RESTinio is a C++17 library that gives you an embedded HTTP/Websocket server. It is based on standalone version of ASIO and targeted primarily for asynchronous processing of HTTP-requests. Boost::ASIO is also supported.

RESTinio itself is a header-only library, but it depends on nodejs/llhttp that is not header-only.

Currently RESTinio is in rather stable state and we think that since v.0.4.0 it is ready for production use.

Consider the task of writing a C++ application that must support some REST API, RESTinio represents our solution for that task.

Lets see how it feels like in the simplest case:

#include <restinio/core.hpp>
int main()
{
    restinio::run(
        restinio::on_this_thread()
        .port(8080)
        .address("localhost")
        .request_handler([](auto req) {
            return req->create_response().set_body("Hello, World!").done();
        }));
    return 0;
}

Server runs on the main thread, and respond to all requests with hello-world message. Of course you've got an access to the structure of a given HTTP request, so you can apply a complex logic for handling requests.

• Async request handling. Cannot get the response data immediately? That's ok, store request handle somewhere and/or pass it to another execution context and get back to it when the data is ready.
• HTTP pipelining. Works well with async request handling. It might increase your server throughput dramatically.
• Timeout control. RESTinio can take care of bad connection that are like: send "GET /" and then just stuck.
• Response builders. Need chunked-encoded body - then RESTinio has a special response builder for you (obviously it is not the only builder).
• ExpressJS-like request routing (see an example below).
• An experimental typesafe request router that allows avoiding problems of ExpressJS-like router with help of static checks from C++ compiler.
• A possibility to chain several request-handlers (somewhat similar to ExpressJS's middleware).
• Working with query string parameters.
• Several ready-to-use helpers for working with HTTP headers (for example, the support for HTTP headers related to file uploading).
• Supports sending files and its parts (with sendfile on linux/unix and TransmitFile on windows).
• Supports compression (deflate, gzip).
• Supports TLS (HTTPS).
• Basic websocket support. Simply restinio::websocket::basic::upgrade() the request handle and start websocket session on a corresponding connection.
• Can run on external asio::io_context. RESTinio is separated from execution context.
• Some tune options. One can set acceptor and socket options. When running RESTinio on a pool of threads connections can be accepted in parallel.

#include <restinio/core.hpp>

using namespace restinio;

template<typename T>
std::ostream & operator<<(std::ostream & to, const optional_t<T> & v) {
    if(v) to << *v;
    return to;
}

int main() {
    // Create express router for our service.
    auto router = std::make_unique<router::express_router_t<>>();
    router->http_get(
            R"(/data/meter/:meter_id(\d+))",
            [](auto req, auto params) {
                const auto qp = parse_query(req->header().query());
                return req->create_response()
                        .set_body(
                                fmt::format("meter_id={} (year={}/mon={}/day={})",
                                        cast_to<int>(params["meter_id"]),
                                        opt_value<int>(qp, "year"),
                                        opt_value<int>(qp, "mon"),
                                        opt_value<int>(qp, "day")))
                        .done();
            });

    router->non_matched_request_handler(
            [](auto req){
                return req->create_response(restinio::status_not_found()).connection_close().done();
            });

    // Launching a server with custom traits.
    struct my_server_traits : public default_single_thread_traits_t {
        using request_handler_t = restinio::router::express_router_t<>;
    };

    restinio::run(
            restinio::on_this_thread<my_server_traits>()
                    .address("localhost")
                    .request_handler(std::move(router)));

    return 0;
}

RESTinio is distributed under BSD-3-CLAUSE license.

The full documentation for RESTinio can be found here.

• Issues and bugs: Issue Tracker on GitHub.
• Discussion section on GitHub.
• Discussion group: restinio.