AIX network parameters to close TCP sockets of unplugged devices

We have an AIX box, running what we call in banking "ATM Switch" not the ATM networking switch, but the bank ATM driver. where we have some ATM machines connected to two server processes.

The problem is, when we disconnect any of these machines, the netstat -na| grep <port number> command shows that the socket established for this disconnected device is still established, we have to manually send a command from the software to make the socket aware that it is not live anymore.

Is there a parameter on tcp level to make this connection aware within a minute or two that this device is not connected anymore?
we had the following parameters set with root privileges:

• no -o tcp_keepidle=1000
• no -o tcp_keepcnt=2
• no -o tcp_keepintvl=150
• no -o tcp_finwait2=100

it was originally having the default values. but even after we changed these parameters and restarted the server processes, the problem was still there.