Java：套接字关闭连接和ObjectInputStream

Question

My code looks like this, this is Server code ( Runnable )

public void run() {
    while (true) {
        try {
            System.out.println("Waiting for client...");
            this.socket = serverSocket.accept();
            System.out.println("Client accepted");
            while (true) {
                readCommand();
                try {
                    Thread.sleep(2);
                } catch (Exception e) {
                }
            }
        } catch (Exception ex) {
            Main.error("Server stopped for current host", ex);
        }
    }
}

My problem is: when the client closes the connection, he still waiting to read the command in readCommand(); until a command was sent and an EOFException will be thrown. This is my readCommand method:

private void readCommand() throws Exception {
    Object o = new ObjectInputStream(socket.getInputStream()).readObject();
    if (o instanceof Command) {
        ((Command) o).execute();
        return;
    }
    if (o instanceof Recorder) {
        System.out.println("Recording received");
        ((Recorder) o).executeRecord();
        return;
    }
    if (o instanceof MyKeyEvent) {
        ((MyKeyEvent) o).execute();
        return;
    }
}

So I think before reading it has to check if the connection is open.

Edit: If I evaluate the run -method code, the EOFException is thrown in the try-catch-body . But he stops accepting clients.

Answer 1

An EOFException is exactly what I'd expect if the client closes the connection. So I'm not quite sure what your problem actually is . Perhaps you need to distinguish between an expected client disconnect and an unexpected client disconnect. In which case you should perhaps send some sort of End-of-message object to mark the end of transmission ?

If you want to check if info is available, there's an available() method on the stream. I don't think you need your Thread.sleep(2) , btw, since I would expect a read on a valid input stream to hang in the absence of data.

Answer 2

You can also "just" add another try-catch to catch just the EOFException

public void run() {
    while (true) {
        try {
            System.out.println("Waiting for client...");
            this.socket = serverSocket.accept();
            System.out.println("Client accepted");
            try {
                while (true) {
                    readCommand();
                    try {
                        Thread.sleep(2);
                    } catch (Exception e) {
                    }
                }
            } catch (EOFException ex) {
                System.out.println("client closed");
            }
        } catch (Exception ex) {
            Main.error("Server stopped for current host", ex);
        }
    }
}

sure, the End-of-command is much smarter/elegant...
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