转换大写TCP模拟

package demo.network.tcp.other;

import java.io.*;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

//客户端
class TransClient implements Runnable {
    private Socket socket;

    TransClient(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in));
        try {
            //将从键盘录入的数据发给服务器
            PrintWriter out = new PrintWriter(socket.getOutputStream());//可用自动刷新
            String line = null;//储存发送的数据
            //读取服务器返回的大写数据
            BufferedReader bufIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            while ((line = bufr.readLine()) != null) {
                out.println(line);//发给服务器原数据，且必须加上换行，因为服务端是每次读一行（需要\n的结束标记）
                out.flush();//必须刷新，不刷新数据只存在PrintWriter中，并没有给服务端
                System.out.println(bufIn.readLine());//打印大写数据
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                bufr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

//服务器
class TransServer implements Runnable {
    private ServerSocket serverSocket;

    TransServer(ServerSocket serversocket) {
        this.serverSocket = serversocket;
    }

    @Override
    public void run() {
        Socket socket = null;
        try {
            //获取连接过来的客户端对象
            socket = serverSocket.accept();
            //将客户端对象的输入流转换为字符输入流并使用缓冲区修饰
            BufferedReader bufr = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            //反馈给客户端信息(将客户端发来数据转化为大写)
            OutputStream out = socket.getOutputStream();
            String line = null;
            while ((line = bufr.readLine()) != null) {
                System.out.println(socket.getInetAddress().getHostAddress() + ": " + line);//打印客户端发送的原数据
                out.write(line.toUpperCase().getBytes());//将客户端发来数据转化为大写，并发送回去
                out.write("\n".getBytes());//同理，客户端也是每次从服务端读取一行，需要有换行标记，否则一直阻塞
                out.flush();//刷新才能立刻发给客户端
                //简洁操作：可用true自动刷新和Print打印流的prinln
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (socket != null)
                    socket.close();
                serverSocket.close();//关闭服务器
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

class TextTrans {
    public static void main(String[] args) throws IOException {
        TransServer ts = new TransServer(new ServerSocket(8080));//务必优先开启服务端
        TransClient tc = new TransClient(new Socket(InetAddress.getLocalHost().getHostAddress(), 8080));

        new Thread(ts).start();
        new Thread(tc).start();
    }
}