Client

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();
        // 超時時間
        socket.setSoTimeout(3000);

        // 連線本地，埠2000；超時時間3000ms
 

        socket.connect(new InetSocketAddress(Inet4Address.getLocalHost(), 2000), 3000);

        System.out.println("已發起伺服器連線，並進入後續流程～");
        System.out.println("客戶端資訊：" + socket.getLocalAddress() + " P:" + socket.getLocalPort());
        System.out.println("伺服器資訊：" + socket.getInetAddress() + " P:" +
 
 socket.getPort());

        try {
            // 傳送接收資料
            todo(socket);
        } catch (Exception e) {
            System.out.println("異常關閉");
        }

        // 釋放資源
        socket.close();
        System.out.println("客戶端已退出～");

    }

    private static void todo(Socket client) throws IOException {
 

        // 構建鍵盤輸入流
        InputStream in = System.in;
        BufferedReader input = new BufferedReader(new InputStreamReader(in));


        // 得到Socket輸出流，並轉換為列印流
        OutputStream outputStream = client.getOutputStream();
        PrintStream socketPrintStream = new PrintStream(outputStream);


        // 得到Socket輸入流，並轉換為BufferedReader
        InputStream inputStream = client.getInputStream();
        BufferedReader socketBufferedReader = 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
            socketPrintStream.println(str);


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

        // 資源釋放
        socketPrintStream.close();
        socketBufferedReader.close();

    }


}

Server

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 server = new ServerSocket(2000);


        System.out.println("伺服器準備就緒～");
        System.out.println("伺服器資訊：" + server.getInetAddress() + " P:" + server.getLocalPort());


        // 等待客戶端連線
        for (; ; ) {
            // 得到客戶端
            Socket client = server.accept();
            // 客戶端構建非同步執行緒
            ClientHandler clientHandler = new ClientHandler(client);
            // 啟動執行緒
            clientHandler.start();
        }

    }

    /**
     * 客戶端訊息處理
     */
    private static class ClientHandler extends Thread {
        private Socket socket;
        private boolean flag = true;

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

        @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 socketOutput = 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();
                    if ("bye".equalsIgnoreCase(str)) {
                        flag = false;
                        // 回送
                        socketOutput.println("bye");
                    } else {
                        // 列印到螢幕。並回送資料長度
                        System.out.println(str);
                        socketOutput.println("回送：" + str.length());
                    }

                } while (flag);

                socketInput.close();
                socketOutput.close();

            } catch (Exception 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());

        }