1. Virtual Network Computing
VNC

2. Outline What is VNC? Why do we need to be familiar with VNC?
Where do we get VNC?
Limitations of VNC?
Other notes about VNC?

3. What is VNC? Virtual Network Computing (VNC)
Remote control system of other computer windowing environments
Allows access to “desktops” of like or different operating systems
Developed by AT&T Laboratories
Freely Available
UNIX
Windows
Mac

4. Why VNC? Freedom to choose your favorite computing environment
And still have access to the more powerful UNIX system
Remote access is made possible to the major platforms
You want to work at home, but you forgot that one critical file at school on the…
Reinforces the concepts of client/server software
Concept foreign to most PC/MAC users
Price is right
Free

5. Where to get VNC? AT&T Laboratories, Cambridge UK
Available for UNIX environment
Requires system administrator privileges
Already installed on the CIS machines
Available for Windows platform
Requires you to download and install on your machine
Available for Mac platform
Available for Java-enabled browsers

6. Limitations of VNC VNC is network resource intensive
High Bandwidth connection = Good situation
Low Bandwidth connection = Bad situation
Filesystems are still separate between different operating systems
Transferring files still requires other mechanisms (e.g. ftp)
Access to non-Unix platforms do not have good multi-user support
PC/MAC lack general concept of several user access

7. Quickstart use of VNC Prerequisites Configurations you will encounter
You should be comfortable with the client/server concepts of the X-windows environment
If not, review “Introduction to X windows”
VNC server and viewer installed on both local and remote machines
Configurations you will encounter
Local PC/MAC accessing remote UNIX system
Local UNIX system accessing remote PC/MAC
Local UNIX system accessing remote UNIX system

8. Installation of VNC Software
Download site
CIS Unix platforms
Already installed by system administrator
PC platform
Download and install as you would other PC software
Mac platform
Download and install as you would other Mac software

9. VNC Software components
VNC has two major software components
Remote
vncserver
Local
vncviewer

10. VNCSERVER Provides the “remote” half of the “remote control” system
Communicates interactions from the remote machine to the local machine
Exports the view of the remote “deskstop” screen environment to a local machine
Imports keyboard and mouse inputs from local machine to remote machine

11. VNCVIEWER Provides the “local” half of the “remote control” system
Communicates interactions between local machine to the remote machine
Imports the view of the remote “deskstop” screen environment to the local machine
Exports keyboard and mouse inputs from local machine to remote machine

12. Local PC/Mac Accessing Remote CIS SUN UNIX System
Prerequisites
Assumes you have a UNIX account on CIS system
Assumes you have downloaded and installed VNC on your local PC/Mac
Use “ssh” to login to a SUN UNIX system
% ssh armstrong.cis.rit.edu
Make sure remote machine is a SUN platform
% uname -a
SunOS armstrong

13. PC/MAC accessing UNIX (starting server for the first time)
Start the server software on the UNIX side for the first time will ask you for a password
% vncserver –depth 24
This password does not need to be the same as your UNIX password
This password is used only during authentication when you connect using VNC
You can change this password using
% vncpasswd

14. PC/MAC accessing UNIX (starting the server)
Start the server software on the UNIX side
% vncserver –depth 24
New 'X' desktop is armstrong:1
Starting app... in ~rvrpci/.vnc/xstartup
Log file is ~rvrpci/.vnc/armstrong:1.log

15. PC/MAC accessing UNIX (meaning of server messages)
Name of exported “virtual desktop window” is armstrong:1
New 'X' desktop is armstrong:1
The specific X-window manager and associated startup applications is specified by the file below (view using text editor)
Starting app... in ~rvrpci/.vnc/xstartup
Any informational or error messages are logged in the file below (view using text editor)
Log file is ~rvrpci/.vnc/armstrong:1.log

16. PC/MAC access UNIX (start the viewer)
Invoke “vncviewer” application
Double click on vncviewer icon or
“Start->Programs->VNC->Run VNCviewer”
You will be prompted for a remote host name to control
e.g. armstrong:1
You will be prompted for a VNC password
If successful, you should get a window with a view

17. PC/MAC accessing UNIX (windows with a view)

18. PC/MAC accessing UNIX (shutting down the server)
% vncserver -kill :1
Killing Xvnc process ID 10733
Above command kills the virtual window, in this case, armstrong:1
If you do not kill the server, but kill the viewer, you can always reconnect from another viewer and pick up where you left off
Frowned upon by the system administrator if abused (SA has prerogative to kill your desktop)

19. UNIX accessing PC/MAC Desktop
Prerequisites
VNC software installed on UNIX and remote PC/MAC
Owner of PC/MAC has given you VNC password
Vncserver running on PC
Start vncviewer
% vncviewer
Enter PC/MAC VNC server name to access
Enter PC/MAC VNC password

20. UNIX accessing PC/MAC Desktop (X-windows with a view)

21. UNIX Desktop to UNIX Desktop Access
Rarely done using VNC because X-windows already provides this capability
VNC only adds overhead
VNC may be used to save desktop environments from session to session
Procedure similar to PC/MAC to UNIX desktop access

22. PC/MAC to PC/MAC Access
Prerequisites similar to PC/MAC to UNIX access
Be careful interfering with someone working on the remote machine
It is possible to disable remote keyboard and mouse
PC to PC access allows
Limited remote troubleshooting of PC system
Multiple viewers to “listen in” on one window

23. Other means of VNC access
Java-enabled browser can access any vncserver
For example, access to armstrong:1
Or access to armstrong:2
Successful connection will be followed by VNC password authentication

24. Browser Access to VNC server

25. When in doubt about vncserver under UNIX…
bean% vncserver -h
usage: vncserver [:<number>]
[-name <desktop-name>] [-depth <depth>]
[-geometry <width>x<height>]
[-pixelformat rgbNNN|bgrNNN]
<Xvnc-options>...
vncserver -kill <X-display>

26. When in doubt about vncviewer under UNIX
bean% vncviewer -h
VNC viewer version 3.3.3r1
usage: vncviewer [<options>] <host>:<display#>
vncviewer [<options>] -listen [<display#>]
<options> are standard Xt options, or:
-shared
-viewonly
-fullscreen
-passwd <passwd-file>
-encodings <encoding-list> (e.g. "raw copyrect")
-bgr233
-owncmap
-truecolour
-depth <depth>

27. Key VNC Options to consider
% vncserver -depth 24
Starts up your server in 24-bit mode color mode
% vncviewer -share -viewonly
First option
Starts up your viewer so that others can also see the server
Useful for having two or more people control the desktop
Second option
Makes sure that you can only see the desktop and not control it
Particularly useful in a group environment when you want only one person to “drive”

28. Customizing your VNC window manager
Edit the following file
~/.vnc/xstartup
Find the line specifying the window manager command
twm & or
ctwm &
Change to your favorite window manager, e.g.
usr/dt/bin/dtwm &

29. Other VNC considerations
Cutting and pasting text information
Supported between remote and local windows
Provides a foundation for CSCW
Computer Supported Cooperative Work
Source code freely available
Other platforms are actively being included
VNC performance can be an issue, but
Beats driving through the snow to school to pick up that one data file