![]() ![]() Īlthough possible even on low bandwidth, using VNC over the Internet is facilitated if the user has a broadband connection at both ends. A HTML5 VNC client implementation for modern browsers (no plugins required) exists too. Different port assignments can be used as long as both client and server are configured accordingly. Several implementations also start a basic HTTP server on port 5800+ N to provide a VNC viewer as a Java applet, allowing easy connection through any Java-enabled web-browser. VNC by default uses TCP port 5900+ N, where N is the display number (usually :0 for a physical display). This encoding works very well if only a small portion of the screen changes from one frame to the next (as when a mouse pointer moves across a desktop, or when text is written at the cursor), 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). The simplest encoding, supported by all clients and servers, is raw encoding, which sends pixel data in left-to-right scanline order, and after the original full screen has been transmitted, transfers only rectangles that change. The VNC protocol allows the client and server to negotiate which encoding they will use. For example, there are various encodings (methods to determine the most efficient way to transfer these rectangles). ![]() In its simplest form, the VNC protocol can use a lot of bandwidth, so various methods have been devised to reduce the communication overhead. The server sends small rectangles of the framebuffer to the client. One advantage of listening mode is that the server site does not have to configure its firewall to allow access on port 5900 (or 5800) the duty is on the viewer, which is useful if the server site has no computer expertise and the viewer user is more knowledgeable. And a server can connect to a viewer in "listening mode" on port 5500. Alternatively (depending on the implementation) a browser can connect to the server (default port: 5800). In the normal method of operation a viewer connects to a port on the server (default port: 5900).
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