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Frequently Asked VNC QuestionsThis isn't intended to be an introduction to VNC - have a look at the Getting Started page first.This list is being updated regularly, so, particularly if you are reading a local or mirrored copy, it's worth checking the original from time to time. The archives of the mailing list are also available, and they can be a good source of help - try searching them here. Historical Note: With the release of 3.3.2 we have moved
some of the old questions into the Old FAQ page
because they should not apply to recent versions. As with most software,
it's worth checking to make sure you've got the lastest version.
The FAQ is divided into the following sections:
Installation errors, startup problems, basic communication difficulties, etc Mouse problems, display issues etc. How can I make VNC faster/more secure/run on my platform? Building VNC for yourself. Q. Where can I get VNC?The latest versions of VNC and this documentation are
always available from the AT&T Laboratories Cambridge web site at http://www.uk.research.att.com/vnc.
In addition, various add-ons, extras, and ports to other platforms can
be found on the contribs page.
Q. I thought this was something to do with ORL? What's the Olivetti/Oracle link here?In January 1999, AT&T
acquired ORL, the Olivetti Research Laboratory founded 12 years earlier,
and recently jointly funded by Oracle,
to create AT&T Laboratories Cambridge.
Q. I downloaded the .EXE files and they don't work!Netscape seems to have a nasty habit of sticking a
.EXE extension on a file when it thinks it knows what type it is.
When you fill in the download form you specify the type of compression
you would like to use, and this does not include .EXE, so if the
thing you downloaded has that extension, change it to whatever you requested
(usually .tgz) and then unpack the files using an appropriate decoder.
Q. I unpacked the files on NT and ran SETUP.EXE but nothing happens.Make sure you have NT service pack 3 installed.
It appears that the InstallShield system we use won't work without it.
Q. WinVNC causes a 'Blue Screen of Death' on NT!Again, make sure you have Service Pack 3 or later.
If this happens it is usually due to bugs in Service Pack 1. Also
note the Service Packs' warning that if you add or change components on
your system you should reapply the service pack. If this doesn't fix it,
check for updates to your network and graphics drivers. VNC makes very
extensive use of both your video system and your network, and has a tendency
to find any bugs in either of them! There may well be bugs in WinVNC, but
we know of people running it without problems on hundreds of machines,
so please check other parts of your system before assuming it's directly
a WinVNC problem.
Q. How do I set up a Windows 95/98 machine so that I can dial into it directly and view it using VNC?You need to install your modem from the control panel
if you haven't already, and you need to set up the dialup networking server
on your server machine. (This is included with Win98 and NT4. On
Win95 it is in the Plus! pack, but you need to get an update to version
1.3 or later from Microsoft's site. At the time of writing it can be found
here.)
You can enable the dialup server from the 'Connections' menu of the dial-up
networking window. If it isn't there, or if you've updated the dialup networking
as mentioned above, you need to install it using the Windows Setup section
of 'Add/Remove Programs' in the control panel. When it's running and you've
dialled in, the server machine should have an IP address something like
192.168.55.1 as seen from the viewer - you can find this out by hovering
over the VNC server icon, using 'netstat -r', or running winipcfg. You
should then be able to connect to, for example, 192.168.55.1:0.
Q. I ran the vncserver program and got a 'No such file or directory' message.Vncserver is a Perl script and so the first line has
to point to the place where Perl is installed. On Linux this will generally
be /usr/bin/perl, on other platfroms it's more likely to be /usr/local/bin/perl.
Edit the line to point to the right place and it should work.
Q. I ran the vncserver program and got a 'Number found where operator expected', 'prototype mismatch' or 'out of memory' message.Note: This problem should be fixed in 3.3.2R3 and later.
This is a Perl error, and happens on platforms where the Perl installation
is not quite correct. We've heard of it particularly on S.u.S.E. linux
and Redhat 5.2. The problem is probably the line in the vncserver script
which says:
eval 'require "sys/socket.ph"';
Your first option is to change this to:
($] >= 5.0) ? eval 'use Socket' :
eval 'require "sys/socket.ph"';
If this doesn't work, particularly on S.u.S.E., you
could try:
eval 'require "linux/socket.ph"';
or check your Perl installation to see if socket.ph
is to be found in another directory.
