Universal Messaging Developer Guide : Web Client APIs : Web Developer's Guide for Adobe Flex : Creating a Session
Creating a Session
To interact with a Universal Messaging Server, the first thing to do is create a Universal Messaging Session object (see com.pcbsys.nirvana.client.nSession in the API documentation), which is effectively your logical and physical connection to a Universal Messaging Realm.
Creating a Universal Messaging Session Object
The Flex nSessionFactory create function takes four parameters:
*attributes : the nSessionAttributes for the Universal Messaging Realm Server (see com.pcbsys.nirvana.client.nSessionAttributes in the API documentation). To create an nSessionAttributes it requires a RNAME and a initialConnectionRetry count.
*username : The current user's username. This allows you to link sessions to already authenticated users, irrespective of what authentication technology you are using.
*appName : An arbitrary string which should ideally be unique to this application. Again, this is to help you monitor sessions using the Enterprise Manager GUI.
*errorCB : The callback if an error occurs.
The Flex code snippet below demonstrates the creation of an nSession and a nSessionAttributes object:

var RNAME : String = "nhp://nirvanahost:80";
var username : String = "myUserName";
var appName : String = "MyApplicationName";
var attributes : nSessionAttributes = new nSessionAttributes(RNAME,5);
var mySession : nSession =
nSessionFactory.create(attributes, username, appName, errorCB);
Initializing a Universal Messaging Session
Once the nSession object has been created, it must be initialized to create a connection to the server:

mySession.init(sessionInitCB);
Note that the nSession.init() call is asynchronous; it returns immediately, allowing Flex clients to continue processing due to their single thread.
To know when an nSession.init() call has completed, and also when server disconnects and reconnects, the init() method takes a callback function.
To enable the use of DataGroups and to create an nDataStream, you should pass an instance of nDataStreamListener to the init call.

public class SimpleStreamListener implements nDataStreamListener{
//implement onMessage callback for nDataStreamListener callbacks
}

var myListener:nDataStreamListener = new SimpleStreamListener();
mySession.init(sessionInitCB, myListener);
After initialising your Universal Messaging session, you will be connected to the Universal Messaging Realm. From that point, all functionality is subject to a Realm ACL check. If you call a method that requires a permission your credential does not have, you will receive an nSecurityException.
Creating a Multiplex Session
It is also possible to create a Multiplex Session. This involves creating a session from an existing session, either via the appropriate nSession object or its associated nSessionAttributes. These two sessions will now appear to act as normal sessions, but will, in fact, share a single connection. Below is an example of how to create multiplex sessions, both via nSession and via nSessionAttributes:

// original session
private var _session:nSession;

// original session attributes
private var attributes:nSessionAttributes;

// construct a new session with the nSession object
nSessionFactory.createMultiplexed(_session, nSessionCB, errorCB);

// construct a new session with the nSessionAttributes object
nSessionFactory.createMultiplexedWithAttributes(attributes, nSessionAttributesCB,
"flex", "session3", errorCB);

//...

private function nSessionCB(e:*):void {
_session2 = e;
_session2.init(sessionInitCB, this, true);
}

private function nSessionAttributesCB(e:*):void {
_session3 = e;
_session3.init(sessionInitCB, this, true);
}
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