java socket 关闭的方法

public class BIOServer {

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(4396);
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("socket = " + socket);
            new Thread(() -> {
                try {
                    InputStream in = socket.getInputStream();
                    OutputStream out = socket.getOutputStream();
                    out.write("hello! I get your message that is follow".getBytes(Charset.forName("UTF-8")));
                    byte[] buf = new byte[1024];
                    int len;
                    while ((len = in.read(buf)) != -1) {
                        System.out.print(new String(buf, 0, len, Charset.forName("UTF-8")));
                        out.write(buf, 0, len);
                    }
                    out.write("n end n".getBytes(Charset.forName("UTF-8")));
                    out.flush();
                    socket.shutdownInput();
                    System.out.println("server close is");
                    Thread.sleep(5000);
                    System.out.println("server close os");
                    socket.shutdownOutput();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    try {
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }).start();
        }
    }

}

public class BIOClient {

    public static void main(String[] args) throws IOException, InterruptedException {
        Socket socket = new Socket("127.0.0.1", 4396);
        InputStream in = socket.getInputStream();
        new Thread(() -> {
            BufferedInputStream bufferIn = new BufferedInputStream(in);
            byte[] buf = new byte[1024];
            try {
                int len;
                while ((len = bufferIn.read(buf)) != -1) {
                    System.out.print(new String(buf, 0, len, Charset.forName("UTF-8")));
                }
            }catch (Exception e) {
                e.printStackTrace();
            }
            try {
                socket.shutdownInput();
                System.out.println("client close is");
//                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }).start();
        OutputStream out = socket.getOutputStream();
        int cout = 10;
        while (cout-- > 0) {
            out.write(("this time is " + System.currentTimeMillis() + "n").getBytes("UTF-8"));
        }

        Thread.sleep(5000);
        System.out.println("client close os");
        socket.shutdownOutput();
    }
}

实验发现connection经历以下状态

经过试验发现java socket 中的
close 原理为主动发起一方 发送 FIN
被动方会自动发送ACK，但只有自己调用了close才会发送FIN
然后对面会自动发送ACK
成功关闭 TCP连接

对shutdowninput 和 output
只有shutdownoutput时候主动方才会发送FIN，对端自动发送ACK。只有对端自己调用shutdownoutput时才会发送FIN，此时的原主动方会自动发送ACK。
成功关闭TCP连接。

shutdowninput 只有关闭缓冲区的作用