Problem managing keepalive with sockets

Question

Hello friends, I am finding difficulty to manage keepalives in my socket-based client/server app. Please help.
I want to set a socket timeout so that the connection is closed by server after a set inactivity time. Theoretically, this is a cakewalk, because I can setSoTimeout on the socket. I set it to 30 min. This works fine in my local machine. But after I deploy the server on the remote machine (OS Linux Redhat), the soTimeout setting doesn't work. Client stops responding after about 5 minutes of inactivity. My problem is why this is happening and how can I solve this.
The code I am using is like this:
Socket  socket = ...;//obtain socket somehow
InputStream in = socket.getInputStream();
try{
  socket.setSoTimeout(30*60*1000);
  String fromClient = in.readLine();//blocking read
  //..do something with the message
catch(Exception e){
  System.out.println(e);
}When the connection goes dead (after about 5 min), no exception is caught at the above catch clause, why?
My guess is that a socket timeout of 5 min is set somewhere in the host machine, but if it is so, I have no idea where to check and how to reset. If the solution lies on the Linux side rather than on the Java side, ideally I would like to set a timeout value per socket (per app basis) so that my setting would not mess with other apps.
As an alternative, the client can be programmed (but have not tried yet) to send a dummy message every 2 or 3 min to keep the connection alive. But doing so would keep connection alive for ever, which I don't want.
What options are available to me?

Answer 1

the socket get disconnected once when there is no reply from the client ,so your time out won't work in case there is no reply from client , program such a way that a dummy conversation occurs between the client and server ,when there is no actual conversation ,then the timeout could work for you.