...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Use HTTP to make a GET request to a website and print the response:
File: http_sync_client.cpp
#include <boost/beast/core.hpp> #include <boost/beast/http.hpp> #include <boost/beast/version.hpp> #include <boost/asio/connect.hpp> #include <boost/asio/ip/tcp.hpp> #include <cstdlib> #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 = net::ip::tcp; // from <boost/asio/ip/tcp.hpp> // Performs an HTTP GET and prints the response int main(int argc, char** argv) { try { // Check command line arguments. if(argc != 4 && argc != 5) { std::cerr << "Usage: http-client-sync <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" << "Example:\n" << " http-client-sync www.example.com 80 /\n" << " http-client-sync 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; // These objects perform our I/O tcp::resolver resolver(ioc); beast::tcp_stream stream(ioc); // Look up the domain name auto const results = resolver.resolve(host, port); // Make the connection on the IP address we get from a lookup stream.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); // Send the HTTP request to the remote host http::write(stream, req); // This buffer is used for reading and must be persisted beast::flat_buffer buffer; // Declare a container to hold the response http::response<http::dynamic_body> res; // Receive the HTTP response http::read(stream, buffer, 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 beast::system_error{ec}; // If we get here then the connection is closed gracefully } catch(std::exception const& e) { std::cerr << "Error: " << e.what() << std::endl; return EXIT_FAILURE; } return EXIT_SUCCESS; }