Multiple log-in problem
<p>We have a web application with feature for logging in with  credientials 
The important requirement is once the user logs in he is not allowed to login from any other system or even another browser on same system 
 We used following solution which is mssql based : We have kept " Is_Loggedin" as a column with data type "bit" in a table. when a user logs in we set the flag  as "1" sowhen someone tries to log again ,the system is showing the error "The user is already logged in"
 When user logsout bit turns to "0"indicating user logged out. 
However this logic is failing in following scenarios</p>

<p>Problem scenario:
When user closes the browser the flag is "1"and user is locked in or situations when user gets system problem and unable to log out </p>

<p>Is there a better logic to handle this requirement?</p>
