The Next Generation display numbers

Michael Ossmann michael.ossmann "at"
Wed, 20 Mar 2002 16:57:24 +0000

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.  :-/

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 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 current system only makes good sense on one platform, and it doesn't

> 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.

> 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.

Mike Ossmann, Tarantella/UNIX Engineer/Instructor
Alternative Technology, Inc.
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