int XGrabServer(Display *display);
int XUngrabServer(Display *display);
Specifies the connection to the X server.
The XGrabServer function disables processing of requests and close downs on all other connections than the one this request arrived on. You should not grab the X server any more than is absolutely necessary.
The XUngrabServer function restarts processing of requests and close downs on other connections. You should avoid grabbing the X server as much as possible.
XGrabButton(3), XGrabKey(3), XGrabKeyboard(3), XGrabPointer(3)
Xlib - C Language X Interface
The man page XUngrabServer(3) is an alias of XGrabServer(3).