code: https://gist.github.com/Naseefabu/173c928603e564879683ccdf10d9d0f8
当我运行此命令并将响应打印到控制台时:
Sending GET /api/v3/time HTTP/1.1
Host: api.binance.com
content-type: application/json
User-Agent: Boost.Beast/330
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
Content-Length: 28
Connection: keep-alive
Date: Fri, 13 May 2022 17:18:47 GMT
Server: nginx
x-mbx-uuid: 7e7465db-011a-4308-aa1e-6603d72c8c9a
x-mbx-used-weight: 1
x-mbx-used-weight-1m: 1
Strict-Transport-Security: max-age=31536000; includeSubdomains
X-Frame-Options: SAMEORIGIN
X-Xss-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Security-Policy: default-src 'self'
X-Content-Security-Policy: default-src 'self'
X-WebKit-CSP: default-src 'self'
Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, HEAD, OPTIONS
X-Cache: Miss from cloudfront
Via: 1.1 dfccb338f8c0489ab09835ea7dbad1a8.cloudfront.net (CloudFront)
X-Amz-Cf-Pop: MAA51-P1
X-Amz-Cf-Id: waTqtDHSDpk74QB7zkF5Ya0CdRVWuJuC-M4TZqSuMd2bfXawkq6o6g==
{"serverTime":1652462327804}
shutdown: stream truncated
如果我只想得到json响应:{"serverTime":1652462327804}怎么办?并存储在json变量，所以我可以使用它为我的需要，其他信息对我来说不是那么重要，提前谢谢!
binapi::AsyncRest::httpClient* client;
这是非常可疑的，因为该类正在使用enable_shared_from_this()。很确定应该是
auto client =
std::make_shared<binapi::AsyncRest::httpClient>(ioc.get_executor(), ctx);
接下来，我假设get_server_time是一个静态函数。我不明白为什么它是httpClient的成员。
所以添加所有缺失的代码回来(使用大量的经验):
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>
#include <boost/beast.hpp>
#include <boost/beast/ssl.hpp>
#include <boost/url.hpp>
#include <boost/url/src.hpp> // for header-only
#include <fstream>
#include <iomanip>
#include <iostream>
namespace net = boost::asio;
namespace beast = boost::beast;
namespace http = boost::beast::http;
namespace ssl = boost::asio::ssl;
using net::ip::tcp;
namespace binapi { namespace AsyncRest {
// Report a failure
void fail_http(beast::error_code ec, char const* what) {
std::cerr << what << ": " << ec.message() << "n";
}
struct httpClient : std::enable_shared_from_this<httpClient> {
using executor = net::any_io_executor;
using Stream = beast::ssl_stream<beast::tcp_stream>;
tcp::resolver resolver_;
Stream stream_;
beast::flat_buffer buffer_;
http::request<http::empty_body> req_;
http::response<http::string_body> res_;
httpClient(executor ex, ssl::context& ctx);
// Start the asynchronous operation
void run(boost::url, http::verb);
void on_resolve(beast::error_code, tcp::resolver::results_type);
void on_connect(beast::error_code, tcp::resolver::results_type::endpoint_type);
void on_handshake(beast::error_code);
void on_write(beast::error_code, size_t bytes_transferred);
void on_read(beast::error_code, size_t bytes_transferred);
void on_shutdown(beast::error_code);
};
httpClient::httpClient(executor ex, ssl::context& ctx)
: resolver_(ex)
, stream_(ex, ctx) {}
// Start the asynchronous operation
void httpClient::run(boost::url url, http::verb action) {
std::string const host(url.host());
std::string const service = url.has_port() //
? url.port()
: (url.scheme_id() == boost::urls::scheme::https) //
? "https"
: "http";
url.remove_origin(); // becomes req_.target()
// Set SNI Hostname (many hosts need this to handshake
// successfully)
if (!SSL_set_tlsext_host_name(stream_.native_handle(), host.c_str())) {
beast::error_code ec{static_cast<int>(::ERR_get_error()),
net::error::get_ssl_category()};
std::cerr << ec.message() << "n";
return;
}
// Set up an HTTP GET/POST/DELETE/PUT request message
// req_.version(version);
req_.method(action);
req_.target(url.c_str());