Q. I started the X server using vncserver, but it dies with a message "Could not open default font 'fixed'. "The 'fixed' font is needed for the server to start
- if it can't find it, you need to specify the correct font path for your
machine in the 'vncserver' script. If you're not sure what the path
should be, type 'xset q' from within a normal X session. One of the
things reported is the font path used by your current X server, which is
generally the right thing to use for Xvnc. On some platforms you
may need to use a colon as a separator in the font path instead of a comma.
If you're on a recent version of Linux but still using VNC version 3.3.1,
you may have compressed fonts which VNC doesn't understand. Either upgrade
or see the Old FAQ.
The VNC server can also get upset if you have directories
on your font path which don't actually exist on your system. Make
sure you remove those. Also note that the Xvnc server, by default, acts
as if it has a resolution of 100dpi. Some RedHat installations, for
example, only install 75dpi fonts, so you may need to install the missing
font RPMs from your distribution or use the -dpi option to Xvnc.
Q. I get errors like "failed to bind listener" and "Failed to establish all listening sockets" in the log file.This is probably due to the permissions on /tmp/.X11-unix. You may well see this if you update to Solaris 2.7, for example. See the section below entitled "Why can I only run vncserver/Xvnc as root?".Q. Vncserver seems to be dying quietly without putting any messages in the log file.Check that the Xvnc process really has died. If so,
then check that your VNC font path (set by uncommenting lines in the vncserver
script) only includes directories which actually exist. The XFree86
code in Xvnc seems to have a problem which causes the server to die quietly
if non-existent directories are searched. You could also modify the
vncserver script to check for and remove non-existent directories. See
Bruce
A. Mah's patch for an example.
Q. My Solaris/HP-UX Xvnc dies with a core dump!There is a bug in XFree86 (on which Xvnc is based)
which makes Solaris servers very unreliable if they have a pixel depth
of 16. Use the -depth option to start your server with a depth of 8 or
24, and you should be fine. We've heard that this can be a
problem with HP-UX as well. Darrell Kindred submitted a
patch which speeds up operation on Alpha machines, and also fixes
this problem.
Q. I connected to my Unix server and I just see a grey desktop with a cursor. Where's my normal X environment?After the vncserver script has started the Xvnc server,
it then runs your ~/.vnc/xstartup script. By default this will try
to start the twm window manager, but if twm isn't on your path, or if you
prefer something else, you can edit xstartup. The log file may also
give you clues about what is happening.
Q. The log file is showing an error message from xrdb / Xlib.By default, the first thing your xstartup script does
is to run xrdb to load your resources. So if the Xvnc server has
not started for any reason, the xrdb is often the first thing to notice
it and print an error. (Though if you're getting a 'command not found'
message, then xrdb is probably not on your path - you need to find where
it is on your system and add it.)
If you get something like 'connection refused' or 'Can't
connect: errno = 111', the Xvnc server probably isn't there. So you
should check whether the Xvnc process is actually running, and whether
there is anything earlier in the log file indicating why it might have
died. By far the most common reason for the server not starting is
that it can't find the 'fixed' font (see above). Other possibilities are
that the server has quietly crashed, or that it is taking a very long time
to start up. The vncserver script has a 3-second delay before running
xstartup, but in extreme cases this may not be enough. Lastly, the
DISPLAY variable used by vncserver is based on the results given by the
'uname - n' command. If your applications cannot resolve this to the right
IP address, perhaps because of funny settings in /etc/hosts, then they
won't be able to connect.
If you get a 'Client is not authorized to connect to
Server' or similar message, there's something wrong with the X authority
setup - perhaps xauth is not on your path? You could try using xhost to
bypass this temporarily, but we wouldn't recomend this as a long-term solution.
