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 contributing 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: https://github.com/savoirfairelinux/opendht/wiki/Build-the-library

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

import opendht as dht

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

# Join the 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 r in results:
    print(r)

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) restinio used for the REST API.
• (optional) llhttp used for the REST API.
• (optional) jsoncpp 1.7.4-3+, used for the REST API.
• Build tested with GCC 7+ (GNU/Linux, Windows with MinGW), Clang/LLVM (GNU/Linux, Android, macOS, iOS).
• Build tested with Microsoft Visual Studio 2019, 2022

Contact

IRC: join us on Libera.chat at #opendht.

License

Copyright (C) 2014-2023 Savoir-faire Linux Inc.

OpenDHT is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

See COPYING or https://www.gnu.org/licenses/gpl-3.0.en.html for the full GPLv3 license.

Acknowledgements

This project was originally based on https://github.com/jech/dht by Juliusz Chroboczek. It is independent from another project called OpenDHT (Sean Rhea. Ph.D. Thesis, 2005), now extinct.