libs/beast/example/http/client/async-ssl-system-executor/http_client_async_ssl_system_executor.cpp

   1 //
   2 // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // Official repository: https://github.com/boostorg/beast
   8 //
   9
  10 //------------------------------------------------------------------------------
  11 //
  12 // Example: HTTP SSL client, asynchronous, using system_executor
  13 //
  14 //------------------------------------------------------------------------------
  15
  16 #include "example/common/root_certificates.hpp"
  17
  18 #include <boost/beast/core.hpp>
  19 #include <boost/beast/http.hpp>
  20 #include <boost/beast/ssl.hpp>
  21 #include <boost/beast/version.hpp>
  22 #include <boost/asio/strand.hpp>
  23 #include <boost/asio/system_executor.hpp>
  24 #include <cstdlib>
  25 #include <functional>
  26 #include <iostream>
  27 #include <memory>
  28 #include <string>
  29
  30 namespace beast = boost::beast;         // from <boost/beast.hpp>
  31 namespace http = beast::http;           // from <boost/beast/http.hpp>
  32 namespace net = boost::asio;            // from <boost/asio.hpp>
  33 namespace ssl = boost::asio::ssl;       // from <boost/asio/ssl.hpp>
  34 using tcp = boost::asio::ip::tcp;       // from <boost/asio/ip/tcp.hpp>
  35
  36 //------------------------------------------------------------------------------
  37
  38 // Report a failure
  39 void
  40 fail(beast::error_code ec, char const* what)
  41 {
  42     std::cerr << what << ": " << ec.message() << "\n";
  43 }
  44
  45 // Performs an HTTP GET and prints the response
  46 class session : public std::enable_shared_from_this<session>
  47 {
  48     tcp::resolver resolver_;
  49     beast::ssl_stream<beast::tcp_stream> stream_;
  50     beast::flat_buffer buffer_; // (Must persist between reads)
  51     http::request<http::empty_body> req_;
  52     http::response<http::string_body> res_;
  53
  54     // Objects are constructed with a strand to
  55     // ensure that handlers do not execute concurrently.
  56     session(net::strand<net::system_executor> strand, ssl::context& ctx)
  57         : resolver_(strand)
  58         , stream_(strand, ctx)
  59     {
  60     }
  61
  62 public:
  63     // Delegate construction to a prive constructor to be able to use
  64     // the same strand for both I/O object.
  65     explicit
  66     session(ssl::context& ctx)
  67         : session(net::make_strand(net::system_executor()), ctx)
  68     {
  69     }
  70
  71     // Start the asynchronous operation
  72     void
  73     run(
  74         char const* host,
  75         char const* port,
  76         char const* target,
  77         int version)
  78     {
  79         // Set SNI Hostname (many hosts need this to handshake successfully)
  80         if(! SSL_set_tlsext_host_name(stream_.native_handle(), host))
  81         {
  82             beast::error_code ec{static_cast<int>(::ERR_get_error()), net::error::get_ssl_category()};
  83             std::cerr << ec.message() << "\n";
  84             return;
  85         }
  86
  87         // Set up an HTTP GET request message
  88         req_.version(version);
  89         req_.method(http::verb::get);
  90         req_.target(target);
  91         req_.set(http::field::host, host);
  92         req_.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
  93
  94         // Look up the domain name
  95         resolver_.async_resolve(
  96             host,
  97             port,
  98             beast::bind_front_handler(
  99                 &session::on_resolve,
 100                 shared_from_this()));
 101     }
 102
 103     void
 104     on_resolve(
 105         beast::error_code ec,
 106         tcp::resolver::results_type results)
 107     {
 108         if(ec)
 109             return fail(ec, "resolve");
 110
 111         // Set a timeout on the operation
 112         beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
 113
 114         // Make the connection on the IP address we get from a lookup
 115         beast::get_lowest_layer(stream_).async_connect(
 116             results,
 117             beast::bind_front_handler(
 118                 &session::on_connect,
