You can create basic RESTful APIs in C++ using various libraries and frameworks that facilitate HTTP communication and JSON processing. Some popular libraries and frameworks for this purpose are:

1. cpprestsdk (Microsoft C++ REST SDK):
   • A cross-platform library that provides asynchronous HTTP client and server functionality.
   • It supports JSON serialization/deserialization.
2. Crow:
   • A C++ microframework for web applications.
   • Similar to Python's Flask, Crow is easy to use for creating REST APIs.
3. Pistache:
   • A high-performance HTTP server and client library for C++.
   • Suitable for building REST APIs.
4. Boost.Beast:
   • A part of the Boost library collection.
   • Provides HTTP and WebSocket functionality.

Example: Creating a Basic RESTful API using Crow

Here's a step-by-step guide to creating a basic RESTful API using Crow:

Step 1: Install Crow

First, you need to include Crow in your project. You can do this by cloning the Crow repository and adding it to your project.

git clone <https://github.com/CrowCpp/Crow.git>

Step 2: Create a Basic API

Create a new C++ file, for example, main.cpp, and include the Crow header. Define some basic routes for your RESTful API.

#include "crow_all.h"

int main()
{
    crow::SimpleApp app;

    // Define a simple GET route
    CROW_ROUTE(app, "/")([]() {
        return "Hello, World!";
    });

    // Define a route that returns JSON
    CROW_ROUTE(app, "/json")
    ([]() {
        crow::json::wvalue x;
        x["message"] = "Hello, World!";
        return x;
    });

    // Define a route that accepts a parameter
    CROW_ROUTE(app, "/hello/<string>")
    ([](const std::string& name) {
        return "Hello, " + name;
    });

    // Define a route that accepts POST requests
    CROW_ROUTE(app, "/add").methods(crow::HTTPMethod::POST)([](const crow::request& req) {
        auto body = crow::json::load(req.body);
        if (!body)
            return crow::response(400);

        int a = body["a"].i();
        int b = body["b"].i();
        int sum = a + b;

        crow::json::wvalue res;
        res["sum"] = sum;
        return crow::response(res);
    });

    // Start the server
    app.port(18080).multithreaded().run();
}

Step 3: Build and Run

Compile your project using a C++ compiler. If you're using g++, the command might look something like this:

g++ main.cpp -o my_api -I/path/to/Crow -lpthread

Make sure to replace /path/to/Crow with the actual path to the Crow directory.

Run your application:

./my_api

Your API will now be running on port 18080. You can test the endpoints using a tool like curl or Postman.