[Qemu-devel] Shared VNC sessions

[Qemu-devel] Shared VNC sessions

[Felipe Sanchez]

Hi, in older versions of the RFB patch it was possible to connect multiple 
VNC clients to the VNC framebuffer. With the current VNC support if I have 
one connected client then any other trying to connect will block until the 
first one disconnects.

After a quick look at vnc.c it seems that the incoming connections are 
handled via qemu's fd_handler function which I'm guessing is where the 
blocking takes place, but I'm not really familiar with qemu's code so any 
help would be greatly appreciated  :-)

Also: Does qemu's current VNC implementation support tight encoding?

Re: [Qemu-devel] Shared VNC sessions

[Daniel P. Berrange]

On Thu, Nov 01, 2007 at 03:49:42PM -0600, Felipe Sanchez wrote:
> 
> 
> Hi, in older versions of the RFB patch it was possible to connect multiple 
> VNC clients to the VNC framebuffer. With the current VNC support if I have 
> one connected client then any other trying to connect will block until the 
> first one disconnects.

That is correct. I had a patch floating around somewhere to immediately
drop the second connection instead of making it block forever, so at least
client don't hang.

> After a quick look at vnc.c it seems that the incoming connections are 
> handled via qemu's fd_handler function which I'm guessing is where the 
> blocking takes place, but I'm not really familiar with qemu's code so any 
> help would be greatly appreciated  :-)

The blocking isn't really anything todo with the fd handlers - the event
loop can handle this kind of thing just fine. The problem is that the
VNC server state is only capable of tracking dirty region updates for
a single client at once. To support multiple clients will require some
significant refactoring of the server state. Not impossible, but not a
quick fix either. It just needs someone motivated enough to poke at it....

> Also: Does qemu's current VNC implementation support tight encoding?

No. Raw or hextile.

Dan.
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