nserve automatically transmits a message to all tasks that have a queue whenever another task registered with nserve starts or stops. This mechanism makes it very simple for user tasks to respond to changes in the system. For example, a user task may want to know when a DataHub for a particular domain has started in order to register for exceptions from some or all of its points. These messages will be transmitted to the user task with a message type of IP_ASYNC and a command of IP_SUB_LISP. When a task starts or stops, nserve will send a message to all other registered tasks on the network as: (taskstarted name queue domain node pid), or (taskdied name queue domain node pid).