How do we know if someone is online—I mean, really, really know?

[chinmay.sahoo]

While we would like users to tell us when they sign off, we can’t know for sure. A user’s connection might have died, for example. To make sure that we know when a user has signed off, we might try regularly pinging the client to make sure it’s still there.

 

[jacks009]

I agree with this post.