Networked Connect 4

Project Context

Developed as part of the System Programming (R3.05) module, this project aimed to transform a local Connect 4 game (built with Ebitengine) into a fully functional online multiplayer game.

The main challenge was not the game logic, but designing the “net code” allows two remote clients to synchronize their states via a central server.

Technical Architecture

The application relies on a strict Client-Server architecture where the server acts as the authority on the game flow.

1. Concurrency Management (Go)

The core of the project leverages Go’s powerful concurrency primitives:

• Goroutines: Each connected client is handled by an independent lightweight goroutine on the server side (in handlers.go), ensuring the main loop remains non-blocking.
• Channels: Heavily used for thread-safe communication between network reading processes and the game update logic (update.go).

2. Communication Protocol

We designed a custom binary protocol over TCP to minimize latency. Messages are structured as [Data Byte, Type Byte]:

• 0x01: Sending selected color (OctetPlayerColor).
• 0x02: Sending player move (column index) (OctetOpponentMove).
• 0x03: State synchronization (Ready / Waiting) (OctetOpponentState).

3. State Synchronization

The server orchestrates the different game phases to ensure both players see the same state:

• Lobby: Waiting for the second player to connect.
• Selection: Synchronizing color choices (preventing duplicate colors).
• Gameplay: Relaying moves in real-time.
• Endgame: Handling game restart (Re-match) logic.

Improvements & Extensions

Beyond the initial requirements, we enriched the application to enhance the multiplayer experience:

Architecture & Network

• Concurrent Handling: The server manages each client in a dedicated goroutine, effectively separating game logic from network communication management.
• Easy Configuration: Implemented a startup screen for Server IP input (replacing the previous command-line flag method).

Advanced Synchronization (Selection Phase)

We made the color selection screen interactive in real-time:

• Visualization: The opponent’s cursor movements are visible live while they are making their selection.
• Game Constraints: Locking system preventing both players from picking the same color.
• Flexibility: Ability to change color selection as long as the opponent hasn’t confirmed theirs.