Using Virtual Network Computing
VNC system consists of client, server and communication protocol. VNC server is the application installed on a machine to allow sharing of its screen. The application passively gives access rights to the client to control it .The VNC client is the program that watches, control and interacts withserver. The two components must be connected to a network to allow communication. To start VNC, one needs a server and then connects to viewer via the internet. It needs platforms be installed then configured using TCP/IP connection.
Technology underlying the VNC system is protocol for remote access to graphical user Interfaces. It is a very simple, based on one graphic primitive from server to client and event messages from client to server. It works at frame buffer level and therefore applies to all operating systems and applications even to other devices with some communication link. Protocol operate over any reliable transport such as TCP/IP.Alternatively a browser can connect to a server and server can connect to a viewer that in this case is the listening port. One advantage of listening mode is that the server site does not have to configure its firewall to allow access on port. Most of the operation are on the viewer necessitating operator to be more knowledgeable, the server do not needs computer expertise.
The server sends small rectangles of frame buffer to the client .Protocol for communication used by VNC consumes a lot of bandwith. So various methods have been devised to reduce communication overhead. The VNC protocol allows the client and server to negotiate which is supported by all clients and server, is the raw encoding where pixel data is sent in the left to right scan line order and offer the original full screen to be transmitted, rectangles that change are the ones which are transferred. This encoding works very well if only a small portion of the screen changes from one frame to the next but bandwidth demands get very high if a lot of pixels change at the same time such as when scrolling a window or viewing-full screen video.
Using VNC over the internet works well if the user has a broadband connection at both ends. However, it may require advanced NAT, firewall and router configuration such as port forwarding in order for the connection to go through. Some users may choose to a virtual private network application to make usage over the internet much easier. Alternatively a vnc connection can be established as LAN connection if VPN is utilized as proxy.
Xvnc is the UNIX vnc server which is based on standard x series. To applications Xvnc is an x „server‟ and to remote vnc users it is vnc server. Applications can display themselves on Xvnc as if it were normal x display, but they will appear on any connected vnc viewer rather than on physical screen, keyboard and mouse can be set up and run the vnc server as a service , then the screen, keyboard and mouse can be removed and machine stored in an out of the way location.
In addition, the display that is served by VNC is not necessarily the same display seen by a user on the server. On Unix/Linux computers that support multiple simultaneous x111 sessions, vnc may be set to serve a particular existing x11 session, or start one of its own. It is also possible to run multiple vnc sessions from the same computer .On windows the vnc session served is always the current user session.
VNC is commonly used as a cross platform remote desktop system.For example Apple remote desktop for Mac Os interoperates with VNC and will connect to Linux users‟ current desktop if it is served with Xii VNC with tight vnc .From Linux tight vnc will connect to mac OS x session by Apple remote desktop if the vnc option is enabled, or to a vnc server running on windows.
The end point which the user interact with is client or viewer. The other point where changes to the frame buffer originate and operations happen is the server.VNC is truly a thin client system.