use inetd(8). Just add a line like this to '/etc/inetd.conf':

vnc stream tcp nowait nobody /path/to/app app -t vnc:-stdio:-kold

You also need to define what port the service 'vnc' should use in the file '/etc/services':

vnc            5900/tcp

After you make inetd(8) reread its configuration (e.g. send the -HUP signal to it), you should be able to run the application with a VNC viewer of your choice.

If you instead want to have all subsequent connections share one application instance, change the line in '/etc/inetd.conf' to:

vnc stream tcp wait nobody /path/to/app app -t vnc:-server=stdio:-kold

The Tight encoding uses the jpeg library from the Independent JPEG Group.

• If the application does not give control to libgii with regular intervals (i.e. giiEventRead(3), giiEventPoll(3) or some wrapper that in turn calls one of these functions) this display target will not work, or at least not work well.
• For the Tight encoding there are a few tunables left. 1) The "weight" of the different subencodings needs to be tuned. E.g. the gradient filter subencoding is never used, even if it should be very good on "blocky" data. 2) The jpeg quality selection could probably also be better tuned. 3) The client should be able to select the zlib compression level.
• Special keys (i.e. shift, escape, etc) needs to be converted.