P2P connection not closing when refreshing the browser

I have developed P2P video conference application. It is working fine when using chrome and firefox. But the problem is in IE.

Problem:

User1 refreshes the browser while in conference. The SWF gets load and starts to publish again. But the other users are able to hear the voice of the user1 even when he is refreshing. The issue is the P2P connection is not closing while refreshing in IE.

I need to close the connection. Am using FMS 4.5 and AS3. We cannot ping the user from serverside as it is a P2P connection. Is there any way to find out if the user is still connected or not. Please suggest me how to close the connection.