 119                 shared_from_this()));
 120     }
 121
 122     void
 123     on_connect(beast::error_code ec, tcp::resolver::results_type::endpoint_type)
 124     {
 125         if(ec)
 126             return fail(ec, "connect");
 127
 128         // Perform the SSL handshake
 129         stream_.async_handshake(
 130             ssl::stream_base::client,
 131             beast::bind_front_handler(
 132                 &session::on_handshake,
 133                 shared_from_this()));
 134     }
 135
 136     void
 137     on_handshake(beast::error_code ec)
 138     {
 139         if(ec)
 140             return fail(ec, "handshake");
 141
 142         // Set a timeout on the operation
 143         beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
 144
 145         // Send the HTTP request to the remote host
 146         http::async_write(stream_, req_,
 147             beast::bind_front_handler(
 148                 &session::on_write,
 149                 shared_from_this()));
 150     }
 151
 152     void
 153     on_write(
 154         beast::error_code ec,
 155         std::size_t bytes_transferred)
 156     {
 157         boost::ignore_unused(bytes_transferred);
 158
 159         if(ec)
 160             return fail(ec, "write");
 161
 162         // Receive the HTTP response
 163         http::async_read(stream_, buffer_, res_,
 164             beast::bind_front_handler(
 165                 &session::on_read,
 166                 shared_from_this()));
 167     }
 168
 169     void
 170     on_read(
 171         beast::error_code ec,
 172         std::size_t bytes_transferred)
 173     {
 174         boost::ignore_unused(bytes_transferred);
 175
 176         if(ec)
 177             return fail(ec, "read");
 178
 179         // Write the message to standard out
 180         std::cout << res_ << std::endl;
 181
 182         // Set a timeout on the operation
 183         beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
 184
 185         // Gracefully close the stream
 186         stream_.async_shutdown(
 187             beast::bind_front_handler(
 188                 &session::on_shutdown,
 189                 shared_from_this()));
 190     }
 191
 192     void
 193     on_shutdown(beast::error_code ec)
 194     {
 195         if(ec == net::error::eof)
 196         {
 197             // Rationale:
 198             // http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
 199             ec = {};
 200         }
 201         if(ec)
 202             return fail(ec, "shutdown");
 203
 204         // If we get here then the connection is closed gracefully
 205     }
 206 };
 207
 208 //------------------------------------------------------------------------------
 209
 210 int main(int argc, char** argv)
 211 {
 212     // Check command line arguments.
 213     if(argc != 4 && argc != 5)
 214     {
 215         std::cerr <<
 216             "Usage: http-client-async-ssl-system-executor <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" <<
 217             "Example:\n" <<
 218             "    http-client-async-ssl-system-executor www.example.com 443 /\n" <<
 219             "    http-client-async-ssl-system-executor www.example.com 443 / 1.0\n";
 220         return EXIT_FAILURE;
 221     }
 222     auto const host = argv[1];
 223     auto const port = argv[2];
 224     auto const target = argv[3];
 225     int version = argc == 5 && !std::strcmp("1.0", argv[4]) ? 10 : 11;
 226
 227     // The SSL context is required, and holds certificates
 228     ssl::context ctx{ssl::context::tlsv12_client};
 229
 230     // This holds the root certificate used for verification
 231     load_root_certificates(ctx);
 232
 233     // Verify the remote server's certificate
 234     ctx.set_verify_mode(ssl::verify_peer);
 235
 236     // Launch the asynchronous operation
 237     std::make_shared<session>(ctx)->run(host, port, target, version);
 238
 239
 240     // The async operations will run on the system_executor.
 241     // Because the main thread has nothing to do in this example, we just wait
 242     // for the system_executor to run out of work.
 243     net::system_executor().context().join();
 244
 245     return EXIT_SUCCESS;
 246 }