请接着给出服务器端对应的具体代码

以下是服务器端对应的具体代码示例：

import java.net.*;
import java.io.*;

public class TicTacToeServer {
    private ServerSocket serverSocket = null;
    private Socket player1 = null;
    private Socket player2 = null;
    private char[][] board = new char[3][3];
    private int currentPlayer = 1;
    private PrintWriter[] outs = new PrintWriter[2];

    public TicTacToeServer(int port) {
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Server started: " + serverSocket);
        } catch (IOException e) {
            System.out.println("Could not listen on port: " + port);
            System.exit(-1);
        }
    }

    public void acceptPlayers() {
        try {
            System.out.println("Waiting for players...");
            player1 = serverSocket.accept();
            System.out.println("Player 1 connected: " + player1);
            outs[0] = new PrintWriter(player1.getOutputStream(), true);
            outs[0].println("WELCOME 1");
            player2 = serverSocket.accept();
            System.out.println("Player 2 connected: " + player2);
            outs[1] = new PrintWriter(player2.getOutputStream(), true);
            outs[1].println("WELCOME 2");
        } catch (IOException e) {
            System.out.println("Accept failed: " + serverSocket);
            System.exit(-1);
        }
    }

    public void playGame() {
        try {
            BufferedReader[] ins = new BufferedReader[2];
            ins[0] = new BufferedReader(new InputStreamReader(player1.getInputStream()));
            ins[1] = new BufferedReader(new InputStreamReader(player2.getInputStream()));
            String[] names = {"Player 1", "Player 2"};
            String inputLine;
            while (true) {
                int row = -1;
                int col = -1;
                do {
                    outs[currentPlayer - 1].println("YOUR_MOVE");
                    inputLine = ins[currentPlayer - 1].readLine();
                    String[] move = inputLine.split(" ");
                    row = Integer.parseInt(move[0]);
                    col = Integer.parseInt(move[1]);
                } while (!isValidMove(row, col));
                board[row][col] = (currentPlayer == 1) ? 'X' : 'O';
                outs[currentPlayer - 1].println("VALID_MOVE");
                outs[currentPlayer - 1].println(getBoard());
                if (isWinner(currentPlayer)) {
                    outs[currentPlayer - 1].println("VICTORY");
                    outs[(currentPlayer % 2)].println("DEFEAT");
                    break;
                } else if (isBoardFull()) {
                    outs[0].println("TIE");
                    outs[1].println("TIE");
                    break;
                }
                currentPlayer = (currentPlayer % 2) + 1;
            }
        } catch (IOException e) {
            System.out.println("Error during game: " + e.getMessage());
        }
    }

    private boolean isValidMove(int row, int col) {
        if (row < 0 || row >= 3 || col < 0 || col >= 3) {
            return false;
        }
        if (board[row][col] != '\0') {
            return false;
        }
        return true;
    }

    private boolean isWinner(int player) {
        char symbol = (player == 1) ? 'X' : 'O';
        for (int i = 0; i < 3; i++) {
            if (board[i][0] == symbol && board[i][1] == symbol && board[i][2] == symbol) {
                return true;
            }
            if (board[0][i] == symbol && board[1][i] == symbol && board[2][i] == symbol) {
                return true;
            }
        }
        if (board[0][0] == symbol && board[1][1] == symbol && board[2][2] == symbol) {
            return true;
        }
        if (board[0][2] == symbol && board[1][1] == symbol && board[2][0] == symbol) {
            return true;
        }
        return false;
    }

    private boolean isBoardFull() {
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                if (board[i][j] == '\0') {
                    return false;
                }
            }
        }
        return true;
    }

    private String getBoard() {
        String s = "";
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                s += board[i][j];
            }
            s += "\n";
        }
        return s;
    }

    public static void main(String[] args) {
        TicTacToeServer server = new TicTacToeServer(5000);
        server.acceptPlayers();
        server.playGame();
    }
}

上述代码实现了服务器端的功能，包括监听客户端连接、处理游戏逻辑、发送游戏状态更新等。其中，`acceptPlayers()` 方法用于等待两个客户端连接，并向客户端发送欢迎消息；`playGame()` 方法用于处理游戏逻辑，包括等待客户端下棋请求、检查请求的合法性、更新游戏状态和发送游戏状态更新消息等。在 `playGame()` 方法中，使用 `BufferedReader` 和 `PrintWriter` 实现了服务器端与客户端的通信。 `isValidMove()` 方法用于检查下棋请求是否合法，`isWinner()` 方法用于检查当前玩家是否获胜，`isBoardFull()` 方法用于检查棋盘是否填满，`getBoard()` 方法用于获取当前的棋局状态。在 `main()` 方法中，创建了一个 `TicTacToeServer` 对象并调用其方法以启动服务器。