How-to Guide: Interfacing with Bitcoin Core using C++

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This comprehensive guide will walk you through the process of programmatically interfacing with bitcoin Core using the C++ programming language. We’ll cover the fundamental concepts, essential tools, and provide practical, step-by-step code examples to help you build your own Bitcoin applications.

Bitcoin Core, the reference implementation of the Bitcoin protocol, offers a powerful JSON-RPC interface. This interface allows developers to interact with a running Bitcoin node, enabling a wide range of functionalities from querying blockchain data to managing wallets. C++ is an excellent choice for this task due to its performance, control, and extensive ecosystem of libraries.

Prerequisites

Before you begin, ensure you have the following components and knowledge in place:

  • Bitcoin Core Installed and Running:

    You need a functional Bitcoin Core node. For development and testing purposes, running Bitcoin Core in “regtest” mode is highly recommended. This mode allows for rapid iteration and testing without any risk to the live Bitcoin network or your actual funds.

    • Starting in Regtest Mode:

      Open your terminal or command prompt and execute the following command:

    • Configuration for RPC Access:

      To enable programmatic interaction, configure your Bitcoin Core node to accept RPC connections. Edit your file (typically located in your Bitcoin data directory) and add these lines:

      Remember to replace and with strong, unique credentials. The setting restricts RPC access to your local machine, which is a good security practice.

  • C++ Compiler:

    A modern C++ compiler is essential. Popular choices include GCC, Clang, and Microsoft Visual C++ (MSVC). Ensure your compiler supports C++17 or later for optimal compatibility with modern libraries.

  • JSON Library:

    Bitcoin Core’s RPC interface communicates using JSON. You will need a C++ library capable of parsing and generating JSON data. Highly recommended options include:

    • nlohmann/json: A header-only, modern C++ JSON library. It’s celebrated for its ease of use, intuitive API, and excellent documentation, making it a top choice for many developers.

    • jsoncpp: A well-established and robust C++ JSON library.

    • RapidJSON: Known for its exceptional performance and low memory overhead.

    For the examples in this guide, we will primarily utilize nlohmann/json due to its simplicity and widespread adoption.

  • HTTP Client Library:

    To send HTTP requests to the Bitcoin Core RPC server, you’ll need a C++ HTTP client library. Consider these popular choices:

    • cpp-httplib: A header-only HTTP/HTTPS server and client library. It’s remarkably easy to integrate and use, making it ideal for rapid development.

    • libcurl: A mature and widely used C library for data transfer with URL support. C++ bindings are readily available.

    • Boost.Beast: A powerful and flexible HTTP library built on top of Boost.Asio, offering advanced networking capabilities.

    This guide will use cpp-httplib for its straightforward implementation and minimal setup.

Understanding the Bitcoin Core RPC Interface

Bitcoin Core exposes its extensive functionality through a standardized JSON-RPC 2.0 API. Each interaction with the node involves sending a JSON-formatted request and receiving a JSON-formatted response.

A typical JSON-RPC request object includes:

  • : Specifies the JSON-RPC protocol version (commonly “1.0” or “2.0”).
  • : The name of the RPC command you wish to execute (e.g.,, ).
  • : An array containing the arguments required by the specified method.
  • : A unique identifier for the request, used to match requests with their corresponding responses.

The response from Bitcoin Core will also be a JSON object, typically containing:

Step-by-Step Implementation

Let’s break down the process of creating a C++ Bitcoin Core RPC client into manageable steps.

Step 1: Project Setup

  • Create a New C++ Project:

    Initialize a new C++ project using your preferred Integrated Development Environment (IDE) or build system (e.g., CMake, Make).

  • Include Necessary Libraries:

    Make the header files for your chosen JSON and HTTP client libraries accessible

Further Reading