The Next Generation display numbers

"Beerse, Corné" cbeerse "at"
Thu, 21 Mar 2002 13:50:41 +0000

> -----Original Message-----
> On Wed, Mar 20, 2002 at 10:38:40AM -0500, Grant McDorman wrote:
> >
> > The problem is that VNC, on *nix systems, will always use a display
> > number for access by applications. If one drops the display 
> number for
> > the VNC client connections, then we'll have *two* unrelated IDs for
> > the VNC server - the display number, and the VNC ID, whatever that
> > might be (port perhaps?).
> We already have that.  A typical Xvnc listens for X apps on 
> :1 and also
> listens for VNC clients on :1, where :1 and :1 are two completely
> different things.  :-/

Not that hard: The X number is the ofset from 6000, the vnc number is the
ofset from 5900. However this is only the default

> It's even possible, though rare, to have Xvnc use completely different
> display numbers for X and RFB, which could be incredibly confusing to
> someone who doesn't understand the difference between :1 and :1.  And
> the system breaks down completely if you have 100+ displays.

It's not that rare, it is used with the -init option.

> It would be a lot less confusing if all VNC implementations used a
> single port for RFB.  Xvnc would still have an X display number, but
> anyone using X can be expected to figure that out.

The X number is only to be used in the X protocol. How would you find your
vncserver if there are more than one running on the machine, all using the
same port?

For the M$Windows users, you have this 1 rfb port: 5900. Not hard if you can
only run 1 server. 

> The current system only makes good sense on one platform, and 
> it doesn't
> scale.

The more I think about it, the more I like the current settings. Only the
viewers lack the option to control the port used, it now has to be set with
odd display numbers.

> > I agree it doesn't make much sense in the Windows-only 
> world; however,
> > when connecting to *nix systems (from any system) it does 
> make sense,
> > and (in my opinion) should not be removed.
> In a VNC implementation with a single port serving multiple displays,
> each display would still need some kind of identifier, and it 
> would make
> sense for Xvnc to continue to use the X display number for 
> that purpose.
> It would even work with display numbers > 99, which would be 
> refreshing.

X11 has problems using display numbers over 99 since only port 6000 - 6099
are reserved for X11. With that in mind, a lot of software uses 8 bits
numbers. Take that signed and the displays over 127 will mangle with Xvnc.
Either display :155 or :156 crashes straight into your vncserver port....

> > Perhaps what we need is a way to explicitly specify the VNC 
> port (the
> > 580x/590x) on both the client and server. Connections to non-*nix
> > systems could then use that.
> That would be nice too.  Xvnc currently has command line options with
> which you can specify either port number or display number.  
> It would be
> nice if other implementations had that feature as well.

The java applet has, check the html code you get on port 5800.

> >

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