dpy
Specifies the display screen on which the X Server is to accept requests from X clients. If the display option is not specified, X uses the display screen specified by your DISPLAY environment variable. The display option has the format hostname:number. Using two colons (::) instead of one (:) indicates that DECnet is to be used for transport.
port
Specifies the port for which PortNotify events are to be generated when its attributes are changed using XvSetPortAttribute(3X).
onoff
Specifies whether notification is to be enabled or disabled.