subscribe

Name

subscribe — start subscribing to one or more subjects or list the current subscriptions

Synopsis

Supported for RTserver:

subscribe 
subscribe project subject 

Supported for RTclient and RTmon:

subscribe 
subscribe [ -load_balancing_off ] subject1 subject2 ... 

Description

The subscribe command adds the specified subjects to the list of subjects to which the RT process is already subscribing. If no subjects are specified, the RT process displays the names of the subjects it is currently subscribed to. The subscribe command is additive. Each time you subscribe to a subject, it is added to the list of subjects to which the RT process is currently subscribed.

An RTserver subscribe is normally used with a wildcard subject name that matches a large number of RTclient subscribes. This reduces the amount of inter-RTserver dynamic message routing information exchanged. For RTserver, the subscribe command can be used interactively, but is most commonly used from a rtserver.cm startup command file.

For RTclient and RTmon, the subscribe command takes a variable number of subjects. By default, subscribing to a subject allows RTclient or RTmon to be a load-balanced receiver if a message is published to the subject with load balancing. This can be overridden if the -load_balancing_off modifier is specified, which allows RTclient or RTmon to always receive the subject in addition to one of the load-balanced subscribers. For more information on load balancing, see Chapter 3, Publish-Subscribe.

An RTclient process must call the API function TipcInitCommands to enable access to the subscribe command.

Caution

To prevent irreversible damage to your SmartSockets system, this command should not be specified with the Enable_Control_Msgs option without careful supervision.

For RTserver, the subscribe command should only be used for projects where you have limited bandwidth (for example, over a 56.6K modem) or on large-scale projects where there are many matching subjects that can be covered by a wildcard subject subscribe in RTserver.

If RTclient or RTmon is not connected to RTserver, it does so before subscribing.

The subscribe command acts on the global connection unless received via a CONTROL message, in which case the command is applied to the connection on which it was received.

See Also

unsubscribe

Examples

Here is an example of subscribing to subjects for RTclients:

PROMPT> subscribe _time 
Start subscribing to subject /_time.