Java套接字读取超时异常

Question

I try to overcome a user disconnection detection on the server side using read timeout. This is part of my code:

try {
        socket.setSoTimeout(3000);
        in = new DataInputStream(socket.getInputStream());
        out = new DataOutputStream(socket.getOutputStream());
        usr = new User(in.readUTF());
        usr.connectUser();
        int i=0;
        while(true){
            try{
                i = in.readInt();
            }
            catch(SocketTimeoutException e){
                System.Out.Println("Timeout");
                // user connected, no data received
            }
            catch(EOFException e){
                System.Out.Println("Disconnected");
                // user disconnected
            }
        }
    }
    catch(Exception  e){
        // other exceptions
    }

the code works fine except the "user disconnected" issue. i want to catch the timeout exception and just continue waiting for data but only if the client still connected. why i never get other exception than SocketTimeoutException? shouldn't i get IOException while in.readInt() can't use the socket because client disconnected?

is there any other simple way to detect user disconnection? i mean as unwanted disconnection, like user had suddenly wifi shutdown etc...

thanks, Lioz.

Answer 1

If the client didn't write anything within the timeout period, you get a SocketTimeoutException. If he disconnected instead of writing anything, you get an EOFException. Catch them separately. If you didn't get an EOFException, he didn't disconnect.