There should be some indication in the log file if xauth has failed.
Q. The Java client doesn't work in my browser.Several Java implementations have bugs which upset
the VNC applet. We recommend Internet Explorer 4 - we've had good
results with this on both Windows machines and Macs. Netscape Navigator
3 has a bug which can cause problems; if you get the 'Method setClip not
found' error, try pressing Reload.
Q. My viewer failed to connect to my server!VNC relies on a correctly-configured and operational
TCP/IP network, so please make 100% sure that your TCP/IP setup is right
before you start asking questions on the mailing list. Here are some
things you should check before assuming it's a VNC problem; consult your
local expert if you don't know how to check them:
Q. My X VNC server is working, but I don't see my normal environment. How can I change the Window manager etc?The window manager is started by the ~/.vnc/xstartup script. We use twm, as this is available on almost all Unix platforms. Edit the script if you'd rather replace it with something else. On many platforms you can, as an alternative, just make xstartup a link to whatever script normally starts your X environment.If you want to be more sophisticated, you can specify the -name option to vncserver, and then take different actions in the xstartup script based on the name given. For example: case "$VNCDESKTOP" in kde) startkde & ;; *) xterm -geometry 40x10+40+40 -ls -title "$VNCDESKTOP Desktop" & twm & ;; esac Q. Why can I only run vncserver/Xvnc as root?The most likely reason for this is that Xvnc can't
create the unix domain socket (the path for this unix domain socket is
usually /tmp/.X11-unix/Xn). Try making sure that users can write
to this directory by making it world-writable, i.e. "chmod a+w /tmp/.X11-unix".
Note that to avoid a security loophole the "sticky bit" should also be
set on the directory by doing "chmod o+t /tmp/.X11-unix". If you
don't do this then someone else logged in to the same machine may be able
to intercept the X protocol and thereby access your desktop and snoop on
it, etc. An alternative is to set the Xvnc binary to have the same
permissions as your normal X server, but this may be more of a security
risk.
Q. Can I remote the normal X display of my workstation (display :0) in the same way as the Windows server does?It would be possible to add VNC support to a standard
X server, so that it operated this way, but we have no plans to do so.
It shouldn't be too difficult, if you have the full source code for your
X server. Xvnc is basically XFree86 with the hardware-dependent bits
taken out and VNC put in their place, so it doesn't have drivers for any
graphics cards. You could have a look at the Xvnc source code to see which
bits have been added to the standard XFree86, and make the equivalent changes
on your X server.
We tend to run all our X sessions as VNC sessions and only use the local X server to run the viewer. It's very fast when on the same machine as the server! If you feel that it's overkill to run two X servers on the same machine, you might consider Ganesh Varadarajan's svgalib-based viewer, available from the contribs page. Q. What X Visual does Xvnc use?By default, vncserver will start Xvnc with the same
depth as the current X display, if there is one, or 8 bits deep if there
isn't. We've tried to steer clear of colour maps as much as possible
and normally use "true colour", even when there are only 8 bits per pixel.
Unfortunately some X applications don't cope too well
with an 8 bit TrueColor visual. You can make Xvnc use the more
normal PseudoColor visual by giving a "-cc 3" option to vncserver.
Q. Can I cut and paste between the viewer and the server?VNC supports copying and pasting of ASCII text in both
directions, provided the viewer and server allow it. When the clipboard
changes on the machine running the viewer, the changes are copied to the
server and vice versa. Some notable exceptions:
The code to do copying from the X server to
the viewer didn't make it in the original version 3.3.2. It's back
in 3.3.2R2 and later, so upgrade if you haven't already!
Q. There's a memory leak in Xvnc!This occurs in version 3.3.2r2 and earlier, but is
fixed in 3.3.2r3 and later versions. If you're using an older
distribution you can find a patch for it here.
Q. Can I run the Windows server before anybody has logged in?You can now! Make sure you have a recent WinVNC and
read the section on running WinVNC as a service in the documentation.
