Boost :: Asio同步客户端超时 [英] Boost::Asio synchronous client with timeout
本文介绍了Boost :: Asio同步客户端超时的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在尝试使用线程作为超时控件来构建具有超时的同步FTP客户端代码.该线程将在每个事务上启动，并在超时的情况下关闭套接字-这将迫使同步调用返回错误.
I´m trying to build a synchronous FTP client code with timeout using a thread as the timeout control. The thread will be started on every transaction and will close the socket in case of timeout - that will force the syncronous call to return with error.
这是我的代码:
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <thread>
#include <chrono>
#include <boost/asio.hpp>
#define TIMEOUT_SECONDS 5
#define MAX_MESSAGE_SIZE 4096
using boost::asio::ip::tcp;
enum { max_length = 1024 };
bool timerOn;
void socket_timer(tcp::socket& s, int seconds)
{
std::chrono::system_clock::time_point start = std::chrono::system_clock::now();
while (timerOn)
{
std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
auto interval = std::chrono::duration_cast<std::chrono::seconds>(now - start).count();
if (interval > seconds)
break;
std::this_thread::sleep_for(std::chrono::milliseconds(10)); // Not to run in 100% CPU
}
if (timerOn)
s.close();
}
void start_timer(int seconds, tcp::socket& s)
{
timerOn = true;
std::thread t(socket_timer, s, seconds);
t.detach();
}
void stop_timer()
{
timerOn = false;
}
int main(int argc, char* argv[])
{
std::string address;
while(address != "END")
{
try
{
boost::asio::io_service io_service;
std::cout << "Enter FTP server address to connect or END to finish: " << std::endl;
std::cin >> address;
if (address == "END")
break;
tcp::socket s(io_service);
tcp::resolver resolver(io_service);
boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::address::from_string(address), 21);
start_timer(TIMEOUT_SECONDS, s);
boost::system::error_code ec;
s.connect(endpoint, ec);
stop_timer();
if (ec)
{
throw std::runtime_error("Error connecting to server.");
}
std::cout << "Connected to " << s.remote_endpoint().address().to_string() << std::endl;
char reply[max_length];
start_timer(TIMEOUT_SECONDS, s);
size_t bytes = s.receive(boost::asio::buffer(reply, MAX_MESSAGE_SIZE), 0, ec);
stop_timer();
if (ec)
{
throw std::runtime_error("Error receiving message.");
}
std::cout << "Received message is: ";
std::cout.write(reply, bytes);
std::cout << "\n";
std::cout << "Enter message: ";
char request[max_length];
std::cin.getline(request, max_length);
size_t request_length = std::strlen(request);
start_timer(TIMEOUT_SECONDS, s);
boost::asio::write(s, boost::asio::buffer(request, request_length));
stop_timer();
if (ec)
{
throw std::runtime_error("Error sending message.");
}
}
catch (std::exception& e)
{
std::cerr << "COMMUNICATIONS ERROR." << "\n";
std::cerr << "Exception: " << e.what() << "\n";
}
}
return 0;
}
我无法编译这段代码，因为boost向我显示了以下错误:
I simply cannot compile this code, as boost is showing me the following error:
1>------ Build started: Project: TestAsio, Configuration: Debug Win32 ------
1> main.cpp
1>c:\boost_1_60\boost\asio\basic_socket.hpp(1513): error C2248: 'boost::asio::basic_io_object<IoObjectService>::basic_io_object' : cannot access private member declared in class 'boost::asio::basic_io_object<IoObjectService>'
1> with
1> [
1> IoObjectService=boost::asio::stream_socket_service<boost::asio::ip::tcp>
1> ]
1> c:\boost_1_60\boost\asio\basic_io_object.hpp(230) : see declaration of 'boost::asio::basic_io_object<IoObjectService>::basic_io_object'
1> with
1> [
1> IoObjectService=boost::asio::stream_socket_service<boost::asio::ip::tcp>
1> ]
1> This diagnostic occurred in the compiler generated function 'boost::asio::basic_socket<Protocol,SocketService>::basic_socket(const boost::asio::basic_socket<Protocol,SocketService> &)'
1> with
1> [
1> Protocol=boost::asio::ip::tcp,
1> SocketService=boost::asio::stream_socket_service<boost::asio::ip::tcp>
1> ]
========== Build: 0 succeeded, 1 failed, 9 up-to-date, 0 skipped ==========
所以，我想了解两件事:
So, I wanna know about 2 things:
a)我在代码中做错什么了吗?
a) What am I doing wrong in the code ?
b)这种关闭并行线程上的套接字的方法是否可以使套接字超时?请随意发表评论.
b) Will this approach of closing the socket on a parallel thread work for timing out the socket ? Please fell free to comment it.
