Listener Class

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

Table 13-23 Summary of Listener Methods

Method	Summary
Listener()	`Listener` class constructor.
getAgentList()	Retrieves the list of `Agent`s for which the `Listener` provides its services.
getTimeOutForListen()	Retrieves 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()

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

Syntax

vector<Agent> getAgentList() const;

getTimeOutForListen()

Retrieves 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, complete the following steps:

Registers each Agent listener through a setAgentList() call.
Make a blocking call to setTimeOutForListen() that will return 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>& agList);

Parameter	Description
agList	The list of `Agent`s.

setTimeOutForListen()

Specifies the time out for a listen() call.

Syntax

void setTimeOutForListen(
   int waitTime);

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