Q. Why can't I unlock my NT workstation remotely? Why can't I stop the screensaver remotely? Why doesn't Ctrl-Alt-Del work?Make sure you are running a recent version of VNC,
and that you are running it as a service. From some platforms
you will not be able to type Ctrl-Alt-Del directly, because it will be
caught by the local machine. The Windows viewer, for example, has an
option on its menu to send a Ctrl-Alt-Del to the remote host. In some situations, you will find that something like Ctrl-Alt-Backspace or Ctrl-Alt-<Numeric keypad Del> may work instead.
Screensavers sometimes use a different resolution and so can disconnect you when they stop or
start - see the next question.
Q. When I connect using VNC and then log into my Windows machine, I get disconnected and have to reconnect!Sometimes logging in will involve a change in screen resolution, if the user's display settings are different from the defaults. If this happens, the server will disconnect you and you will need to reconnect to get the new screen size. Just occasionally on NT, the mode seems to change resolution temporarily as you log in, and if WinVNC happens to see this you can also be disconnected, even if the final resolution changes.If the user has set a different display number in their personal WinVNC properties dialog you will also be disconnected. Q. I have troubles sending Ctrl-Alt-Del to a Windows server.
Q. The dead keys don't work on my keyboardThey will soon! It's quite a challenge working
out how to do international keyboard support across different platforms.
We're working on dead keys.
Q. When I start a DOS window, it doesn't display at the remote end.You might also notice the pointer leaving a trail of arrows behind it. This happens when your DOS sessions are full-screen. WinVNC cannot read the display when this happens, but keystrokes should still get through. Press Alt-Enter to switch the DOS box to windowed mode.Q. I can't type into a DOS window or any DOS appsThis derives from the fact that Windows 95 uses BIOS
calls and not Windows messages to get keystrokes within the command prompt.
It should be fixed in version 3.3.1 R19 and later of the WinVNC server,
so if you're using an earlier version, uninstall and upgrade.
Q. The keyboard doesn't work / keys do strange things!There is one common problem which can cause this.
If a modifier key, such as Shift, Ctrl or Alt, is pressed, and the viewer
window then loses focus or dies, the 'key release' message never gets to
the viewer and hence never gets to the remote server. The remote
machine will then think that M is Ctrl-M etc. We have done various
things to reduce the chance of this happening; the viewers release various
modifiers automatically when they lose focus, for example, but it can still
occur and can be confusing when it does. The solution is easy: simply
press and release the modifier key which is stuck. If you don't know
which it is, then try them one at a time.
Q. Most of my Windows apps work fine remotely, but this one doesn't update its window...WinVNC can use a variety of hints to guess when a particular
area of the screen has changed. The most useful is the occurrence
of a WM_PAINT message in an application. Not all applications
use these messages, though; the Windows clock is a good example.
In the registry WinVNC has a list of application names,
and which things to use as update clues. A few standard applications
are set up by the 'Install default registry settings' in the WinVNC section
of the Start Menu; it tells WinVNC to look for timer messages from the
clock, for example. Make sure you install these if you haven't already.
Any other apps you run will appear in the registry, so you can easily tweak
the settings. For more info, see the WinVNC documentation.
Q. WinVNC is putting a huge load on my PC!Firstly, WinVNC should have negligible impact when
nobody is connected to it. It does practically nothing in this state. If
you find that it is running at something close to 100% CPU when there is
a remote connection ,check the Update Handling in the Properties dialog
box. The default settings should be fine in most circumstances. If
you have either (a) Ticked 'Poll Full Screen' or (b) Ticked 'Poll Foreground
Window' or 'Poll Window Under Cursor' without having 'Poll Console
Windows Only' ticked, then the load will be much higher. See also the section below on 'How do I make VNC go faster?'.
Q. WinVNC dies, or causes other applications to die, after a short time when a viewer is connected.Some screen savers, particularly on Windows 95, do
not interoperate well with WinVNC. Try disabling all screen savers
on the machine running the server and see if that fixes it.