感谢您的帮助.
推荐答案
我已经建立了一个辅助工具，可以在此处超时的情况下同步"执行任何Asio异步操作，请查找await_operation:
I've made a helper facility to do any Asio async operation "synchronously" with a timeout here, look for await_operation:
您应该能够调整样本的模式.
You should be able to adapt the pattern for your sample.
花了一段时间，因为我想用ftp服务器进行测试.
It took a while since I wanted to test this with an ftp server.
注意:
- 您没有解析地址(实际上要求用户输入IP地址)
- 您不确定命令是否已用换行符关闭
- 您没有处理任何输入错误
使用我的await_operation修复这些问题和，您将获得以下信息:
Fixing these things and using my await_operation you'd get this:
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <thread>
#include <chrono>
#include <boost/asio.hpp>
#include <boost/asio/high_resolution_timer.hpp>
#define TIMEOUT std::chrono::seconds(5)
#define MAX_MESSAGE_SIZE 4096
using boost::asio::ip::tcp;
enum { max_length = 2048 };
struct Service {
using error_code = boost::system::error_code;
template<typename AllowTime, typename Cancel> void await_operation_ex(AllowTime const& deadline_or_duration, Cancel&& cancel) {
using namespace boost::asio;
ioservice.reset();
{
high_resolution_timer tm(ioservice, deadline_or_duration);
tm.async_wait([&cancel](error_code ec) { if (ec != error::operation_aborted) std::forward<Cancel>(cancel)(); });
ioservice.run_one();
}
ioservice.run();
}
template<typename AllowTime, typename ServiceObject> void await_operation(AllowTime const& deadline_or_duration, ServiceObject& so) {
return await_operation_ex(deadline_or_duration, [&so]{ so.cancel(); });
}
boost::asio::io_service ioservice;
};
int main()
{
while(true)
{
try
{
Service service;
std::cout << "Enter FTP server address to connect or END to finish: " << std::endl;
std::string address;
if (std::cin >> address) {
if (address == "END") break;
} else {
if (std::cin.eof())
break;
std::cerr << "Invalid input ignored\n";
std::cin.clear();
std::cin.ignore(1024, '\n');
continue;
}
tcp::socket s(service.ioservice);
tcp::resolver resolver(service.ioservice);
boost::asio::async_connect(s, resolver.resolve({address, "21"}), [](boost::system::error_code ec, tcp::resolver::iterator it) {
if (ec) throw std::runtime_error("Error connecting to server: " + ec.message());
std::cout << "Connected to " << it->endpoint() << std::endl;
});
service.await_operation_ex(TIMEOUT, [&]{
throw std::runtime_error("Error connecting to server: timeout\n");
});
auto receive = [&] {
boost::asio::streambuf sb;
size_t bytes;
boost::asio::async_read_until(s, sb, '\n', [&](boost::system::error_code ec, size_t bytes_transferred) {
if (ec) throw std::runtime_error("Error receiving message: " + ec.message());
bytes = bytes_transferred;
std::cout << "Received message is: " << &sb;
});
service.await_operation(TIMEOUT, s);
return bytes;
};
receive(); // banner
auto send = [&](std::string cmd) {
boost::asio::async_write(s, boost::asio::buffer(cmd), [](boost::system::error_code ec, size_t /*bytes_transferred*/) {
if (ec) throw std::runtime_error("Error sending message: " + ec.message());
});
service.await_operation(TIMEOUT, s);
};
auto ftp_command = [&](std::string cmd) {
send(cmd + "\r\n");
receive(); // response
};
//ftp_command("USER bob");
//ftp_command("PASS hello");
while (true) {
std::cout << "Enter command: ";
std::string request;
if (!std::getline(std::cin, request))
break;
ftp_command(request);
}
}
catch (std::exception const& e)
{
std::cerr << "COMMUNICATIONS ERROR " << e.what() << "\n";
}
}
return 0;
}
在我的测试运行中，打印例如:
Which, in my test run, prints e.g.:
这篇关于Boost :: Asio同步客户端超时的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
