w3ntp has asked for the wisdom of the Perl Monks concerning the following question:
I have a TCP Client Application on the other side of a firewall that communicates with a local TCP Server Application. The Firewall is setup to block all traffic except this TCP traffic over its specific port. I have found that if the TCP connection on the other side of the firewall is abruptly terminated (yanked cable), the local TCP connection remains in the ESTABLISHED state forever. So what I am trying to do is find out if the remote client is up; possibly by sending a dummy TCP ack or some connection scheme to a client. Unfortunately, the local netstat and lsof commands do not detect the dropped TCP session.
Any ideas or thoughts?