fling

Fast and simple file transfer over network.

Overview

fling is a lightweight command-line tool for transferring files between machines over TCP. It focuses on simplicity and speed, with a clean progress bar showing transfer statistics.

Features

• Simple CLI: Just two commands - serve and send
• Fast transfers: Optimized for speed with efficient buffer handling
• Progress tracking: Real-time progress bar with transfer speed
• Security: Path traversal protection and file size validation
• Cross-platform: Works on Linux and macOS
• Lightweight: Single binary, no dependencies

Build and run

git clone https://github.com/ddoroshev/fling.git
cd fling
make
bin/fling

Requirements

• C compiler (gcc or clang)
• make
• POSIX-compliant system (Linux, macOS, *BSD)

Usage

Receiving files (server mode)

# Start server on default port (54321)
fling serve

# Start server on custom port
fling serve 8080

Sending files

# Send file to host on default port
fling send myfile.txt 192.168.1.100

# Send file to host on custom port
fling send myfile.txt 192.168.1.100 8080

Examples

On the receiving machine:

$ fling serve
Listening on 0:54321...

On the sending machine:

$ fling send document.pdf 192.168.1.100
[########################################] 100% (15.34 MB / 15.34 MB) 245.67 MB/s
File sent successfully! Completed in 0.06 seconds (245.67 MB/s avg)

Building and Testing

# Build the project
make

# Build and run tests
make test testrun

# Run tests including slow/large file tests
make testrun-slow

# Clean build artifacts
make clean

Performance

fling is optimized for speed and can achieve near-line-speed transfers on local networks. In testing, it achieves:

• ~900 MB/s on localhost transfers
• ~110 MB/s on gigabit LAN (near theoretical maximum)

Security

• Path traversal protection: Prevents directory traversal attacks in filenames
• Size validation: Verifies file sizes before and after transfer
• Input validation: Sanitizes all user inputs

Limitations

• Single file transfer only (no directory support yet)
• No encryption
• No resume capability for interrupted transfers

License

This project is licensed under the MIT License - see the LICENSE file for details.