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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/ssl.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/as_tuple.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>
#include "example/common/root_certificates.hpp"
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>
namespace ssl = boost::asio::ssl; // from <boost/asio/ssl.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,
ssl::context& ctx)
{
// 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.
// See async_shutdown for error handling with an error_code.
auto resolver = net::use_awaitable.as_default_on(tcp::resolver(co_await net::this_coro::executor));
using executor_with_default = net::use_awaitable_t<>::executor_with_default<net::any_io_executor>;
using tcp_stream = typename beast::tcp_stream::rebind_executor<executor_with_default>::other;
// We construct the ssl stream from the already rebound tcp_stream.
beast::ssl_stream<tcp_stream> stream{
net::use_awaitable.as_default_on(beast::tcp_stream(co_await net::this_coro::executor)),
ctx};
// Set SNI Hostname (many hosts need this to handshake successfully)
if(! SSL_set_tlsext_host_name(stream.native_handle(), host.c_str()))
throw boost::system::system_error(static_cast<int>(::ERR_get_error()), net::error::get_ssl_category());
// Look up the domain name
auto const results = co_await resolver.async_resolve(host, port);
// Set the timeout.
beast::get_lowest_layer(stream).expires_after(std::chrono::seconds(30));
// Make the connection on the IP address we get from a lookup
co_await beast::get_lowest_layer(stream).async_connect(results);
// Set the timeout.
beast::get_lowest_layer(stream).expires_after(std::chrono::seconds(30));
// Perform the SSL handshake
co_await stream.async_handshake(ssl::stream_base::client);
// 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.
beast::get_lowest_layer(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;
// Set the timeout.
beast::get_lowest_layer(stream).expires_after(std::chrono::seconds(30));
// Gracefully close the stream - do not threat every error as an exception!
auto [ec] = co_await stream.async_shutdown(net::as_tuple(net::use_awaitable));
if (ec == net::error::eof)
{
// Rationale:
// http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
ec = {};
}
if (ec)
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 443 /\n" <<
" http-client-awaitable www.example.com 443 / 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;
// The SSL context is required, and holds certificates
ssl::context ctx{ssl::context::tlsv12_client};
// This holds the root certificate used for verification
load_root_certificates(ctx);
// Verify the remote server's certificate
ctx.set_verify_mode(ssl::verify_peer);
// Launch the asynchronous operation
net::co_spawn(
ioc,
do_session(host, port, target, version, ctx),
// 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)
return ;
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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