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 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.
(optional) restinio 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 2017, 2019, 2022

Contact

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

License

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.

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