Question about vncviewer frame buffer update requests

[James Weatherall]

Sanjeev,

Please see the RFB protocol document
(http://www.realvnc.com/docs/rfbproto.pdf) for complete details of the RFB
protocol.  All standard versions of VNC as provided by RealVNC Ltd.
(http://www.realvnc.com/download.html) implement RFB.

In short - RFB is adaptive to network bandwidth and no, updates won't go
missing if a particular viewer is running over a slow link.  RFB servers
will never send multiple updates for a single update request.

Wez @ RealVNC Ltd.


-----Original Message-----
From: vnc-list-admin "at" realvnc.com [mailto:vnc-list-admin "at" realvnc.com] On
Behalf Of Sood, Sanjeev
Sent: 31 March 2005 20:04
To: vnc-list "at" realvnc.com
Subject: Question about vncviewer frame buffer update requests


I am new to RFB protocol and trying to understand the protocol. I have
questions regarding the frame buffer update requests in your implementation.



1.	My understanding is that RFB Frame Buffer Requests are purely
driven by the clients. Is that the case with the RealVnc viewer & server
implementation?
2.	When does the viewer request the update and how often does it do
it? Does it poll at some rate, is it tunable, or is it adaptive to the
network bandwidth?
3.	If Xvncserver does not send any updates without clients asking
for it, could client possibly loose some screen full of data if its request
does not arrive in time before the screen changes? E.g. if client types in
ls -lR command to recursively traverse the root directory, there can be lot
of scrolling and client may miss data until his next request arrives.
4.	What if there are two viewers connected to same session, would
screen buffer change caused by one viewer be sent to both viewers or only
when the other viewer asks for it?
5.	How would the realVNC viewer react if a RFB server sends it
multiple updates responses for one request (e.g. to deal with the scrolling
case above or when 2nd client to a session causes some change in the
buffer)? Is it a stateless client or does it track request & responses?



I will really appreciate any help and guidance. Thank you very much,

-Sanjeev Sood
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