The Broker's Methods

Conventions

<class>

Identifying a class of objects. For instance, in the call

Connections list

Connections is the class of all connections to the browser. The call will return a list of the names of all the connections.

<class>.<instanceId>

Identifying an object (instance of a class). For instance, in the call

StartableServers.Recognizer start

StartableServers.Recognizer identifies a StartableServer by the name Recognizer. The call will cause the server to be started.

<class>.<instanceId>.<attribute>

Identifies an attribute of the object. For instance, in the call

StartableServers.Recognizer.commandLine get

commandLine is an attribute of the StartableServer Recognizer. The call will return the commandLine for the Recognizer.

If the value of an attribute of the object is an object itself, one might have identifiers like:

StartableServers.Recognizer.connection.state get

Where connection is an attribute of the recognizer StartableServer, and state is an attribute of the connection.

Subscriptions

These functions work as follows. <publication> is the name of an object which one can subscribe to. 

<publication> subscribe <moduleName> <moduleData>

<subscriptionId>

Subscribes to the publication. moduleName is the name of the module which will be informed of changes to the object. moduleData is value supplied by the subscriber to identify the subscription. It will be included in the notification calls.

The result is an identifier used to refer to this subscription in future calls.

When the object changes, moduleName receives a call of the form:

Subscription.<moduleData> notify <notification message>

If for some reason the module with the publication wishes to cancel the subscription, it will make a call like:

Subscription.<moduleData> cancel

<publication> cancelSubscription <subscriptionId>

none

Cancels the subscription.
 

The following calls can be made to the Broker:

Connection list
Connection.<name> subscribe <clientName>
Connection.<name>.log get
Connection.<name>.log subscribe

Subscription.<id> cancel
Subscription.<id> notify
 

Our implementation of the Broker is written in Java, and should therefore run on any platform which has a Java 1.1 environment. Sun Microsystems' implementation of Java (called the Java Runtime Environment) is freely available from JavaSoft. If you wish to develop in Java, you should get the Java Development Kit (JDK) instead.

The Broker itself is a stand-alone Java program, with class SE.kth.speech.broker.Broker. It takes two parameters: the port on which it listens for incoming TCP connections, and the password used to access some restricted features (such as changing the set of startable servers.)

To use the Broker, first you must download the Java classes. Then the supplied .jar (Java Archive) files must be added to the CLASSPATH (Under UNIX, CLASSPATH is an environment variable). Under tcsh, this is done with a command like (but you will hopefully want to put the files in a better place than /tmp):

setenv CLASSPATH /tmp/broker.jar:/tmp/broker/erl.jar

java SE.kth.speech.broker.Broker 4711 guess

And bring up the Broker User Interface with (you might want to replace localhost with the host name you are running the broker on):

java SE.kth.speech.broker.GUI localhost 4711

© Copyright 1997 Erland Lewin and the members of the Center for Speech Technology