libvncserver-common Mailing List for LibVNCServer (Page 56)

Hi,

On Mon, 13 Sep 2004, Jason Mawdsley wrote:
> I am pretty sure that the VNC protocol has no built in encryption or
> security is this correct?

Correct.

> Are there any plans of wrapping a SSL tunnel around the communications
> channel?

I don't know yet what others did. I was told RealVNC and also Ultr@VNC
have secure tunnels, but did not have the time to check that. It sure
would be good to support a standard.

> Is the only way of securing the communications at present to create an
> SSL tunnel that the client will connect to?

Up to now, yes.

Ciao,
Dscho

Hi,

On Mon, 13 Sep 2004, Jason Mawdsley wrote:
> Is it possible to configure the server to only use a specific protocol?

Right now it is only possible by writing a NewClientHook which sets
preferredEncoding.

> If that is possible, what protocol is the lightest on CPU usage?

That depends: if your network layer is not heavy on the CPU, raw is the
lightest. RRE is probably the next best: If you measure performance, could
you please send me the data so I can include it on the web page?

Ciao,
Dscho

Hi all-

I have a few questions about VNC security. ;)

I am pretty sure that the VNC protocol has no built in encryption or
security is this correct?

Are there any plans of wrapping a SSL tunnel around the communications
channel?

Is the only way of securing the communications at present to create an
SSL tunnel that the client will connect to?


Thanks in advance,

Jason

Hi all-

Is it possible to configure the server to only use a specific protocol?
For example, only hextile or the raw protocol.=20

If that is possible, what protocol is the lightest on CPU usage?


Thanks in advance,

Jason

Hi,

On Tue, 7 Sep 2004, Jason Mawdsley wrote:

> I am looking for a VGA font to use when displaying a BIOS screen. The
> default font with the library looks ok, but doesn't display all the
> special graphic characters( they appear as black squares ).

Do you mean default8x16?

> Any one have any good fonts that include the graphic characters?

Find a consolefont (Linux) and convert it with consolefont2c.pl...

Ciao,
Dscho

Hi,

On Tue, 7 Sep 2004, Jason Mawdsley wrote:

>
> > - the problem occurs only sometimes?
>
> Yes, I guess it is a timing condition. It only occurs if clients are
> connected.

Sounds sensible.

> > - do you use the pthreaded version?
>
> Yes I do.

I do not have much experience with the threaded model.

> > I don't really understand it, because in the code rfbScreeCleanup()
> > really just removes all clients...
>
> Doesn't it also free the resources as well? Perhaps I should forcefully
> disconnect all the clients first?

That should be an option. I do not really understand why there is a call
to rfbWriteExact anyway, because the client is just removed in Cleanup.
The only idea I have about this: It is not really a warning, only a
notification: Another thread could be waiting to write something, while
the cleanup thread blocks it. Then, the other thread is allowed to
continue, but the socket is to be closed and the interrupt happens,
because there is nothing to read from the just closed socket.

Ciao,
Dscho

Hi all-

I am looking for a VGA font to use when displaying a BIOS screen. The
default font with the library looks ok, but doesn't display all the
special graphic characters( they appear as black squares ).

The VGA font in one of the packages has the special characters, but
doesn't look as good.

Any one have any good fonts that include the graphic characters?


Thanks,=20
Jason

> Couple of questions:
>=20
> - why do you usleep()?


I usleep() because I am not the only process on the device. The other
processes cannot starve.

> - the problem occurs only sometimes?

Yes, I guess it is a timing condition. It only occurs if clients are
connected.

> - do you use the pthreaded version?

Yes I do.

> I don't really understand it, because in the code rfbScreeCleanup()
really
> just removes all clients...

Doesn't it also free the resources as well? Perhaps I should forcefully
disconnect all the clients first?


