Why it shows unique usernames irrespective of their usernames.

What do you mean ?

After login ,it shows some "guest-10a" like this in online users list but i wanna names in the list ?how can i achieve it?

You will have to set $ses variable to current userid in your copy pasted code

Before it shows online users and chatroom module,

I set the session variable like this

if($_SESSION)
{
$ses=$id;
}
else{
$ses=null;
}

After this, it does not show anything. chat room and online users list disappeared..