Boost asio异步http客户端超时
Boost asio async http client timeout?
在boost asio async http客户端中,如何设置http下载操作的超时?
我检查了这些示例,但它们没有提供带超时的http客户端。
更具体地说,如何修改此示例以支持超时:
#include <iostream>
#include <istream>
#include <ostream>
#include <string>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
using boost::asio::ip::tcp;
class client
{
public:
client(boost::asio::io_service& io_service,
const std::string& server, const std::string& path)
: resolver_(io_service),
socket_(io_service)
{
std::ostream request_stream(&request_);
request_stream << "GET " << path << " HTTP/1.0rn";
request_stream << "Host: " << server << "rn";
request_stream << "Accept: */*rn";
request_stream << "Connection: closernrn";
tcp::resolver::query query(server, "http");
resolver_.async_resolve(query,
boost::bind(&client::handle_resolve, this,
boost::asio::placeholders::error,
boost::asio::placeholders::iterator));
}
private:
void handle_resolve(const boost::system::error_code& err,
tcp::resolver::iterator endpoint_iterator)
{
if (!err)
{
boost::asio::async_connect(socket_, endpoint_iterator,
boost::bind(&client::handle_connect, this,
boost::asio::placeholders::error));
}
else
{
std::cout << "Error: " << err.message() << "n";
}
}
void handle_connect(const boost::system::error_code& err)
{
if (!err)
{
boost::asio::async_write(socket_, request_,
boost::bind(&client::handle_write_request, this,
boost::asio::placeholders::error));
}
else
{
std::cout << "Error: " << err.message() << "n";
}
}
void handle_write_request(const boost::system::error_code& err)
{
if (!err)
{
boost::asio::async_read_until(socket_, response_, "rn",
boost::bind(&client::handle_read_status_line, this,
boost::asio::placeholders::error));
}
else
{
std::cout << "Error: " << err.message() << "n";
}
}
void handle_read_status_line(const boost::system::error_code& err)
{
if (!err)
{
std::istream response_stream(&response_);
std::string http_version;
response_stream >> http_version;
unsigned int status_code;
response_stream >> status_code;
std::string status_message;
std::getline(response_stream, status_message);
if (!response_stream || http_version.substr(0, 5) != "HTTP/")
{
std::cout << "Invalid responsen";
return;
}
if (status_code != 200)
{
std::cout << "Response returned with status code ";
std::cout << status_code << "n";
return;
}
boost::asio::async_read_until(socket_, response_, "rnrn",
boost::bind(&client::handle_read_headers, this,
boost::asio::placeholders::error));
}
else
{
std::cout << "Error: " << err << "n";
}
}
void handle_read_headers(const boost::system::error_code& err)
{
if (!err)
{
std::istream response_stream(&response_);
std::string header;
while (std::getline(response_stream, header) && header != "r")
std::cout << header << "n";
std::cout << "n";
if (response_.size() > 0)
std::cout << &response_;
boost::asio::async_read(socket_, response_,
boost::asio::transfer_at_least(1),
boost::bind(&client::handle_read_content, this,
boost::asio::placeholders::error));
}
else
{
std::cout << "Error: " << err << "n";
}
}
void handle_read_content(const boost::system::error_code& err)
{
if (!err)
{
std::cout << &response_;
boost::asio::async_read(socket_, response_,
boost::asio::transfer_at_least(1),
boost::bind(&client::handle_read_content, this,
boost::asio::placeholders::error));
}
else if (err != boost::asio::error::eof)
{
std::cout << "Error: " << err << "n";
}
}
tcp::resolver resolver_;
tcp::socket socket_;
boost::asio::streambuf request_;
boost::asio::streambuf response_;
};
int http_download(string &server, string &path)
{
try
{
boost::asio::io_service io_service;
client c(io_service, server, path);
io_service.run();
}
catch (std::exception& e)
{
std::cout << "Exception: " << e.what() << "n";
}
return 0;
}
如果您只需要从http_download退出10秒钟(例如(你可以用这种方式:
将deadline_timer添加到类客户端:
boost::asio::deadline_timer timer_;
在构造函数中初始化:
timer_(io_service,boost::posix_time::seconds(10)),
添加计时器的处理程序:
timer_.async_wait(boost::bind(&client::close_connection, this));
在类客户端中创建方法close_connection,您需要关闭插座。可能的构造函数:
client(boost::asio::io_service& io_service,
const std::string& server, const std::string& path)
: resolver_(io_service),
socket_(io_service),
timer_(io_service,boost::posix_time::seconds(10))
{
timer_.async_wait(boost::bind(&client::close_connection, this));
std::ostream request_stream(&request_);
request_stream << "GET " << path << " HTTP/1.0rn";
request_stream << "Host: " << server << "rn";
request_stream << "Accept: */*rn";
request_stream << "Connection: closernrn";
...
}
您可以同时运行一个deadline_timer
,然后在它过期时调用socket.cancel()
,这将导致当前操作中止。然后,如果您愿意,您可以专门处理取消错误代码。
例如,这就是MS的Casablanca代码所采用的方法。
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