Restricting Access to the System

A port monitor must be able to restrict access to the system without disturbing services that are still running. In order to do this, a port monitor must maintain two internal states: enabled and disabled. The port monitor starts in the state indicated by the ISTATE environment variable provided by the sac. See "The SAC/Port Monitor Interface".

Enabling or disabling a port monitor affects all ports for which the port monitor is responsible. If a port monitor is responsible for a single port, only that port will be affected. If a port monitor is responsible for multiple ports, the entire collection of ports will be affected.

Enabling or disabling a port monitor is a dynamic operation: It causes the port monitor to change its internal state. The effect does not persist across new invocations of the port monitor.

Enabling or disabling an individual port, however, is a static operation: It causes a change to an administrative file. The effect of this change will persist across new invocations of the port monitor.