Virtual Network Computing
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Presentation Transcript
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?
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
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
Where to get VNC? • AT&T Laboratories, Cambridge UK http://www.uk.research.att.com/vnc/ • 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
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
Quickstart use of VNC • Prerequisites • You should be comfortable with the client/server concepts of the X-windows environment • If not, review “Introduction to X windows” • http://www.strath.ac.uk:80/CC/Courses/oldXC/xc.html • 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
Installation of VNC Software • Download site • http://www.uk.research.att.com/vnc/download.html • 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
VNC Software components • VNC has two major software components Remote vncserver Local vncviewer
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
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
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 “telnet” to login to a SUN UNIX system % telnet armstrong.cis.rit.edu • Make sure remote machine is a SUN platform % uname -a SunOS armstrong 5.7 ...
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 • 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
PC/MAC accessing UNIX(starting the server) • Start the server software on the UNIX side % vncserver New 'X' desktop is armstrong:1 Starting app... in ~rvrpci/.vnc/xstartup Log file is ~rvrpci/.vnc/armstrong:1.log
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
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
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)
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
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
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
Other means of VNC access • Java-enabled browser can access any vncserver • For example, access to armstrong:1 http://armstrong:5801 http://armstrong.cis.rit.edu:5801 • Or access to armstrong:2 http://armstrong:5802 http://armstrong.cis.rit.edu:5802 • Successful connection will be followed by VNC password authentication
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>
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>
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”
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
