底部附上了效果圖
伺服器程式碼：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(2000);
        System.out.println("伺服器準備就緒");
        //System.out.println("client: "+ socket.getLocalAddress() + " p : " + socket.getLocalPort());
        System.out.println("伺服器資訊 ： " + serverSocket.getInetAddress() + " p : " + serverSocket.getLocalPort());

        //等待客戶端連線
        while (true) {
            Socket client = serverSocket.accept();
            ClientHandler clientHandler = new ClientHandler(client);
            clientHandler.start();
        }
    }
    private static class ClientHandler extends Thread{
        private Socket socket;
        ClientHandler(Socket socket){
            this.socket = socket;
        }
        private boolean flag = true;

        @Override
        public void run() {
            //super.run();
            System.out.println("新客戶端連線： " + socket.getInetAddress() + "p: " + socket.getPort());

            try {
                //得到列印流，用於資料輸出；伺服器回送資料使用
                PrintStream soketOutput = new PrintStream(socket.getOutputStream());
                //得到輸入流，用於接收資料
                BufferedReader socketInput = new BufferedReader(
                        new InputStreamReader(socket.getInputStream()));
                do {
                    //客戶端拿到一條資料
                    String str = socketInput.readLine();

                    //String echo = socketInput.readLine();
                    if ("bye".equalsIgnoreCase(str)) {
                        flag = false;
                        soketOutput.println("bye");
                    }else {
                        //列印到螢幕，並回送資料長度
                        System.out.println(str);
                        soketOutput.println("回送： " + str.length());
                    }
                }while (flag);
                socketInput.close();
                soketOutput.close();

            } catch (IOException e) {
                System.out.println("連線異常斷開");
            }finally {
                //連線關閉
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("客戶端已退出： " + socket.getInetAddress() + " p : " + socket.getPort());
        }
    }
}


客戶端程式碼：
import java.io.*;
import java.net.Inet4Address;
import java.net.InetSocketAddress;
import java.net.Socket;

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket();
        socket.setSoTimeout(3000);
        //連線本地，埠2000；超時時間為3000ms
        socket.connect(new InetSocketAddress(Inet4Address.getLocalHost(),2000), 3000);
        System.out.println("伺服器已連線");
        System.out.println("client: "+ socket.getLocalAddress() + " p : " + socket.getLocalPort());
        System.out.println("伺服器資訊 ： " + socket.getInetAddress() + " p : " + socket.getPort());
        try {
            todo(socket);
        }catch (Exception e){
            System.out.println("關閉異常");
        }
        socket.close();
        System.out.println("客戶端已退出");
        
    }
    private static void todo(Socket client) throws IOException{
        InputStream in = System.in;
        BufferedReader input = new BufferedReader(new InputStreamReader(in));
        //得到soket輸出流，並轉換為列印流
        OutputStream outputStream = client.getOutputStream();
        PrintStream sockePrintStream = new PrintStream(outputStream);
        // 得到sokcet輸入流，並轉換為socketBufferReader
        InputStream inputStream = client.getInputStream();
        BufferedReader sokcetBufferedReader = new BufferedReader(new InputStreamReader(inputStream));

        boolean flag = true;
        do {
            //鍵盤讀取一行
            String str = input.readLine();
            //傳送到伺服器
            sockePrintStream.println(str);

            //從伺服器讀取一行
            String echo = sokcetBufferedReader.readLine();
            if ("bye".equalsIgnoreCase(echo)) {
                flag = false;
            }else {
                System.out.println(echo);
            }
        }while (flag);
        //關閉socket流
        sockePrintStream.close();
        sokcetBufferedReader.close();
    }
}