protected void doErrorResponse(SipServletResponse response)
            throws ServletException, IOException {
        //The receiver of the message probably dropped off. Remove 
        //him from the list.
        String receiver = response.getTo().toString();
        removeUser(receiver);
    }
protected void doErrorResponse ( SipServletResponse response ) throws ServletException , IOException { String receiver = response . getTo ( ) . toString ( ) ; removeUser ( receiver ) ; }
This is called by the container when an error is received
regarding a sent message, including timeouts.