Q. My remote Windows display is appearing in a very garbled form.There can be problems with WinVNC being unable to detect
changes to the screen on certain applications, as mentioned in the previous
question, but there should not generally be serious screen corruption.
Make sure you have the latest service packs installed for your OS and experiment
with different video drivers. WinVNC relies on various aspects of
the video card and driver; in particular its ability to BitBlt correctly,
and several users have solved their problems by updating the driver.
Q. I have problems with double-clicks in Windows.By default, mouse button up events are used to signal
to WinVNC that the current window may have changed and should be re-scanned.
This can introduce a delay which results in a double-click being interpreted
by the system as a pair of single clicks. Variations in network
delays can also cause the clicks to be too widely separated when they appear
at the server. Some suggestions:
Q. I'm installing WinVNC as a service on lots of machines, and I get prompted for the password on each one. Can I do this non-interactively?Not directly, but you can by editing the registry before
installing. On a machine which already has WinVNC installed, copy all the
registry settings under
into the same place in the registry of the remote machine, either by hand or using your favourite tool. When WinVNC runs, it will see the password in that section of the registry and will not prompt you to type one in. Another hint that might be useful was sent in by Johannes Norinder. If you run the SETUP program with a -r option, it will create a setup.iss file, probably in your %systemroot% directory. Following installations on similar computer can be started with "setup -s -h1[path to your setup.iss]" and you won't have to answer the questions again! Q. I only have a two-button Windows mouse, and I really need three buttons for X...Get version 3.3.2R10 or later of the Windows viewer.
This allows you to emulate the middle button by pressing both buttons together.
Q. I have a three-button Windows mouse, but the middle button doesn't work.This is almost certainly a problem with your mouse
driver. The Windows VNC viewer recognises standard WM_MBUTTON...
messages and should work with any driver that generates them. Some
drivers, knowing that Windows seldom normally uses the middle button, either
don't recognise it, or map it to something else like a double-click. Try
telling Windows that you have a different type of mouse, (we've had reports
that the Logitech PS/2 Port Mouse is a good one to try) or use the 3-button
emulation mode mentioned above. I think some PS/2 mouse port hardware may
also not recognise the middle button.
Q. My machine doesn't have a DNS entry or static IP address! What address should other people use to connect to my WinVNC server?If your ISP allocates you a dynamic IP address when
you dial in, you will need to give that to the person trying to connect.
On Windows95 machines, after connecting, you can use the winipcfg
program (type it into the Start/Run... box). On NT machines, type
ipconfig
at a command prompt. On linux machines, try hostname -i.
A handy new feature on recent versions of WinVNC causes the IP addresses
of the local machine to be displayed when the mouse hovers over the WinVNC
icon, (if they can be determined at that time).
Of course, if your phone line is now in use you may
need to find some other way of getting this information to the remote person.
I suggest a chat system like AOL Instant Messenger. There are also programs
out there which will automatically create a web page with your current
IP address, which the other person could then read.
Q. Can I get rid of the taskbar icon created by WinVNC?No. Not without changing and recompiling the source
code. We feel that there would be few legitimate uses of VNC where
you would need to conceal its operation. However, there might
be occasions where you would not want the user of the server machine to
be able to adjust the WinVNC settings, password, etc, so versions later
than 3.3.2R3 will include a 'restricted' mode where the icon is still visible,
but the menu options normally available from it will be disabled.
In some situations, particularly on Win95, you may
find that the icon is not displayed. This is not a feature, it's a bug
which we plan to iron out!
Q. Can I set up WinVNC to use my Windows NT password for authentication?Not at present. Partly because there are many
problems with the NT security model, but chiefly because we want to keep
VNC as cross-platform as possible. In the future we may try and make
the code and the protocol more modular so it will be easier to add your
own favourite authentication.
