CM Login session duration in SDK

[jagadeesh]

Hi Friends,

I am using Cognos 8 SDK.

I am using the below line of code for CM Login, as part of my web-application.
cmService.logon(new XmlEncodedXML(getCredentialXMLString()), new   SearchPathSingleObject[] {});

the above line will get execute when the server load the web-application.

This will work fine and am able to fetch reports list, when i hit the page on next day, i got the exception as
CM-REQ-4159 Content Manager returned an error in the response header. This might be bcaz of expired CM login session, is my assumption.

When i restarted the web-app it started working fine.

how to know whether the CM Login session is alive or not. So that i can try to relogin again if it is expired?
Plz help me here.
Thanks in Advance.
-Jags