Thanks,
Jason


=20

Hi,

On Wed, 1 Sep 2004, Jason Mawdsley wrote:

> Is there away to stop the server cleanly on a SIGINT?
>
> I occasionally see the following traces.
>
> 01/09/2004 19:56:13 WriteExact: select: Interrupted system call
> 01/09/2004 19:56:13 rfbSendUpdateBuf: write: Interrupted system call

as far as I am concerned: I think this is as cleanly as you can exit from
a SIGINT. It says that the system call was interrupted, which is true.
After that, it should exit (more or less) gracefully.

Please correct me if I'm wrong.

Ciao,
Dscho

Is there away to stop the server cleanly on a SIGINT?

I occasionally see the following traces.

01/09/2004 19:56:13 WriteExact: select: Interrupted system call
01/09/2004 19:56:13 rfbSendUpdateBuf: write: Interrupted system call


Thanks in advance,
Jason

Hi,

I plan to clean up the API a little bit. While investigating other things
I found a couple of functions which are exported, but do not have one of
the prefixes "rfb", "zrle" and "sra". I want to prefix them. At the same
time I realized that a few variables of the structs rfbScreenInfo and
rfbClientRec have a prefix "rfb", while the majority does not.

If nobody has good reasons against that, I will commit the changes either
today or tomorrow. I think in order to stabilize the API enough to justify
version 1.0 along with the default to a shared library, we have to do
that.

Unfortunately, this is going to break a few compiles. As a rule of thumb:
If the compile fails because of a function, prefix it with "rfb" (or
change "vnc" to "rfb"). If it is a variable inside a structure and has a
prefix "rfb", remove the prefix.

Ciao,
Dscho

Hi,

On Thu, 19 Aug 2004, Jason Mawdsley wrote:
> 1) How does the server react to the back pressure of the network? Is it
> possible for me to know when the VNC client requests updates? I hope
> this will allow me to scale down my CPU usage when dealing with clients
> on slow connections.

Currently, there is no straight forward way to know where an update
request came from (the client or your backend?). However, if you know you
have not modified a region, the update requests obviously only can come
from the client.

Also, there is no way yet to time the connection, i.e. to measure how long
it takes in terms of bytes/second to deliver data to the client.

> 2) How does the server handle sending out the updates? IE when I call
> MarkRectAsModified are the changes immediately sent? Or are they queued
> until the client asks for them?

They are queued. The function rfbProcessEvents handles the sending.

> 3) If the requests are queued, does the server automatically throw them
> out if told of another change affecting the same region?

It is only the dimensions of the rectangles which are queued. And those
are merged when there are still unsent rectangles.

> 4) What are some ways to increase performance? As stated, I have a
> 400mhz ARM, on that I am running Linux, and various other applications.
> Ideally, I don't want to run higher then 50 %( odd spikes above are OK)
> while still maintaining a good user experience.

The easiest way to increase performance probably is to restrict the
encodings. Tight, ZRLE and ZLib encodings are quite expensive in terms of
CPU power, but Raw and RRE are not.

> 5) Has any detailed performance analysis been done on the library? Has
> the low hanging fruit already been plucked? ;)

I am quite certain that there are performance bottlenecks. I did no
analysis myself, and I am not aware of others either. The best way IMHO
would be to use OProfile on a Linux host to measure where the most time is
spent, and then decide if that is 1) in LibVNCServer, and 2) feasible to
improve the performance in that function.

Could be some interesting work there, right?

Ciao,
Dscho

Hi all-

I am writing a lightweight VNC server that will run on a 400 MHz Intel
ARM processor.

The current branch I am using 0.6.

I have a few questions about performance, and performance tuning.

1) How does the server react to the back pressure of the network? Is it
possible for me to know when the VNC client requests updates? I hope
this will allow me to scale down my CPU usage when dealing with clients
on slow connections.

2) How does the server handle sending out the updates? IE when I call
MarkRectAsModified are the changes immediately sent? Or are they queued
until the client asks for them?

3) If the requests are queued, does the server automatically throw them
out if told of another change affecting the same region?

