Connect Four Game as a Linux Kernel Module

Overview

FourInARow is a Linux kernel module that implements a virtual character device (/dev/fourinarow) to simulate the Connect Four game. This device allows users to play against a computer opponent using read and write operations from userspace. The computer player selects moves randomly, while the kernel module handles game logic, board state, and win/tie detection.

Project Structure

• project-base/: Linux kernel environment.
• KernelGame/: Contains the fourinarow kernel module source code and related files.

Features

• Linux Kernel Module named fourinarow.ko
• Character device interface: /dev/fourinarow
• Fully working 8x8 Connect Four game against a computer
• Kernel-space game logic with input/output via read() and write()
• Win and tie detection

Implementation

• The device node uses chmod 666 to provide read and write permissions for all users.
• All supported module commands are implemented in the dev_write function.
• The DROPC command allows the user to drop their piece into the specified column. It places the piece in the lowest available row within that column.
• The CTURN command makes the computer perform a random move, dropping its piece into a randomly chosen column that has space.
• The checkWin function checks for a winning condition by scanning horizontally, vertically, and diagonally. It is invoked after each DROPC and CTURN move.
• The checkTie function verifies if the board is full and no winner has been determined, resulting in a tie.
• The RESET command must be used to reset the board and to select the user’s playing color ('Y' for yellow or 'R' for red).
• Module initialization involves setting up the kernel module, registering the character device, and creating the corresponding device class and device node

Module Commands

• Interact with the game using write() to /dev/fourinarow, and reads responses via read().

RESET $

• Initializes or resets the game.
• $ is either R (Red) or Y (Yellow) – the user's color.
• Response: OK

BOARD

• Returns the current board state.
• Response: Board grid

DROPC $

• Drops user's chip in column $ (A–H).
• Responses:
  • OK: Move accepted
  • OOT: Out of turn
  • NOGAME: No active game
  • WIN: You won
  • TIE: Tie game

CTURN

• Requests the computer to make its move.
• Responses:
  • OK: Computer moved
  • OOT: Not computer’s turn
  • NOGAME: No active game
  • LOSE: Computer won
  • TIE: Tie game

File Structure

• fourinarow.ko: Compiled kernel module
• /dev/fourinarow: Character device interface
• fourinarow.c: Source code implementing module functionality

Building & Loading the Module

make
sudo insmod fourinarow.ko

Sample Usage

# Start a new game as Yellow
echo "RESET Y" >> /dev/fourinarow
cat /dev/fourinarow  # -> OK

# Drop a chip in column B
echo "DROPC B" >> /dev/fourinarow
cat /dev/fourinarow  # -> OK, WIN, or TIE

# Let computer take a turn
echo "CTURN" >> /dev/fourinarow
cat /dev/fourinarow  # -> OK, LOSE, or TIE

# Check board state
echo "BOARD" >> /dev/fourinarow
cat /dev/fourinarow # -> Board Grid

Removing Module

sudo rmmod fourinarow
make clean