If the connection is closed, why the no other exceptions are detected to notify the application.Because this is the exception to notify the application. TCP doesn't provide anything else, unless the firewall sends a FIN in both directions, which I doubt it would do. So nothing will happen at all until an RST is provoked by I/O at either peer.
14845 2012-02-07 22:37:46 10.* 10.* DNP 3. len=1,from 52156 to 29466,ACKIt seems to be retransmitting an ACK for some reason. I think at this point you should take it to news:comp.protocols.tcp-ip, with the complete tcpdump.
14848 2012-02-07 22:37:46 10.* 10.* DNP 3. [TCP Restransmission] len=1,from from 52156 to 29466,ACK