OpenDHT

A lightweight C++17 Distributed Hash Table implementation.

OpenDHT provides an easy to use distributed in-memory data store. Every node in the network can read and write values to the store. Values are distributed over the network, with redundancy.

• Lightweight and scalable, designed for large networks and small devices
• High resilience to network disruption
• Public key cryptography layer providing optional data signature and encryption (using GnuTLS)
• IPv4 and IPv6 support
• Clean and powerful C++17 map API
• Bindings for C, Rust & Python 3
• REST API with optional HTTP client+server with push notification support

Documentation

See the wiki: https://github.com/savoirfairelinux/opendht/wiki

How to run a node

You can help contribute to the public network by running a stable node with a public IP address. https://github.com/savoirfairelinux/opendht/wiki/Running-a-node-with-dhtnode

How-to build and install

Build instructions: see BUILD.md

Examples

C++ example

The tools directory includes simple example programs :

• dhtnode, a command line tool, allowing to run a DHT node and perform operations supported by the library (get, put etc.) with text values.
• dhtchat, a very simple IM client working over the dht.

Example program launching a DHT node, connecting to the network and performing some basic operations:

#include <opendht.h>
#include <vector>

int main()
{
    dht::DhtRunner node;

    // Launch a dht node on a new thread, using a
    // generated RSA key pair, and listen on port 4222.
    node.run(4222, dht::crypto::generateIdentity(), true);

    // Join the network through any running node,
    // here using a known bootstrap node.
    node.bootstrap("bootstrap.jami.net", "4222");

    // put some data on the dht
    std::vector<uint8_t> some_data(5, 10);
    node.put("unique_key", some_data);

    // put some data on the dht, signed with our generated private key
    node.putSigned("unique_key_42", some_data);

    // get data from the dht
    node.get("other_unique_key", [](const std::vector<std::shared_ptr<dht::Value>>& values) {
        // Callback called when values are found
        for (const auto& value : values)
            std::cout << "Found value: " << *value << std::endl;
        return true; // return false to stop the search
    });

    // wait for dht threads to end
    node.join();
    return 0;
}

Python 3 example

Install on Linux, macOS and Windows with:

pip install opendht

Using the simple, blocking API:

import opendht as dht

node = dht.DhtRunner()
node.run()

# Join the DHT network through any running node,
# here using a known bootstrap node.
node.bootstrap("bootstrap.jami.net", "4222")

# blocking call (provide callback arguments to make the call non-blocking)
node.put(dht.InfoHash.get("unique_key"), dht.Value(b'some binary data'))

results = node.get(dht.InfoHash.get("unique_key"))
for value in results:
    print(value)

Or using asyncio:

import asyncio
import opendht.aio as dht

async def dht_async_demo(key_str: str):
    # Start a new node using an async context manager.
    # It is also possible to call run()/await shutdown() manually.
    async with dht.DhtRunner(
        bootstrap=(("bootstrap.jami.net", "4222"),)
    ) as node:
        # compute key hash
        key = dht.InfoHash.get(key_str)

        # put data, waiting for completion
        await node.put(key, dht.Value(b'tata data'))

        # get all values at key
        results = await node.getAll(key)
        for value in results:
            print(value)
        
        # same operation, but stream values as they come from the network
        with node.get(key) as results:
            async for value in results:
                print(value)

        # listen for change of values at key
        with node.listen(key) as values:
            async for value, expired in values:
                print(value)
                if value.data == b'tata data':
                    break

asyncio.run(dht_async_demo("unique_key"))

Dependencies

Core dependencies:

• msgpack-c 1.2+, used for data serialization.
• GnuTLS 3.3+, used for cryptographic operations.
• Nettle 2.4+, a GnuTLS dependency for crypto.
• {fmt} 9.0+, for log formatting.

Optional dependencies for the REST API (DHT proxy client/server):

• (optional) restinio
• (optional) llhttp
• (optional) jsoncpp 1.7.4-3+
• (optional) simdutf

Build environment:

• Build tested with GCC 9+ (GNU/Linux, Windows with MinGW), Clang/LLVM (GNU/Linux, Android, macOS, iOS).
• Build tested with Microsoft Visual Studio 2019, 2022

License

Copyright (c) 2014-2026 Savoir-faire Linux Inc.

OpenDHT is released under the MIT License. See LICENSE for details.

Acknowledgements

This project was originally based on https://github.com/jech/dht by Juliusz Chroboczek.