File Transfer Application

A secure client-server file transfer system with authentication, resumable downloads, and access control.

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Table of Contents

• Features
• Prerequisites
• Installation
• Usage
• Configuration
• Security
• Troubleshooting
• Contributing
• License

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Features

• 🔐 Secure password hashing (SHA-256)
• 🔄 Resumable file transfers
• 🌐 File visibility options (Public/Private)
• 🔑 Access code protection for private files
• 📊 Transfer progress tracking
• 🖥️ Server administration console
• 🧾 User transaction history
• 👥 Concurrent client support

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Prerequisites

• Linux environment
• GCC compiler
• SQLite3 development libraries
• OpenSSL libraries
• pthread support

For Ubuntu/Debian:

sudo apt-get install build-essential libsqlite3-dev libssl-dev

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Installation

Clone the repository: git clone https://github.com/MeegadaVamsidhar/File_Sharing_System_OS.git

Compile the project:

make        # Build both server and client
make server # Build only the server
make client # Build only the client
make clean  # Remove binaries

Makefile Sample:

CC = gcc
CFLAGS = -Wall -Wextra
LDFLAGS = -pthread -lsqlite3 -lcrypto

all: server client

server: src/server.c
	$(CC) $(CFLAGS) src/server.c -o server $(LDFLAGS)

client: src/client.c
	$(CC) $(CFLAGS) src/client.c -o client $(LDFLAGS) -lcrypto

clean:
	rm -f server client

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Usage

Start the Server

./server

Run the Client

./client <server_ip>

Example:

./client 127.0.0.1

Basic Client Commands

/upload <filename>      # Upload a file
/download <filename>    # Download a file
/list                   # List server files
/locallist              # List local files
/help                   # Show help menu

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Configuration

Server Settings

• Port: Change PORT in server.c (default: 8080)
• Max Clients: Modify MAX_CLIENTS in server.c
• File Storage: Update files/ directory in server.c

Client Settings

• Download Directory: Modify DOWNLOAD_FOLDER in client.c
• Buffer Size: Adjust BUFFER_SIZE for transfers

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Security

• 🔐 Passwords hashed using SHA-256
• 🚫 Input validation during authentication
• 🔏 Access code enforcement for private files
• 🛡️ SQL injection prevention
• 🔍 File integrity checks
• 💼 Basic session management

Security Notes:

• Passwords are never stored or transmitted in plain text
• Access codes are encrypted in the database
• Use only in protected/internal networks (not production-ready)
• For production, add SSL/TLS encryption

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Troubleshooting

Missing Dependencies?

sudo apt-get install libsqlite3-dev libssl-dev

Connection Issues?

• Is the server running?
• Are the firewall rules correct?
• Is the server IP valid?

File Permission Issues?

chmod +x server client
mkdir -p files client_downloads

Database Errors?

rm users.db  # ⚠️ WARNING: Deletes all user data

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Contributing

1. Fork the repository
2. Create a feature branch:

   git checkout -b feature/your-feature

3. Commit your changes
4. Push to your branch
5. Open a Pull Request

Development Guidelines:

• Use C99 standard
• Maintain consistent code formatting
• Document any new functions
• Test thoroughly
• Keep commits focused and atomic

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License

This project is licensed under the MIT License.