NGHOST

NGHOST is a LAN-first peer-assisted file downloader written in Go.

It allows machines on the same local network to automatically share already-downloaded files with each other, reducing repeated internet downloads and improving download speeds on shared networks such as:

• college Wi-Fi
• hostels
• labs
• offices
• maker spaces

Instead of every machine downloading the same file separately from the internet, NGHOST checks whether another peer on the LAN already has the file and downloads it locally.

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Infrastructure

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Video Demo (using two devices on one LAN)

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How It Works

LAN-First Download Flow

When downloading a file:

1. The client downloads only the first 1 MB from the internet

2. A SHA256 hash of that chunk is computed

3. The LAN is scanned using mDNS for NGHOST peers

4. Each peer is queried:

   • “Do you have a file matching this hash?”

5. If a peer has the file:

   • the full file is downloaded over LAN

6. Otherwise:

   • download falls back to the internet

This dramatically reduces WAN bandwidth usage when many users download the same files.

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Features

• LAN peer discovery using mDNS
• SHA256 content-addressable lookup
• Partial-hash matching using first 1 MB
• SQLite-based file index
• Automatic directory scanning
• HTTP-based file serving
• Internet fallback when LAN misses
• Resume support for servers with HTTP Range requests
• Zero central server required

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Architecture

Daemon

The daemon:

• scans a shared directory
• computes hashes
• stores metadata in SQLite
• advertises itself over mDNS
• serves files over HTTP

Endpoints:

• /has/<full_sha256>
• /hasfirst/<first1mb_sha256>

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Client

The client:

• discovers peers over mDNS
• checks LAN availability
• downloads from peers when possible
• falls back to internet when needed

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Project Structure

nghost/
├── client/
│ └── main.go (client code)
├── daemon/
│ ├── main.go (daemon code should be run on background with systemctl)
│ ├── conf.json │ └── files.db (generated by the daemon at runtime)
├── go.mod
└── go.sum

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Installation

Requirements

• Go 1.22+
• SQLite3

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Clone

git clone https://github.com/lsnnt/nghost.git
cd nghost
go mod tidy

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Build

Daemon

go build -o daemon ./daemon

Client

go build -o client ./client

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Configuration

Create conf.json inside daemon/:

{
"DDir": ["/path/to/shared/files"]
}

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Running

Start Daemon

cd daemon
./daemon

Make sure conf.json is in same folder as daemon The daemon will:

• start HTTP server on port 14920 (normal ports may be occupied so)
• advertise itself via mDNS
• scan files every 30 seconds

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Download by URL

./client -url https://example.com/file.iso

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Download by Full SHA256

./client -hash <sha256>

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Custom Output File

./client -url https://example.com/file.iso -o ubuntu.iso

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Example Workflow

Student A downloads:

ubuntu-24.04.iso

The daemon indexes the file and advertises availability on the LAN.

Later, Student B runs:

./client -url https://releases.ubuntu.com/ubuntu-24.04.iso

Instead of downloading from the internet again, the file is transferred directly over the LAN.

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Security

NGHOST is designed for trusted local networks and cooperative file sharing.

Current implementation:

• no authentication
• no encryption
• no access control

Do not expose the daemon directly to the public internet.

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Why?

Shared networks often suffer from repeated downloads of identical large files:

• Linux ISOs
• datasets
• game installers
• lecture videos
• development tools

NGHOST reduces redundant internet traffic by turning the LAN itself into a cooperative cache.

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Limitations

This is a LAN project so it will only work if some other user in the same LAN is running the daemon and they have the file avaliable otherwise it will work as a normal downloader.

Ai Disclosure

This code is Ai-Assisted but if you cannot understand any function just contact me.

Inspiration

Idea and inspiration from : https://github.com/PurviMalhotra/Ghost