客户端断开连接时服务器挂起

Question

i am creating a multiple-client/server app whenever any client disconnects from my server it just hangs. how can i set any condition that will tell me print some message whenever any client disconnects from the server here is my server code

class ServerThread implements Runnable {

    public void run() {
        Socket socket = null;
        try {
            System.out.println("server starting.......");
            serverSocket = new ServerSocket(SERVERPORT);
        } catch (IOException e) {
            e.printStackTrace();
        }
        while (!Thread.currentThread().isInterrupted()) {

            try {
                System.out.println("Ready to accept.......");
                socket = serverSocket.accept();

                System.out.println(" client Connected with ip address =" +socket.getRemoteSocketAddress().toString());

                CommunicationThread commThread = new CommunicationThread(socket);
                new Thread(commThread).start();

            } catch (IOException e) {
                e.printStackTrace();
                System.out.println("catch block");

            }

        }
    }
}

class CommunicationThread implements Runnable {

    private Socket clientSocket;

    private BufferedReader input;

    public CommunicationThread(Socket clientSocket) {

        this.clientSocket = clientSocket;

        try {

            this.input = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void run() {


        while (!Thread.currentThread().isInterrupted()) {

            try {

                String read = input.readLine();

                updateConversationHandler.post(new updateUIThread(read));

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

any help will be appreciated

Answer 1

It's not clear whether you mean disconnect because the conversation was over (ie: everything completed successfully) or the disconnect is because of some network problems (or the client canceled the request).

If it's the first case, then it's easy: the protocol you are using (your own, or http, or whatever) is in charge of defining how to determine that a conversation was over. If that situation arises, then you just close the socket.

If it's the second case, then you'd have to have an algorithm in place to determine whether or not the connection must be closed. For instance, by implementing a timeout, or a slow-read threshold. Take a look at the Socket's javadoc for instructions on how to set a timeout.

It's also worth noting that it's fine to create your own servers when you want to practice or learn something, but you'd be better off using an existing solution, like vert.x or a slimmed down version of Wildfly, for instance. The overhead of such servers is very low, nowadays, while still providing very robust networking capabilities.