HTTP and WebSocket built on Boost.Asio in C++11

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Appearances

CppCast 2017	CppCon 2016

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Contents

• Introduction
• Description
• Requirements
• Building
• Usage
• Licence
• Contact

Introduction

Beast is a header-only, cross-platform C++ library built on Boost.Asio and Boost, containing two modules implementing widely used network protocols. Beast.HTTP offers a universal model for describing, sending, and receiving HTTP messages while Beast.WebSocket provides a complete implementation of the WebSocket protocol. Their design achieves these goals:

• Symmetry. Interfaces are role-agnostic; the same interfaces can be used to build clients, servers, or both.

• Ease of Use. HTTP messages are modeled using simple, readily accessible objects. Functions and classes used to send and receive HTTP or WebSocket messages are designed to resemble Boost.Asio as closely as possible. Users familiar with Boost.Asio will be immediately comfortable using this library.

• Flexibility. Interfaces do not mandate specific implementation strategies; important decisions such as buffer or thread management are left to users of the library.

• Performance. The implementation performs competitively, making it a realistic choice for building high performance network servers.

• Scalability. Development of network applications that scale to thousands of concurrent connections is possible with the implementation.

• Basis for further abstraction. The interfaces facilitate the development of other libraries that provide higher levels of abstraction.

Beast is used in rippled, an open source server application that implements a decentralized cryptocurrency system.

Description

This software is currently in beta: interfaces may change. For recent changes see the CHANGELOG. The library has been submitted to the Boost Library Incubator

• Project Site
• Repository
• Project Documentation
• Autobahn.testsuite results

Requirements

• Boost 1.58 or later
• C++11 or later

When using Microsoft Visual C++, Visual Studio 2015 Update 3 or later is required.

These components are optionally required in order to build the tests and examples:

• OpenSSL (optional)
• CMake 3.7.2 or later (optional)
• Properly configured bjam/b2 (optional)

Building

Beast is header-only so there are no libraries to build or link with. To use Beast in your project, simply copy the Beast sources to your project's source tree (alternatively, bring Beast into your Git repository using the git subtree or git submodule commands). Then, edit your build scripts to add the include/ directory to the list of paths checked by the C++ compiler when searching for includes. Beast #include lines will look like this:

#include <beast/http.hpp>
#include <beast/websocket.hpp>

To link your program successfully, you'll need to add the Boost.System library to link with. If you use coroutines you'll also need the Boost.Coroutine library. Please visit the Boost documentation for instructions on how to do this for your particular build system.

For the examples and tests, Beast provides build scripts for Boost.Build (bjam) and CMake. It is possible to generate Microsoft Visual Studio or Apple Developers using Microsoft Visual Studio can generate Visual Studio project files by executing these commands from the root of the repository:

cd bin
cmake ..                                    # for 32-bit Windows builds

cd ../bin64
cmake ..                                    # for Linux/Mac builds, OR
cmake -G"Visual Studio 14 2015 Win64" ..    # for 64-bit Windows builds

When using Apple Xcode it is possible to generate Xcode project files using these commands:

cd bin
cmake -G Xcode ..                           # for Apple Xcode builds

To build with Boost.Build, it is necessary to have the bjam executable in your path. And bjam needs to know how to find the Boost sources. The easiest way to do this is make sure that the version of bjam in your path is the one at the root of the Boost source tree, which is built when running bootstrap.sh (or bootstrap.bat on Windows).

Once bjam is in your path, simply run bjam in the root of the Beast repository to automatically build the required Boost libraries if they are not already built, build the examples, then build and run the unit tests.

The files in the repository are laid out thusly:

./
    bin/            Holds executables and project files
    bin64/          Holds 64-bit Windows executables and project files
    doc/            Source code and scripts for the documentation
    include/        Add this to your compiler includes
        beast/
    extras/         Additional APIs, may change
    examples/       Self contained example programs
    test/           Unit tests and benchmarks

Usage

These examples are complete, self-contained programs that you can build and run yourself (they are in the examples directory).

Example WebSocket program:

#include <beast/core/to_string.hpp>
#include <beast/websocket.hpp>
#include <boost/asio.hpp>
#include <iostream>
#include <string>

int main()
{
    // Normal boost::asio setup
    std::string const host = "echo.websocket.org";
    boost::asio::io_service ios;
    boost::asio::ip::tcp::resolver r{ios};
    boost::asio::ip::tcp::socket sock{ios};
    boost::asio::connect(sock,
        r.resolve(boost::asio::ip::tcp::resolver::query{host, "80"}));

    // WebSocket connect and send message using beast
    beast::websocket::stream<boost::asio::ip::tcp::socket&> ws{sock};
    ws.handshake(host, "/");
    ws.write(boost::asio::buffer(std::string("Hello, world!")));

    // Receive WebSocket message, print and close using beast
    beast::streambuf sb;
    beast::websocket::opcode op;
    ws.read(op, sb);
    ws.close(beast::websocket::close_code::normal);
    std::cout << beast::to_string(sb.data()) << "\n";
}

Example HTTP program:

#include <beast/http.hpp>
#include <boost/asio.hpp>
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <string>

int main()
{
    // Normal boost::asio setup
    std::string const host = "boost.org";
    boost::asio::io_service ios;
    boost::asio::ip::tcp::resolver r{ios};
    boost::asio::ip::tcp::socket sock{ios};
    boost::asio::connect(sock,
        r.resolve(boost::asio::ip::tcp::resolver::query{host, "http"}));

    // Send HTTP request using beast
    beast::http::request<beast::http::empty_body> req;
    req.method = "GET";
    req.url = "/";
    req.version = 11;
    req.fields.replace("Host", host + ":" +
        boost::lexical_cast<std::string>(sock.remote_endpoint().port()));
    req.fields.replace("User-Agent", "Beast");
    beast::http::prepare(req);
    beast::http::write(sock, req);

    // Receive and print HTTP response using beast
    beast::streambuf sb;
    beast::http::response<beast::http::streambuf_body> resp;
    beast::http::read(sock, sb, resp);
    std::cout << resp;
}

License

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Contact

Please report issues or questions here: https://github.com/vinniefalco/Beast/issues