HTTP Client for C++: Top Libraries for Networking

HTTP Client for C++: Overview of the Best Libraries

When developing modern applications in C++, the need often arises to interact with web servers via the HTTP protocol. Whether it's downloading data from an API, sending forms, or exchanging JSON messages, a reliable HTTP client is essential. Unlike many modern languages, the C++ standard library does not include built-in tools for working with HTTP. Fortunately, there are several mature and high-performance libraries that solve this problem. In this article, we will look at four of the best HTTP clients for C++, compare their features, and provide practical examples.

1. libcurl (cURL)

libcurl is arguably the most popular and time-tested library for transferring data over various protocols, including HTTP/1.1 and HTTP/2. It is written in C but has excellent wrappers for C++ (e.g., curlpp). libcurl is used in thousands of projects, from embedded systems to server applications.

Key Features:

• Support for HTTP, HTTPS, FTP, SMTP, and many other protocols.
• SSL/TLS support (OpenSSL, Schannel, NSS).
• Asynchronous requests via the multi interface.
• Flexible configuration of headers, cookies, proxies, timeouts.
• Cross-platform (Windows, Linux, macOS, mobile OS).

Simple GET request example using the C++ wrapper curlpp:

#include <curlpp/cURLpp.hpp>#include <curlpp/Easy.hpp>#include <sstream>

int main() {    try {        curlpp::Cleanup cleaner;        curlpp::Easy request;

        // Setting the URL        request.setOpt(new curlpp::options::Url("https://api.example.com/data"));

        // Getting the response into a string stream        std::ostringstream response;        request.setOpt(new curlpp::options::WriteStream(&response));

        // Executing the request        request.perform();

        std::cout << "Response: " << response.str() << std::endl;    }    catch (curlpp::RuntimeError & e) {        std::cerr << "Error: " << e.what() << std::endl;    }    return 0;}

2. C++ REST SDK (cpprestsdk)

C++ REST SDK (formerly known as Casablanca) is an asynchronous library from Microsoft, focused on working with RESTful services. It provides a convenient interface based on pplx::task (an analogue of C++ std::future), which simplifies writing non-blocking code.

Key Features:

• Full asynchrony based on task and continuation.
• Built-in JSON support (cpprest/json.h).
• WebSocket client.
• HTTP/HTTPS support, authorization (Basic, OAuth).
• Cross-platform (Windows, Linux, macOS).

Example of an asynchronous POST request with JSON:

#include <cpprest/http_client.h>#include <cpprest/filestream.h>#include <cpprest/json.h>

using namespace web;using namespace web::http;using namespace web::http::client;

int main() {    http_client client(U("https://api.example.com"));

    // Forming the JSON request body    json::value body;    body[U("name")] = json::value::string(U("John"));    body[U("age")] = json::value::number(30);

    // POST request    client.request(methods::POST, U("/users"), body.serialize(), U("application/json"))        .then([](http_response response) {            if (response.status_code() == status_codes::Created) {                return response.extract_json();            }            throw std::runtime_error("Request error");        })        .then([](json::value answer) {            std::cout << "Response: " << answer.serialize() << std::endl;