req_.set(http::field::host, host);
req_.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
req_.prepare_payload(); // make HTTP 1.1 compliant
// Look up the domain name
resolver_.async_resolve(
host, service,
beast::bind_front_handler(&httpClient::on_resolve, shared_from_this()));
}
void httpClient::on_resolve(beast::error_code ec,
tcp::resolver::results_type results) {
if (ec)
return fail_http(ec, "resolve");
// Set a timeout on the operation
beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
// Make the connection on the IP address we get from a lookup
beast::get_lowest_layer(stream_).async_connect(
results,
beast::bind_front_handler(&httpClient::on_connect, shared_from_this()));
}
void httpClient::on_connect(beast::error_code ec,
tcp::resolver::results_type::endpoint_type) {
if (ec)
return fail_http(ec, "connect");
// Perform the SSL handshake
stream_.async_handshake(
ssl::stream_base::client,
beast::bind_front_handler(&httpClient::on_handshake, shared_from_this()));
}
void httpClient::on_handshake(beast::error_code ec) {
if (ec)
return fail_http(ec, "handshake");
// Set a timeout on the operation
beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
// Send the HTTP request to the remote host
std::cout << "Sending " << req_ << std::endl;
http::async_write(
stream_, req_,
beast::bind_front_handler(&httpClient::on_write, shared_from_this()));
}
void httpClient::on_write(beast::error_code ec, size_t bytes_transferred) {
boost::ignore_unused(bytes_transferred);
if (ec)
return fail_http(ec, "write");
// Receive the HTTP response
http::async_read(
stream_, buffer_, res_,
beast::bind_front_handler(&httpClient::on_read, shared_from_this()));
}
void httpClient::on_read(beast::error_code ec, size_t bytes_transferred) {
boost::ignore_unused(bytes_transferred);
if (ec)
return fail_http(ec, "read");
// Write the message to standard out
std::cout << res_ << std::endl;
// Set a timeout on the operation
beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));
// Gracefully close the stream
stream_.async_shutdown(
beast::bind_front_handler(&httpClient::on_shutdown, shared_from_this()));
}
void httpClient::on_shutdown(beast::error_code ec) {
if (ec == net::error::eof) {
ec = {};
}
if (ec)
return fail_http(ec, "shutdown");
}
static void get_server_time(net::io_context& ioc, ssl::context& ctx) {
static boost::url_view const uri{"https://api.binance.com/api/v3/time"};
std::make_shared<httpClient>(net::make_strand(ioc), ctx)
->run(uri, http::verb::get);
}
}} // namespace binapi::AsyncRest
int main() {
net::io_context ioc;
// The SSL context is required, and holds certificates
ssl::context ctx{ssl::context::tlsv12_client};
// Verify the remote server's certificate
ctx.set_verify_mode(ssl::verify_peer);
ctx.set_default_verify_paths();
binapi::AsyncRest::get_server_time(ioc, ctx);
ioc.run();
}
现在我们知道res_是beast::http::response<beast::http::string_body>。所以，如果你只想打印正文，打印出来:
std::cout << res_.body() << std::endl;
打印
Sending GET /api/v3/time HTTP/1.1
Host: api.binance.com
User-Agent: Boost.Beast/330
{"serverTime":1652476115413}
shutdown: stream truncated
只打印时间:
static constexpr boost::gregorian::date s_epoch{1970, 1, 1};
auto epoch_seconds = json::parse(res_.body()).at("serverTime").as_int64();
ptime serverTime(s_epoch, boost::posix_time::milliseconds(epoch_seconds));
std::cout << serverTime << std::endl;
打印
2022-May-13 21:38:55.982000
/笔记总结
你真正想要的是像
这样的函数ptime server_time();
或
void async_server_time(auto completionToken);
并且您可能希望共享客户端类实例，而不是每次调用都重新连接。