Question

(Modifications to the Multithreaded Tic-Tac-Toe Program) The programs in Figs. 24.13 and 24.15 implemented a multithreaded, client/server version of the game of Tic- Tac-Toe. Our goal in developing this game was to demonstrate a multithreaded server that could process multiple connections from clients at the same time. The server in the example is really a mediator between the two client applets - it makes sure that each move is valid and that each client moves in the proper order. The server does not determine who won or lost or whether there was a draw. Also, there is no capability to allow a new game to be played or to terminate an existing game. The following is a list of suggested modifications to Figs. 24.13 and 24.15: a) Modify the TicTacToeServer class to test for a win, loss or draw on each move in the game. Send a message to each client applet that indicates the result of the game when the game is over. b) Modify the TictactoeC 7 ient class to display a button that when clicked allows the client to play another game. The button should be enabled only when a game completes. Note that both class TictactoeC 7 ient and class TictactoeServer must be modified to reset the board and all state information. Also, the other TicTacToeClient should be notified that a new game is about to begin so that its board and state can be reset. c) Modify the TictactoeCl ient class to provide a button that allows a client to terminate the program at any time. When the user clicks the button, the server and the other client should be notified. The server should then wait for a connection from another client so that a new game can begin. d) Modify the TictactoeCl ient class and the TicTacToeServer class so that the winner of a game can choose game piece \(\mathrm{X}\) or \(\mathrm{O}\) for the next game. Remember: \(\mathrm{X}\) always goes first. e) If you would like to be ambitious, allow a client to play against the server while the server waits for a connection from another client.

Short answer

Modify classes to evaluate win/lose/draw, reset for new games, allow termination, let winners choose the next game piece, and implement single-player mode.

Step-by-step solution

Modify Server to Determine Game Result

In the `TicTacToeServer` class, add functionality to check for a win, loss, or draw after each move. This typically involves checking rows, columns, and diagonals for any three identical non-empty symbols. Once the game result is determined, send a message to both clients informing them of the game's outcome.

Add Button for New Game in Client

Enhance the `TicTacToeClient` class by adding a button that allows users to initiate a new game. This button should be enabled only when a game is completed. Modify the client-server communication to manage the board reset and notify both clients to start a new game.

Implement Program Termination Feature

In the `TicTacToeClient`, introduce a button that can terminate the current game. When this button is clicked, the client should notify the server and other client. The server needs to handle this by potentially initiating a wait state for a new player to join.

Adjust Game Piece Selection Based on Winning

Modify both the `TicTacToeClient` and `TicTacToeServer` classes to allow the winner of the previous game to select their game piece (either X or O) for the next game. Ensure that the server confirms this choice and communicates it to both clients.

Enable Single Player Mode Against Server

If desired, enhance the server to allow a client to play against it while waiting for another client. Implement basic AI for the server to make moves as second player, ensuring that the AI's moves are valid. This creates a single-player mode option.

Key concepts

Client-Server Architecture

A client-server architecture is a network design used in computer game development to allow multiple clients (users) to interact with a central server. It's the foundational framework used for many online games, including our Tic-Tac-Toe game. The server acts as a mediator, handling communication between multiple clients to ensure smooth gameplay. This setup is essential in our example to facilitate turn-taking and validate each move.

• The server manages connections from multiple clients, ensuring each player takes turns.
• It validates each move to ensure it's legitimate and follows the game's rules.
• If any client wants to restart the game, the server coordinates to reset the game board and notify all players involved.

In effect, the server plays a central role in managing game state and continuity so all players have a synchronized view. This architecture is common in various applications beyond gaming, as it efficiently handles multiple connections and processes data centrally.

Game Development

Game development is the process of designing and creating games. In the context of our exercise, developing a multithreaded Tic-Tac-Toe game involves programming both logic and interaction elements. The game must function smoothly for two users simultaneously, each on a separate client.

• This involves implementing rules for games like detecting a win, loss, or draw, which are checked every move.
• User interface elements like buttons are added to reset the game or terminate it, enhancing user control and interaction.
• Since this is a client-server setup, communication between clients and the server is a critical part of the development process.

This exercise specifically highlights the need for coordination in game development, ensuring that all components work seamlessly together. The goal is to offer a coherent experience, where users can interact with game elements while the system manages the underlying processes like threading and communication.

Concurrency Control

Concurrency control is essential in multithreaded programming, allowing multiple processes to run simultaneously without interfering with each other. In the Tic-Tac-Toe game, concurrency is crucial to handling actions from clients who are making moves at the same time. By using threads, the server can manage multiple client connections concurrently, creating a seamless gaming experience.

• Each client’s move is a separate event, managed by a thread to ensure it's processed independently.
• The server uses concurrency controls to maintain the correct sequence of moves, ensuring the game's turn order is respected.
• Synchronization techniques are applied to prevent data inconsistencies, such as two players moving simultaneously.

Efficient concurrency handling ensures that all game rules are followed, maintaining a fair game state. This is an important concept, especially when building applications that require responsiveness and efficiency in real-time scenarios.

Java Programming

Java programming plays a pivotal role in developing our multithreaded Tic-Tac-Toe game. Known for its "write once, run anywhere" capability, Java is highly used for networked applications due to its robust threading model and network libraries.

• The game uses Java's thread class to handle multiple clients connecting to the server simultaneously.
• Java's object-oriented principles allow for modular game design, making it easy to update game logic and functionalities like a win-checking mechanism.
• Network capabilities are facilitated by Java's socket programming, helping create a stable link between the server and the numerous clients.

With these features, Java provides the tools necessary to develop efficient and scalable networked games. The language's stability and extensive libraries support complex game logics, making it a preferred choice for client-server game applications.