use jester with SSE (server side event) example

[mrhdias]

So far, so good. But imagine this situation. What happens if the client closes 
the browser and the connection to the server while the process is working on a 
big query it just received from the client? In this case, nobody will ever take 
a look at the query results, so it makes a lot of sense to stop the process 
right away and clean the resources, as soon as the client closes the browser 
and the connection goes out. The problem is: How can we tell if a connection 
has been closed by the client? I thought the isclosed function from asyncnet 
lib did that! But it doesn't.