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 client, coroutine
13//
14//------------------------------------------------------------------------------
15
16#include <boost/beast/core.hpp>
17#include <boost/beast/http.hpp>
18#include <boost/beast/version.hpp>
19#include <boost/asio/spawn.hpp>
20#include <cstdlib>
21#include <functional>
22#include <iostream>
23#include <string>
24
25namespace beast = boost::beast; // from <boost/beast.hpp>
26namespace http = beast::http; // from <boost/beast/http.hpp>
27namespace net = boost::asio; // from <boost/asio.hpp>
28using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
29
30//------------------------------------------------------------------------------
31
32// Report a failure
33void
34fail(beast::error_code ec, char const* what)
35{
36 std::cerr << what << ": " << ec.message() << "\n";
37}
38
39// Performs an HTTP GET and prints the response
40void
41do_session(
42 std::string const& host,
43 std::string const& port,
44 std::string const& target,
45 int version,
46 net::io_context& ioc,
47 net::yield_context yield)
48{
49 beast::error_code ec;
50
51 // These objects perform our I/O
52 tcp::resolver resolver(ioc);
53 beast::tcp_stream stream(ioc);
54
55 // Look up the domain name
56 auto const results = resolver.async_resolve(host, service: port, token: yield[ec]);
57 if(ec)
58 return fail(ec, what: "resolve");
59
60 // Set the timeout.
61 stream.expires_after(expiry_time: std::chrono::seconds(30));
62
63 // Make the connection on the IP address we get from a lookup
64 stream.async_connect(endpoints: results, handler: yield[ec]);
65 if(ec)
66 return fail(ec, what: "connect");
67
68 // Set up an HTTP GET request message
69 http::request<http::string_body> req{http::verb::get, target, version};
70 req.set(name: http::field::host, value: host);
71 req.set(name: http::field::user_agent, BOOST_BEAST_VERSION_STRING);
72
73 // Set the timeout.
74 stream.expires_after(expiry_time: std::chrono::seconds(30));
75
76 // Send the HTTP request to the remote host
77 http::async_write(stream, msg: req, handler: yield[ec]);
78 if(ec)
79 return fail(ec, what: "write");
80
81 // This buffer is used for reading and must be persisted
82 beast::flat_buffer b;
83
84 // Declare a container to hold the response
85 http::response<http::dynamic_body> res;
86
87 // Receive the HTTP response
88 http::async_read(stream, buffer&: b, msg&: res, handler: yield[ec]);
89 if(ec)
90 return fail(ec, what: "read");
91
92 // Write the message to standard out
93 std::cout << res << std::endl;
94
95 // Gracefully close the socket
96 stream.socket().shutdown(what: tcp::socket::shutdown_both, ec);
97
98 // not_connected happens sometimes
99 // so don't bother reporting it.
100 //
101 if(ec && ec != beast::errc::not_connected)
102 return fail(ec, what: "shutdown");
103
104 // If we get here then the connection is closed gracefully
105}
106
107//------------------------------------------------------------------------------
108
109int main(int argc, char** argv)
110{
111 // Check command line arguments.
112 if(argc != 4 && argc != 5)
113 {
114 std::cerr <<
115 "Usage: http-client-coro <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" <<
116 "Example:\n" <<
117 " http-client-coro www.example.com 80 /\n" <<
118 " http-client-coro www.example.com 80 / 1.0\n";
119 return EXIT_FAILURE;
120 }
121 auto const host = argv[1];
122 auto const port = argv[2];
123 auto const target = argv[3];
124 int version = argc == 5 && !std::strcmp(s1: "1.0", s2: argv[4]) ? 10 : 11;
125
126 // The io_context is required for all I/O
127 net::io_context ioc;
128
129 // Launch the asynchronous operation
130 boost::asio::spawn(ctx&: ioc, function: std::bind(
131 f: &do_session,
132 args: std::string(host),
133 args: std::string(port),
134 args: std::string(target),
135 args&: version,
136 args: std::ref(t&: ioc),
137 args: std::placeholders::_1),
138 // on completion, spawn will call this function
139 token: [](std::exception_ptr ex)
140 {
141 // if an exception occurred in the coroutine,
142 // it's something critical, e.g. out of memory
143 // we capture normal errors in the ec
144 // so we just rethrow the exception here,
145 // which will cause `ioc.run()` to throw
146 if (ex)
147 std::rethrow_exception(ex);
148 });
149
150 // Run the I/O service. The call will return when
151 // the get operation is complete.
152 ioc.run();
153
154 return EXIT_SUCCESS;
155}
156

source code of boost/libs/beast/example/http/client/coro/http_client_coro.cpp