📡 send-file

A lightweight client/server file transfer system written in C++ using raw TCP sockets, with chunked streaming and a simple XOR-based encryption layer.

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✨ Features

• Custom TCP client/server implementation (single binary mode)
• Chunked file transfer over sockets
• XOR-based encryption/decryption layer
• Configurable packet size
• File integrity check via system MD5
• Packet-level debug output (useful for learning/debugging)

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📁 Project Structure

send-file/
│
├── include/
│   ├── network.h
│   ├── file_io.h
│   ├── crypto.h
│   └── util.h
│
├── src/
│   ├── main.cpp
│   ├── network.cpp
│   ├── file_io.cpp
│   ├── crypto.cpp
│   └── util.cpp
│
├── test.txt
├── Makefile
└── README.md

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⚙️ Build Instructions

Compile

make

Clean build

make clean

This produces:

sendfile

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🚀 Usage

Start server

./sendfile server

You will be prompted for:

• Port number
• Output file name
• Encryption key

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Start client

./sendfile client

You will be prompted for:

• Server IP address
• Port number
• File to send
• Packet size (bytes)
• Encryption key

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🔁 Example Workflow

Terminal 1 (Server)

./sendfile server

Port#: 8080
Save file to: output.txt
Enter encryption key: test

Terminal 2 (Client)

./sendfile client

Connect to IP address: 127.0.0.1
Port#: 8080
File to be sent: test.txt
Pkt size: 1024
Enter encryption key: test

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🔐 Encryption

This project uses a simple XOR cipher:

• Same key is used for encryption and decryption
• Applied before sending and after receiving
• Intended for learning purposes, not security

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🧠 How it works

1. Client reads file into memory
2. File is encrypted using XOR key
3. Data is sent in fixed-size packets over TCP
4. Server receives and reconstructs file
5. Server decrypts using same key
6. Output file is written to disk

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🧪 Quick Test

You can test locally using the included sample file:

test.txt

Steps

1. Start the server:

./sendfile server

2. In another terminal, run the client:

./sendfile client

3. Use:

• IP: 127.0.0.1
• Same port on both
• Same encryption key on both
• File: test.txt

This will transfer the file locally and verify the full workflow.

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🧪 Notes

• Server must be started before client
• Same port and encryption key must be used on both sides
• Designed for local network / learning purposes
• Not intended for production use

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🛠️ Tech Stack

• C++
• POSIX sockets
• Linux system calls
• XOR cipher (custom implementation)
• Makefile build system

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📌 Purpose

This project was built to explore:

• Low-level networking in C++
• File streaming over TCP
• Manual memory management
• Basic encryption techniques
• System-level programming concepts