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# The VNC Protocol

VNC (Virtual Network Computing) software makes it possible to view and interact with one computer (the "server") from any other computer or mobile device (the "viewer") anywhere on a network.

To run a Qtopia Core application using the VNC protocol, Qtopia Core must be configured using the `-qt-gfx-vnc` option:

    cd path/to/Qtopia/Core
    ./configure -qt-gfx-vnc
    make

Then start a Qtopia Core master application (i.e. construct a QApplication object with the QApplication::GuiServer flag or use the -qws command line parameter. See the Running Applications documentation for details). In addition, use the `-display` option to specify the VNC server's driver. For example:

    cd path/to/Qtopia/Core/examples/widgets/analogclock
    ./analogclock -qws -display VNC:0

To interact with the application over the network, run a VNC client pointing at the machine that is running the Qtopia Core master application. VNC clients are available for a vast array of display systems: X11, Windows, Amiga, DOS, VMS, and dozens of others. For example, using the X11 VNC client to view the application from the same machine:

    vncviewer localhost:0

Qtopia Core will create a 640 by 480 pixel display by default. Alternatively, the QWS_SIZE environment variable can be used to set another size, e.g. `QWS_SIZE=240x320`.

The Virtual Framebuffer The Virtual Framebuffer is an alternative technique recommended for development and debugging purposes. The virtual framebuffer emulates a framebuffer using a shared memory region and the `qvfb` tool to display the framebuffer in a window. Its use of shared memory makes the virtual framebuffer much faster and smoother than using the VNC protocol, but it does not operate over a network. |

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