Tuesday, 13 March 2012


A VNC arrangement consists of a client, a server , and a advice protocol

The VNC server is the affairs on the apparatus that shares its screen. The server irenic allows the applicant to booty ascendancy of it.

The VNC applicant (or viewer) is the affairs that watches, controls, and interacts with the server. The applicant controls the server.

The VNC agreement (RFB) is actual simple, based on one clear archaic from server to applicant ("Put a rectangle of pixel abstracts at the defined X,Y position") and accident letters from applicant to server.

In the accustomed adjustment of operation a eyewitness connects to a anchorage on the server (default anchorage 5900). Alternatively a browser can affix to the server (depending on the implementation) (default anchorage 5800). And a server can affix to a eyewitness in "listening mode" on anchorage 5500. One advantage of alert approach is that the server armpit does not accept to configure its firewall to acquiesce admission on anchorage 5900 (or 5800); the onus is on the viewer, which is advantageous if the server armpit has no computer expertise, while the eyewitness user would be accepted to be added knowledgeable.

The server sends baby rectangles of the framebuffer to the client. In its simplest form, the VNC agreement can use a lot of bandwidth, so assorted methods accept been devised to abate the advice overhead. For example, there are assorted encodings (methods to actuate the best able way to alteration these rectangles). The VNC agreement allows the applicant and server to accommodate which encoding will be used. The simplest encoding, which is accurate by all audience and servers, is the raw encoding area pixel abstracts is beatific in left-to-right scanline order, and afterwards the aboriginal abounding awning has been transmitted, alone transfers rectangles that change. This encoding works actual able-bodied if alone a baby allocation of the awning changes from one anatomy to the abutting (like a abrasion arrow affective beyond a desktop, or argument actuality accounting at the cursor), but bandwidth demands get actual aerial if a lot of pixels change at the aforementioned time, such as back scrolling a window or examination full-screen video.

VNC by absence uses TCP anchorage 5900+N,56 area N is the affectation cardinal (usually :0 for a concrete display). Several implementations additionally alpha a basal HTTP server on anchorage 5800+N to accommodate a VNC eyewitness as a Java applet, acceptance accessible affiliation through any Java-enabled web browser. Different anchorage assignments can be acclimated as continued as both applicant and server are configured accordingly.

Using VNC over the Internet works able-bodied if the user has a broadband affiliation at both ends. However, it may crave avant-garde NAT, firewall and router agreement such as anchorage forwarding in adjustment for the affiliation to go through. Some users may accept to use burning clandestine networking applications such as Virtual Clandestine Arrangement (VPN) applications such as Hamachi to accomplish acceptance over the Internet abundant easier. Alternatively, a VNC affiliation can be accustomed as a LAN affiliation if VPN is activated as a proxy.

Note that the apparatus the VNC server is active on does not charge to accept a concrete display. Xvnc is the Unix VNC server, which is based on a accepted X server. To applications Xvnc is an X "server" (ie displays applicant windows), and to alien VNC users it is a VNC server. Applications can affectation themselves on Xvnc as if it were a accustomed X display, but they will arise on any affiliated VNC admirers rather than on a concrete screen.7 Alternatively a apparatus (which may be a workstation or a arrangement server) with screen, keyboard, and abrasion can be set up to cossack and run the VNC server as a account or daemon, again the screen, keyboard, and abrasion can be removed and the apparatus stored in an out-of-the way location.

In addition, the affectation that is served by VNC is not necessarily the aforementioned affectation apparent by a user on the server. On Unix/Linux computers that abutment assorted accompanying X11 sessions, VNC may be set to serve a accurate absolute X11 session, or to alpha one of its own. It is additionally accessible to run assorted VNC sessions from the aforementioned computer. On Microsoft Windows the VNC affair served is consistently the accepted user session.

VNC is frequently acclimated as a cross-platform alien desktop system. For example, Apple Alien Desktop for Mac OS X (and added recently, "Back to My Mac" in 'Leopard' - Mac OS X 10.5) interoperates with VNC and will affix to a Linux user's accepted desktop if it is served with x11vnc, or to a abstracted X11 affair if one is served with TightVNC. From Linux, TightVNC will affix to a Mac OS X affair served by Apple Alien Desktop if the VNC advantage is enabled, or to a VNC server active on Microsoft Windows.

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