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//
// Copyright (c) 2022 Klemens D. Morgenstern (klemens dot morgenstern at gmx dot net)
//
// 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)
//
// Official repository: https://github.com/boostorg/beast
//
//------------------------------------------------------------------------------
//
// Example: HTTP client, coroutine
//
//------------------------------------------------------------------------------
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/awaitable.hpp>
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/use_awaitable.hpp>
#if defined(BOOST_ASIO_HAS_CO_AWAIT)
#include <cstdlib>
#include <functional>
#include <iostream>
#include <string>
namespace beast = boost::beast; // from <boost/beast.hpp>
namespace http = beast::http; // from <boost/beast/http.hpp>
namespace net = boost::asio; // from <boost/asio.hpp>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
//------------------------------------------------------------------------------
// Performs an HTTP GET and prints the response
net::awaitable<void>
do_session(
std::string host,
std::string port,
std::string target,
int version)
{
// These objects perform our I/O
// They use an executor with a default completion token of use_awaitable
// This makes our code easy, but will use exceptions as the default error handling,
// i.e. if the connection drops, we might see an exception.
auto resolver = net::use_awaitable.as_default_on(tcp::resolver(co_await net::this_coro::executor));
auto stream = net::use_awaitable.as_default_on(beast::tcp_stream(co_await net::this_coro::executor));
// Look up the domain name
auto const results = co_await resolver.async_resolve(host, port);
// Set the timeout.
stream.expires_after(std::chrono::seconds(30));
// Make the connection on the IP address we get from a lookup
co_await stream.async_connect(results);
// Set up an HTTP GET request message
http::request<http::string_body> req{http::verb::get, target, version};
req.set(http::field::host, host);
req.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
// Set the timeout.
stream.expires_after(std::chrono::seconds(30));
// Send the HTTP request to the remote host
co_await http::async_write(stream, req);
// This buffer is used for reading and must be persisted
beast::flat_buffer b;
// Declare a container to hold the response
http::response<http::dynamic_body> res;
// Receive the HTTP response
co_await http::async_read(stream, b, res);
// Write the message to standard out
std::cout << res << std::endl;
// Gracefully close the socket
beast::error_code ec;
stream.socket().shutdown(tcp::socket::shutdown_both, ec);
// not_connected happens sometimes
// so don't bother reporting it.
//
if(ec && ec != beast::errc::not_connected)
throw boost::system::system_error(ec, "shutdown");
// If we get here then the connection is closed gracefully
}
//------------------------------------------------------------------------------
int main(int argc, char** argv)
{
// Check command line arguments.
if(argc != 4 && argc != 5)
{
std::cerr <<
"Usage: http-client-awaitable <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" <<
"Example:\n" <<
" http-client-awaitable www.example.com 80 /\n" <<
" http-client-awaitable www.example.com 80 / 1.0\n";
return EXIT_FAILURE;
}
auto const host = argv[1];
auto const port = argv[2];
auto const target = argv[3];
int version = argc == 5 && !std::strcmp("1.0", argv[4]) ? 10 : 11;
// The io_context is required for all I/O
net::io_context ioc;
// Launch the asynchronous operation
net::co_spawn(
ioc,
do_session(host, port, target, version),
// If the awaitable exists with an exception, it gets delivered here as `e`.
// This can happen for regular errors, such as connection drops.
[](std::exception_ptr e)
{
if (e)
try
{
std::rethrow_exception(e);
}
catch(std::exception & ex)
{
std::cerr << "Error: " << ex.what() << "\n";
}
});
// Run the I/O service. The call will return when
// the get operation is complete.
ioc.run();
return EXIT_SUCCESS;
}
#else
int main(int, char * [])
{
std::printf("awaitables require C++20\n");
return 1;
}
#endif
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