Q. Can I make the Macintosh server start automatically when the machine boots up?Yes, create an alias to VNCServer and put it into the Startup items folder (in your system folder).Q. When I try to set a new password for my Mac server, I hit CHANGE on the web page, but nothing happens. It is trying to bring up the settings.html page, but fails.The http portion of the current server is unstable, sorry. But you can set your settings with AppleScript.Open the AppleScript editor and enter the following tell application "VNCServer"
There are other options you can set, which are all documented in the
directory inside VNCServer (use the AppleScript editor to open the dictionary)
Q. How do I make VNC go faster?We find VNC to be perfectly acceptable as our normal
method of accessing Unix desktops on a daily basis. This is
over a 10 M/bit ethernet on reasonably modern machines, using the X or
Win32 viewer. Because Windows gives us fewer hints about what it's
doing, and because we don't have the source code for Windows, the NT server
has to work harder to find out what's changed, and so a really fast machine
should make a big speed difference. For more information about how
the Windows server works, see the WinVNC documentation.
But if you've been disappointed by the speed of the Windows server, don't
give up. We're improving it gradually, though it'll be a while before
it's as fast as on Unix.
There are several things that can slow any VNC session
down, however, and you may like to consider these if you find it too slow:
Q. Will VNC work through a firewall?It depends on your firewall, and whether you want to
access a server inside your firewall from elsewhere, or a server outside
your firewall from inside.
Generally firewalls are designed to prevent incoming
connections except to certain well-known machines and ports. If you
can configure these to include your VNC server, then you will be able to
access it from anywhere in the world. There is a good argument to
be made for the fact that VNC is less of a security risk than X, so if
your site doesn't allow X in or out it may still allow VNC.
Many modern firewalls will allow outgoing connections
initiated from inside, so you can often access servers on outside machines.
It is straightforward, for example, to recompile the viewer source to include
SOCKS support, or to make other special arrangements. See the contribs
page.
It's a pity that Java within a browser doesn't automatically
use SOCKS if the browser is configured to use it. There's probably
Java SOCKS support out there somewhere...
If your internet access is through a router which does
Network Address Translation, you may be able to configure the router to
redirect particular incoming ports to particular machines. So you could
run WinVNC with a display number of 0 on machine snoopy, and with display
1 on machine woodstock, then set your router to send port 5900 to snoopy
and 5901 to woodstock. See below for information on the other port
numbers used by VNC.
Q. Which TCP/IP ports does VNC use?A VNC server listens on two ports. The exact port numbers
depend on the VNC display number, because a single machine may run multiple
servers. The most important one is 59xx, where xx is the display number.
The VNC protocol itself runs over this port. So for most PC servers, the
port will be 5900, because they use display 0 by default.
In addition, VNC servers normally have a small and
very restricted web server built in, which allows you to connect a browser
to them and use the Java viewer. This runs on port 58xx. Note
that this is the HTTP port used for downloading pages and applets, but
once the applet is running it uses 59xx for VNC just like any other viewer.
The servers can be changed to listen on other ports
if, for any reason, these are not suitable for you. See the server's
documentation
for more details. Most of the viewers, if given a display number
larger than 99, will interpret it as a direct port number and will not
add 5900.
If you are running a viewer in 'listening' mode, where
it accepts connections initiated by the server, it will listen for incoming
VNC on port 5500. It's unlikely that this will apply to you, because
the servers we distribute publicly don't have this facility.
Q. How secure is VNC?Access to your VNC desktop generally allows access
to your whole environment, so security is obviously important. VNC uses
a challenge-response password scheme to make the initial connection, but
after that the data is unencrypted and could, in theory, be watched by
other malicious users, though it's a bit harder to snoop a VNC session
than, say, a telnet, rlogin, or X session. Since VNC runs over a
simple single TCP/IP socket, it is easy to add support for SSL or some
other encryption scheme if this is important to you. Axel Boldt <axel@uni-paderborn.de>
suggests:
SSH allows you to redirect remote TCP/IP ports so that all traffic is strongly encrypted, and this can be combined with VNC: Setting up SSH is pretty straightforward on Unix
machines, but generally harder on Windows. Miroslav Luptak
<Miroslav_Luptak@snt.sk> has
posted detailed information to the mailing list about how he set his
SSH system up on NT. See http://www.uk.research.att.com/vnc/archives/1999-03/0060.html
for details. There is also a free SSH client for Windows available at
http://www.doc.ic.ac.uk/~ci2/ssh.