4) What are some ways to increase performance? As stated, I have a
400mhz ARM, on that I am running Linux, and various other applications.
Ideally, I don't want to run higher then 50 %( odd spikes above are OK)
while still maintaining a good user experience.

5) Has any detailed performance analysis been done on the library? Has
the low hanging fruit already been plucked? ;)



Thanks for your time,

Jason Mawdsley
Software Designer
Macadamian Technologies

Dear Open Source developer

I am doing a research project on "Fun and Software Development" in which I kindly invite you to participate.
You will find the online survey under http://fasd.ethz.ch/qsf/. The questionnaire consists of 53 questions and you will need about 15 minutes to complete it.

With the FASD project (Fun and Software Development) we want to define the motivational significance of fun when software developers decide to engage in Open Source projects. What is special about our research project is that a similar survey is planned with software developers in commercial firms. This procedure allows the immediate comparison between the involved individuals and the conditions of production of these two development models. Thus we hope to obtain substantial new insights to the phenomenon of Open Source Development.


With many thanks for your participation,
Benno Luthiger


PS:
The results of the survey will be published under http://www.isu.unizh.ch/fuehrung/blprojects/FASD/.
We have set up the mailing list fa...@we... for this study. Please see http://fasd.ethz.ch/qsf/mailinglist_en.html for registration to this mailing list.

_______________________________________________________________________

Benno Luthiger
Swiss Federal Institute of Technology Zurich
8092 Zurich

Mail: benno.luthiger(at)id.ethz.ch
_______________________________________________________________________

Hi,

On Wed, 21 Jan 2004, Juan Jose Costello Levien wrote:
> Hello, I have tried the GCC command line inside Cygwin, and worked
> perfectly! :-)
> Now I am writing my own makefile for my project, and typed this:
>
> #MAKEFILE VNCServer Program
> main:
>  gcc -lvncserver -L"/usr/local/lib" -o main main.c
>
> and gcc complains with this output:
> $ make
> gcc -lvncserver -L"/usr/local/lib" -o main main.c
> /cygdrive/c/DOCUME~1/ADMINI~1/LOCALS~1/Temp/ccUAU5JE.o(.text+0x55):main.c:
> undefined reference to `_rfbGetScreen'
> [...]

The problem is that you have to put "-lvncserver" after "main.c". I only
had this kind of problem with cygwin, however.

> The difference between the command line i put and yours about gcc is the
> parameters in "$" - "$(libvncserver-config --cflags)" and
> "$(libvncserver-config --libs)", which I don't know what they are. Maybe
> they are from a script I suppose...

libvncserver-config is a script, which exists in the LibVNCServer
directory. It also gets installed by "make install".

The purpose of this script is to ensure you have set all flags and
libraries correctly, because the library can make use of libjpeg and libz,
but then you have to link them in.

The expression "$(libvncserver-config --cflags)" executes the program
"libvncserver-config" with parameter "--cflags" and then puts the output
on the command line instead of this expression. This only works with bash;
normally you would write `libvncserver-config --cflags` in another shell.
I prefer the first form, because you can nest it.

Ciao,
Dscho

Hello all,

I just checked in progressive updating:

When sending a framebuffer update, do not send all, but only a slice of
a certain height at a time. This should make it easier to interact with a
rapidly changing window with x11vnc.

It works by specifying "-progressive height" as a command line option,
where height is the height of the slice in pixels.

Ciao,
Dscho

Hello, I am writing to you because I tried to compile (or install) the LibVNCServer
libraries for use in Dev-C++ environment. Dev-C++ has the MingW compiler,
so I don't know if it is ok. The thing is that this is my first attempt to
compile UNIX sources in Windows (I don't know how to run the configure script
to generate the makefile). Maybe to rename configure as a batch file, but
I looked inside and the code has nothing to do with DOS batch! :)
If you please can give me some advice, information to read about (or if you
already made it), I will be glad.

Thanks.

Juan





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