Wordle UDP Client-Server System (C)

Overview

This project implements a client-server Wordle game in C using UDP sockets. The system consists of a non-blocking server that manages multiple concurrent game sessions and a client that communicates with the server to start games and submit guesses.

The server processes requests using a custom binary protocol and maintains per-game state, including guesses remaining and win/loss tracking.

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Features

• UDP-based client-server architecture
• Non-blocking server using fcntl and O_NONBLOCK
• Concurrent game session management using unique tokens
• Custom binary protocol for communication
• Word validation and result generation (Wordle-style feedback)
• Graceful shutdown using SIGUSR1
• Dynamic memory management (malloc, realloc, free)

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System Architecture

Server

The server:

• Listens for UDP datagrams
• Handles new game requests ("NEW")
• Assigns a unique game token per session
• Tracks active games dynamically
• Processes guesses and returns results
• Manages memory for active and completed games

Client

The client:

• Sends requests to the server
• Starts new games or submits guesses
• Parses and displays server responses

Protocol

New Game Request

• Payload: "NEW" (3 bytes)
• Response: 4-byte integer (game token)

Guess Request

• Payload:

  • 4 bytes: game token (network byte order)
  • 5 bytes: guess (string)

• Total: 9 bytes

Response

• 4 bytes: game token
• 1 byte: validity ('Y' or 'N')
• 2 bytes: guesses remaining
• 5 bytes: result string

Total: 12 bytes

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Example Usage

Compile

gcc wordle-UDP-server.c -o server
gcc wordle-client.c -o client

Run Server

./server <port> <word-file> <num-words> <seed>

Start New Game

./client localhost 8111 NEW

Submit Guess

./client localhost 8111 <token> STARE

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Key Concepts Demonstrated

• Low-level socket programming (UDP)
• Network byte order (htonl, ntohl)
• Custom protocol design
• Dynamic memory management in C
• Event-driven server loop
• Signal handling (SIGUSR1)
• Stateful session management

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File Structure

• wordle-UDP-server.c — main server implementation
• wordle-client.c — client for interacting with the server
• write-hw4-datagram.c — utility for generating test datagrams

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Future Improvements

• Add TCP support
• Implement multithreading for scalability
• Improve protocol robustness (error codes, versioning)
• Add logging and metrics
• Replace linear search with hash-based lookup for words

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