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Python HyperDHT Examples

Encrypted P2P connections from Python, powered by hyperdht-cpp.

Requirements

  • Python 3.8+
  • Linux (x86_64 or aarch64)
  • Build tools: cmake, ninja, pkg-config
  • Libraries: libsodium, libuv

Install dependencies

# Debian / Ubuntu
sudo apt install cmake ninja-build pkg-config libsodium-dev libuv1-dev python3

# Fedora
sudo dnf install cmake ninja-build pkgconf libsodium-devel libuv-devel python3

# Arch
sudo pacman -S cmake ninja pkgconf libsodium libuv python

Build

cd examples/python
./build.sh

This builds libhyperdht.so in build-shared/ at the repo root.

Finding the library

The Python wrapper needs libhyperdht.so and libuv.so at runtime. It searches in this order:

  1. HYPERDHT_LIB env var -- explicit path to the .so file
  2. LD_LIBRARY_PATH -- standard library search path
  3. System paths -- /usr/lib, /usr/local/lib (via ldconfig)
  4. Relative to the package -- ../../build-shared/ (for development)

Pick whichever works for your setup:

# Option 1: env var (recommended for development)
export HYPERDHT_LIB=/path/to/build-shared/libhyperdht.so

# Option 2: LD_LIBRARY_PATH
export LD_LIBRARY_PATH=/path/to/build-shared:$LD_LIBRARY_PATH

# Option 3: system install
sudo cp build-shared/libhyperdht.so /usr/local/lib/
sudo ldconfig

libuv is usually already installed system-wide (libuv.so.1). If not, install it with your package manager.

Run

Quick demos (offline, no network needed)

python3 keypair_demo.py              # keypair generation + deterministic seeds
python3 hash_demo.py "hello world"   # BLAKE2b-256 hash
python3 state_demo.py                # DHT state inspection

Network demos (connects to public HyperDHT)

python3 ping_demo.py                             # ping a bootstrap node
python3 storage_demo.py put "hello from python"   # store data on the DHT
python3 storage_demo.py get <hash>                # retrieve by content hash

Server / client

# Terminal 1: start a server
python3 example.py server

# Terminal 2: connect to it
python3 example.py connect <public_key_hex>

P2P tunnel (holesail-compatible)

# Start a local web server
python3 webserver.py &

# Expose it over HyperDHT
python3 holesail_server.py --live 8080

# Connect from anywhere (JS holesail or mobile app)
holesail --connect hs://0000...

Examples

File What it does
keypair_demo.py Random, seeded, and deterministic keypair generation
hash_demo.py BLAKE2b-256 hash (same function the DHT uses internally)
state_demo.py Inspect DHT state: health, routing table, stats, suspend/resume
storage_demo.py Immutable and mutable key-value storage on the live DHT
ping_demo.py Direct UDP ping to any DHT node
example.py Server + client + keygen (the main demo)
holesail_server.py P2P tunnel server with --live, --seed, --secure
webserver.py Minimal HTTP server for holesail testing
test_wrapper.py 22 automated tests for the Python wrapper

Important: threading and callback rules

The library uses a libuv event loop internally. Three rules you must follow:

  1. Single-threaded -- all hyperdht calls must happen on the same thread that runs dht.run(). Never call stream.write(), dht.connect(), or any other library function from a background thread. If you need to bridge blocking I/O (like TCP sockets), use selectors or uv_async_send to marshal work back to the event loop thread.

  2. Wait for on_open -- after dht.open_stream(), the SecretStream header exchange must complete before you can write. The on_open callback signals readiness. Writes before on_open return error code -1. If you're bridging to a TCP socket, don't start reading from TCP until on_open fires.

  3. Callback lifetime -- keep references to all ctypes callback objects (the decorated @CFUNCTYPE functions) for as long as they might be called. If Python garbage-collects a callback while the C library still holds a pointer to it, you get a segfault.

How it works

The hyperdht/ package uses ctypes to call libhyperdht.so (the C API). No Python C extensions, no pip install, no compilation on the Python side. Just import hyperdht and go.

Testing

export HYPERDHT_LIB=../../build-shared/libhyperdht.so
python3 test_wrapper.py

Cross-language test

Start a Python server, connect from JavaScript (or vice versa):

# Python server (this machine)
python3 example.py server

# JS client (any machine with hyperdht installed)
node -e "
  const DHT = require('hyperdht')
  const d = new DHT()
  const s = d.connect(Buffer.from('<public_key>', 'hex'))
  s.on('open', () => { console.log('CONNECTED!'); d.destroy() })
"