Listener Class

The Listener class encapsulates the ability to listen for Messages, on behalf of registered Agents, at specified queues.

Table 10-20 Summary of Listener Methods

Method	Summary
Listener()	`Listener` class constructor.
getAgentList()	Retrieve the list of `Agent`s for which the `Listener` provides its services.
getTimeOutForListen()	Retrieve the time out for a call.
listen()	Listens for `Message`s and returns the name of the `Agent` for whom a `Message` is intended.
setAgentList()	Specifies the list of `Agent`s for which the `Listener` provides its services.
setTimeOutForListen()	Specifies the time out for a listen() call.

Listener()

Listener class constructor.

Syntax	Description
Listener( const Connection* conn);	Creates a `Listener` object.
Listener( const Connection* conn vector<Agent> &aglist, int waitTime=0);	Creates a `Listener` object and sets the list of `Agent`s on behalf of which it listens on queues. Also sets the waiting time; default: no waiting.

Parameter	Description
conn	The connection of the new `Listener` object.
aglist	The list of agents on behalf of which the `Listener` object waits on queues; clients of this `Listener`.
waitTime	The time to wait on queues for messages of interest for the clients; in seconds.

getAgentList()

Retrieve the list of Agents for which the Listener provides its services.

Syntax

vector<Agent> getAgentList() const;

getTimeOutForListen()

Retrieve the time out for a call.

Syntax

int getTimeOutForListen() const;

listen()

Listens for Messages on behalf of specified Agents for the amount of time specified by a previous setTimeOutForListen() call. Returns the Agent for which there is a Message.

Syntax

Agent listen();

Note:

This is a blocking call. Prior to this call, the following steps should be completed:

Each Agent must be registered with the listener using setAgentList() method.
The time out parameter should be set using the setTimeOutForListen() method. This is a blocking call that returns when a Message for one of the Agents on the list arrives. If no Messages arrive before the wait time expires, the call returns an error.

setAgentList()

Specifies the list of Agents for which the Listener provides its services.

Syntax

void setAgentList(
   vector<Agent>& list);

Parameter	Description
list	The list of `Agent`s.

setTimeOutForListen()

Specifies the time out for a listen() call.

Syntax

void setTimeOutForListen(
   int timeOut);

Parameter	Description
timeOut	The time interval, in seconds, during which the `Listener` is waiting for `Message`s at specified queues.