SSH can also compress the encrypted data - this can be very useful if using VNC over slow links. Another minor issue you should know about if using the Unix viewer to connect via SSH: By default, when the viewer connects to a server on the local machine, it uses the 'raw' pixel encoding because this generally gives better performance for local access. If this 'server' is actually an SSHD redirecting the data to another machine, you probably want to override this using the -hextile option to the viewer, or you will send a lot more data over the network than you need to.
While we're on the subject of security, you should
also be aware that only the first 8 characters of VNC passwords are
significant. This is because the 'getpass' call used in the Unix
server to read a password has this restriction, and the other
platforms have been made compatible with this.
Ray Jones <rjones@pobox.com>
has
built a version of VNC which uses SSLeay public key encryption, and Wolfram
Gloger <wmglo@dent.med.uni-muenchen.de>
has built Xvnc with the TCP Wrapper library, allowing you more control
over which hosts are allowed to connect. See the contribs
page for details.
Q. Are you going to make it more secure?While we do hope eventually to add better security to VNC, there's also a good argument for not doing so. If security is a concern, it can be better to use a single system such as SSH or FreeS/WAN to encrypt all your traffic, rather than relying on the individual packages to do the right thing. Then, if you decide that one system is too easily crackable in a year's time, you can replace it yourself and all of your communications will benefit.Q. Are you planning support for AIX, EPOC,HP-UX, SGI, Win 3.1, or my favourite platform ?We have provided VNC on all the platforms we use here,
and it's difficult to provide binaries for anything we don't have, and
it takes a while to get up to speed on new platforms. Remember that
a viewer is available for any platform which runs Java, though the speed
may vary quite a bit. But for many platforms it should not be difficult
to compile at least the viewer. If anyone tailors the sources for a particular
platform we will happily either incorporate the changes in the main source
distributions or make the patches available from our site. Information
about other people's ports of VNC to a large number of other platforms
can be found on the 'contribs' page.
Q. Would things work better if you compressed the stream?VNC incorporates really quite efficient compression
in the sense that we generally send a tiny fraction of the raw data, probably
something like 1/20 on average. The details are in the protocol spec if
anyone's interested. On a couple of test screen dumps we found that
the Hextile encoding was more efficient than GIF! I don't know whether
this is true in general.
But we haven't done more general encoding after that;
we've tended to the view that (a) it might introduce too much latency and
(b) most modems compress pretty well anyway. We are planning
some zlib-compression experiments in the near future to see how this affects
things. Because different bits of the screen can be sent using different
encodings, the server could, in theory, detect that one bit would be most
efficiently sent as JPEG, while another would be better hextiled.
The question is always how much work it's worth doing
at the server to find this out. To some degree you can control this
already, because the viewers allow you to specify your preferred encoding.
Under X, if your viewer and server are on the same machine the viewer will
use the raw encoding by default, otherwise it will use hextile. You
may find that by selecting different encodings on the command line you
get better performance.
See the suggestions above about using ssh, which also
provides compression.
Q. Have you thought about caching bits of the screen at the viewer end?Yes, that could also be good. You could have an off-screen
cache in the viewer and the server could copy things from there to the
screen. Management of this would add a certain amount of complexity,
though.
Since there is already a CopyRect primitive in VNC,
an alternative approach would be to copy updates from another part of the
screen if they already exist there, rather than resending them. Again,
to make the server find out efficiently when this is worth doing would
be an interesting challenge, and volunteers for the project are welcome!
Q. Can I use VNC over a modem without TCP/IP?Not at present, but there's no reason why it shouldn't,
and we realise that this would be useful. VNC could run over other transports
such as RS232, firewire, USB, modems etc, but at present we rely on TCP/IP.
