（三）阻塞式编程BIO

public class Server {
    public static void main(String[] args) {

        final String QUIT = "quit";
        final int DEFAULT_PORT = 8888; // 服务器端使用8888作为监听端口
        ServerSocket serverSocket = null;

        // 1.绑定监听端口
        try {
            serverSocket = new ServerSocket(DEFAULT_PORT); // 创建ServerSocket实例
            System.out.println("启动服务器，监听端口" + DEFAULT_PORT);

            while (true) {
                // 2.等待客户端连接，accept()函数是阻塞式的
                Socket socket = serverSocket.accept();
                System.out.println("客户端[" + socket.getPort() + "]已连接");

                // 3.获取IO流
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(socket.getInputStream())  // InputStreamReader：将InputStream转换为Reader
                );
                BufferedWriter writer = new BufferedWriter(
                        new OutputStreamWriter(socket.getOutputStream())
                );

                // 4.读取客户端发送的消息
                String msg = null;
                while ((msg = reader.readLine()) != null) {  // readLine()返回分隔符前的所有信息
                    System.out.println("客户端[" + socket.getPort() + "]" + msg);
                    // 5.回复客户发送的消息
                    writer.write("服务器：" + msg + "\n");
                    writer.flush(); // 防止有遗留的消息留在缓冲区

                    // 查看客户端是否退出
                    if (QUIT.equals(msg)) {
                        System.out.println("客户端[" + socket.getPort() + "]已断开连接" );
                        break;
                    }
                }

            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 6.不管是否有异常，都可安全的关闭资源
            if (serverSocket != null) {
                try {
                    serverSocket.close();
                    System.out.println("关闭serverSocket");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

public class Client {
    public static void main(String[] args) {
        final String QUIT = "quit";
        final String DEFAULT_SERVER_HOST = "127.0.0.1";
        final int DEFAULT_SERVER_PORT = 8888;
        Socket socket = null;
        BufferedWriter writer = null;

        // 1.创建Socket
        try {
            socket = new Socket(DEFAULT_SERVER_HOST, DEFAULT_SERVER_PORT);

            // 2. 创建IO流
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(socket.getInputStream())
            );
            writer = new BufferedWriter(
                    new OutputStreamWriter(socket.getOutputStream())
            );

            // 3.等待用户输入信息
            BufferedReader consoleReader = new BufferedReader(
                    new InputStreamReader(System.in) // System.in：标准的输入流，默认从键盘输入
            );
            while (true) {
                String input = consoleReader.readLine();

                // 4.发送消息给服务器
                writer.write(input + "\n"); // 加上分隔符，为了保证readLine()触发
                writer.flush();

                // 5.读取服务器返回的消息
                String msg = reader.readLine();
                System.out.println(msg);

                // 查看用户是否退出
                if (QUIT.equals(input)) {
                    break;
                }
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 关闭外层流的同时，内层流也会自动关闭，因此如果关闭writer，那么socket也会被关闭
            if (writer != null) {
                try {
                    writer.close();
                    System.out.println("关闭socket");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}