The RFB protocol is used to transmit screen pixel data from one computer to another over a network, and send control events in return. It’s a simple yet powerful protocol invented by RealVNC.
RealVNC Server captures the desktop of the computer in real-time and sends it to RealVNC Viewer for display. RealVNC Viewer gathers your input (mouse, keyboard, or touch) and sends it for RealVNC Server to inject and actually achieve remote control.
You need a RealVNC Server for the remote computer you want to control, and a RealVNC Viewer for the computer or mobile device you want to control from. You can install and license these applications in advance, or download and run them on-demand, in the way that suits you best. Or do both, in different circumstances.
RealVNC Connect uses the latest commercial version of the RFB protocol, originally defined as RFC 6143.
The current commercial version (6.0) of the RFB protocol as used in RealVNC Connect adds a significant number of security, performance and functionality improvements over the protocol described in RFC6143.
For a technical explanation of the security of the RFB protocol used in RealVNC Connect, see the VNC Connect Security Whitepaper.