How does the server know when a client disconnects from the server socket?
If a client closes its connection to the server correctly by using java.net.Socket.close(), then any subsequent sending of data over the input stream will result in a java.io.IOException on the server side. However, should the client not close down correctly because of network, hardware or OS failure, then the client socket is still open, and from the server perspective the client can still receive information. A good way to handle this scenario is to set a timeout limit on the socket connection, and poll the client with test messages. If the client does not acknowledge these messages within the timeout period, then the server can assume that the client is down, and then disconnect. Your client will need to be programmed to automatically return acknowledgments for all data transfers from the server. Here you will find what the server should include.
