🕹️ Tic Tac Toe Backend with Ktor & WebSockets

This is the backend server for a real-time two-player Tic Tac Toe game built using:

• 🖥️ Ktor (Kotlin) backend with WebSockets
• 🧠 Kotlin Serialization & StateFlow for reactive state management
• 🚀 Deployed on a VPS with port forwarding

It handles all game logic, player turns, win/draw detection, and broadcasting of game state to connected clients.
The backend is designed to work with any WebSocket-compatible frontend (Android, web, desktop).

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📦 Tech Stack

🔙 Backend (Ktor - IntelliJ IDEA)

• Kotlin-based Ktor server
• WebSockets for real-time communication
• JSON serialization via kotlinx.serialization
• State management with StateFlow
• /play WebSocket endpoint
• Deployable to VPS or cloud hosting

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⚙️ Features

✅ Real-time two-player Tic Tac Toe
✅ Automatic game reset after win/draw
✅ Server-controlled game logic (prevents cheating)
✅ Lightweight WebSocket message protocol
✅ Clean separation of logic, models, and networking code
✅ Easily deployable for online play

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🧪 How It Works

• The backend:

  • Assigns players as X or O in connection order
  • Validates moves (right turn, empty cell, game ongoing)
  • Detects win or draw
  • Broadcasts the full GameState JSON to both players after every move
  • Resets the board after a short delay when the game ends

• Communication format:

  MakeTurn#{"x":0,"y":2}

• Example game state broadcast:

  {
    "playerTurn": "O",
    "field": [["X", null, "O"], [null, "X", null], [null, null, "O"]],
    "winningPlayer": null,
    "isBoardFull": false,
    "connectedPlayers": ["X","O"]
  }

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🚀 Getting Started

🖥️ Backend (Local Run)

1. Clone the repository:

   git clone https://github.com/your-username/tictactoe-backend.git
   cd tictactoe-backend

2. Run the server:

   ./gradlew run

3. Connect via WebSocket:

   ws://localhost:8080/play

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🌐 Deployment

1. Build a fat JAR:

   ./gradlew shadowJar

2. Upload to VPS:

   java -jar build/libs/tictactoe-backend-all.jar

3. Open firewall port (default: 8080)
4. Update your frontend WebSocket URL to:

   ws://<your-server-ip>:8080/play
   

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🔐 Security Note

• No authentication is implemented yet — it is intended in future updates.

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💡 Possible Improvements

• Game lobby & matchmaking
• Player names & avatars
• Persistent scoreboard
• Spectator mode
• Multiple simultaneous games

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📚 Credits

• Ktor Official Documentation

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MIT License

Copyright (c) 2025 Nikunj Patel

This project is MIT licensed.