Threads and Socket client.

[semperfy]

Hi guys, I've been programming in java for some time, but I'm not very advanced, I have to make a socket application, client side only.
This application receives data, searches the database, and returns a value to the server, is working, there is no delay in response, all ok, but the problem is that I can not know when the connection to the server was broken, and the server sends the right question, doesn't answer any kind of command, so I can't make a keepAlive, so I decided to create a timer to restart all clients in 5 minutes, but I noticed that some clients don't stop in time, starting 2 clients on the same server, and with that I get a block on the server, would anyone have any other idea to perform this process?
For you to understand, my scenario is as follows:
8 turnstiles running as a server (no option to run as a client)
1 server, running my application, starting 8 clients, running in threads
This is the code where I start clients, which get ips from the database turnstiles, using the same port

Thank you...