This means that you can use VNC over anything which supports TCP/IP, so
using it over a modem is just the same as any other network, once you have
Dial-Up Networking set up. If you need to communicate directly between
two machines without going via the internet/intranet, then set up a remote
access server on one and dial in from the other.
We don't, at present, support simple dialup without
TCP, chiefly because it involves writing a lot of code to talk to the modem.
But it's on the 'suggested projects' page, so any
volunteers welcome...
Q. Does VNC have any Y2K (Year 2000) bugs?The WinVNC server and Windows viewer have been tested
on a PC with its date running through the 2000 boundary without any problems,
so unless the underlying OS or BIOS has difficulties, VNC on a PC should
be fine. The VNC part of the X-based Unix VNC server only uses dates
when writing the log files; the logfile entries are timestamped with a
two-digit year, but the format is easy to change if required and the entries
are not intended to be machine-readable. The developers of the XFree86
server on which Xvnc is based state that there are no Y2K problems (see
http://www.xfree86.org/FAQ/). We therefore issue the standard disclaimer:
we believe the VNC code, in its entirety, to be free from Year 2000 problems,
subject to the other components of the systems on which it is running.
Q. How can I install WinVNC on multiple machines?When you run WinVNC for the first time on a machine,
it will prompt you for a password. If you are doing this on
a large number of machines, especially remotely, this can be a nuisance.
The way to bypass this is to make sure that the target machine already
knows the password by putting the encrypted version straight into the registry
before installing. So:
HKEY_CURRENT_USER\Software\ORL\WinVNC3 , or HKEY_USERS\.DEFAULT\Software\ORL\WinVNC3, (if you installed WinVNC as a service) and install them on the target machine using your favourite registry utility. Q. Can I connect multiple users to the same Windows server, and have them each see their own desktop, as with WinFrame, NTrigue, WTS, etc?No. Windows NT has a reasonable concept of multi-user
access, but not where the GUI is concerned. Basically, you can't
do this without access to the source code of Windows, and that's rather
difficult to get hold of! We have successfully run multiple
WinVNC servers on a Windows Terminal Server machine, but they don't update
unless a WTS client is also connected, which rather defeats the purpose.
It may be possible in future to get documentation on the WTS APIs, in which
case we might be able to do something better.
Of course, if your server is Unix-based, then you have
no problem. You can run dozens of VNC servers on a single machine.
Q. Any other tips?Several people have indicated that they have to use
Windows occasionally but prefer to use Unix most of the time, and so want
to access a PC under the desk from the Unix box.
Here's a suggestion: all other things being equal,
I recommend using the Windows box to view the Unix machine rather than
the other way around. This is chiefly because Windows generally works
better as a client than as a server, and also because PC graphics cards
are often better than those in Unix workstations. Remember, you can
create a VNC session of any pixel depth you like. For my day-to-day
work I use a Solaris 16-bit VNC session displayed on my PC. Few of
our Sun machines have more than 8-bit color hardware, but the PC has plenty
of bits to spare.
If you're very anti-Windows you can make your VNC desktop
the same size as the screen and set the taskbar to 'Auto hide' and just
pretend you're on an X terminal, but pop up the Start menu when you have
to use PowerPoint.... The Windows viewer 3.3.2R4 and later has a proper
'full-screen mode', so you don't even need to bother with auto-hide.
Q. You misspelled 'organization' on the download page!No we didn't. We spell it like that in the UK.
Actually, we spell it both ways, but the 's' spelling is more common, despite
what the OED says! Now, as for 'misspelt'...
Q. I'm trying to compile WinVNC and the compiler complains about various missing files!You need to compile using the No_CORBA configuration,
or it will try to include various files which are part of our internal
version only.
Q. I'm having trouble compiling VNC on my platform...Have you checked the contribs
page? Several people have provided hints on how to build VNC on other
platforms. If yours is not listed there, you might at least get some
clues..
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