📡 minitalk

📝 Introduction

minitalk is a 42 School project focused on creating a small data exchange program using UNIX signals. The project consists of a client and server that communicate using only SIGUSR1 and SIGUSR2 signals.

"A simple but powerful implementation of inter-process communication using signals."

The goal is to transmit any string from a client program to a server program using only UNIX signals as the communication method.

🎯 Project Objectives

• Implement a communication protocol using only UNIX signals
• Create a client that can send messages to a server
• Create a server that can receive and display messages
• Handle the transmission of strings of any length
• Implement proper error handling and signal management
• Learn about processes, signals, and bitwise operations

🧩 Project Structure

The project consists of three main components:

minitalk/
├── inc/
│   └── minitalk.h  # Header file with prototypes and includes
├── src/
│   ├── client.c    # Client implementation
│   └── server.c    # Server implementation
└── Makefile        # Compilation instructions

🛠️ Implementation Details

minitalk.h

The header file includes:

• Standard library includes
• Custom function prototypes
• Wait time definition for signal transmission
• Utility function declarations

client.c

The client program sends messages to the server:

Function	Description
pid_error	Validates command line arguments and PID format
send_ch_by_bit	Sends a single character by breaking it into 8 bits
send_len_by_bit	Sends string length as 32 bits to prepare the server
main	Parses arguments and orchestrates the message transmission

server.c

The server program receives and displays messages from clients:

Function	Description
recive_len	Reconstructs the length of the incoming message from bits
recive_str	Reconstructs characters from bits and builds the final string
recive_client_data	Signal handler that processes incoming signals
main	Displays PID, sets up signal handlers, and waits for client connections

💡 Communication Protocol

1. Connection Establishment:

   • Server starts and displays its PID
   • Client uses the server's PID to target signal transmission

2. Message Transmission:

   • Client first sends the string length (32 bits) to the server
   • Server allocates memory based on the received length
   • Client sends each character of the string (8 bits per character)
   • Server reconstructs each character and builds the complete message

3. Bit Encoding:

   • SIGUSR1 represents bit value 1
   • SIGUSR2 represents bit value 0
   • Bits are sent sequentially with a delay between signals

🔍 Key Features

• Binary data transmission using only two signals
• Support for messages of any length
• Error handling for invalid PIDs
• Memory management for received strings
• Bitwise operations for encoding/decoding messages

🧠 Skills Developed

• Process management and inter-process communication
• Signal handling in UNIX systems
• Bitwise operations and binary data manipulation
• Memory management
• Protocol design and implementation

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📊 Project Stats

Metric	Value
Final Score	80/100
Lines of Code	~150
Signal Types	2 (SIGUSR1, SIGUSR2)