Screen Sharing is implemented by using standard VNC protocol over an MSRP connection. The minimum bandwidth required for a reasonable experience us 1 Mbit/s. Make sure that all debugging is disabled during Screen Sharing as it can overload the CPU.
The party sharing the Screen must have enabled Screen Sharing in System Preferences and set the option Anyone may request permission to control screen in Computer Settings section of the Share Screen panel.
Screen Sharing Party
First Blink alerts the user about an incoming request for Screen Sharing. If accepted, MacOSX VNC server will asks to confirm the Screen Sharing request. The request originates from the localhost (127.0.0.1) as the connection runs through Blink.