ASIO - 如何停止基于简单协程的服务器?

Question

我有以下基于协程的简单服务器：

class Server
{
private:
boost::asio::io_service        Service;
boost::asio::ip::tcp::acceptor Acceptor;
boost::asio::ip::tcp::socket   Socket;
private:
void Accept(boost::asio::yield_context Yield);
void Write(boost::asio::yield_context Yield);
public:
Server(): Acceptor(Service), Socket(Service) {}
void Open(unsigned short PortNum);
void Run();
void Stop();
};
void Server::Accept(boost::asio::yield_context Yield)
{
boost::system::error_code ec;
for (;;)
{
Socket.close();
Acceptor.async_accept(Socket,Yield[ec]);
spawn(Yield,std::bind(&Server::Write,this,Yield[ec]));
}
}
void Server::Write(boost::asio::yield_context Yield)
{
char InBuffer[1024]= {};
std::size_t Size;
boost::system::error_code ec;
double Data= 6.66;
for (;;)
{
boost::asio::streambuf OutBuffer;
std::ostream os(&OutBuffer);
Size= Socket.async_read_some(boost::asio::buffer(InBuffer),Yield[ec]);
if (ec)
break;
os.write(reinterpret_cast<const char *>(&Data),sizeof(double));
Socket.async_write_some(OutBuffer.data(),Yield[ec]);
if (ec)
break;
}
}
void Server::Open(unsigned short PortNum)
{
Acceptor.open(boost::asio::ip::tcp::v4());
Acceptor.bind({{},PortNum});
Acceptor.listen();
}
void Server::Run()
{
spawn(Service,std::bind(&Server::Accept,this,std::placeholders::_1));
Service.run();
}
void Server::Stop()
{
Service.stop();
}

我想在线程上运行此服务器，并在主程序即将完成时干净地停止它：

int main()
{
Server s;
s.Open(1024);
std::thread Thread(&Server::Run,&s);
Sleep(10'000);
s.Stop();
Thread.join();
}

不幸的是，如果有一个连接的套接字，当我调用Stop时会抛出异常boost::coroutines::detail::forced_unwind。

我还尝试创建一个显式strand并在以相同的结果停止之前调度一个Socket.close()。

这种方法有问题吗？

Answer 1

我在尝试优雅地停止类似的服务器时遇到问题(stackoverflow.com/questions/50833730/... – 金属狐狸 4 小时前

这是一个最小的更改，显示了如何处理

• 关闭会话的"退出"命令
• 关闭服务器命令(因此它停止接受连接并在最后一个会话退出后终止(

住在科里鲁

#include <boost/asio.hpp>
#include <iostream>
using boost::asio::ip::tcp;
using boost::system::error_code;
using boost::asio::streambuf;
int main() {
boost::asio::io_service svc;
tcp::acceptor a(svc);
a.open(tcp::v4());
a.set_option(tcp::acceptor::reuse_address(true));
a.bind({{}, 6767}); // bind to port 6767 on localhost
a.listen(5);
using session = std::shared_ptr<tcp::socket>;
std::function<void()>        do_accept;
std::function<void(session)> do_session;
do_session = [&](session s) {
// do a read
auto buf = std::make_shared<boost::asio::streambuf>();
async_read_until(*s, *buf, "n", [&,s,buf](error_code ec, size_t /*bytes*/) {
if (ec)
std::cerr << "read failed: " << ec.message() << "n";
else {
std::istream is(buf.get());
std::string line;
while (getline(is, line)) // FIXME being sloppy with partially read lines
{
async_write(*s, boost::asio::buffer("Ackn", 4), [&,s,buf](error_code ec, size_t) {
if (ec) std::cerr << "write failed: " << ec.message() << "n";
});
if (line == "Exit") {
std::cout << "Exit receivedn";
return;
}
if (line == "Shutdown") {
std::cout << "Server shutdown requestedn";
a.close();
return;
}
}
do_session(s); // full duplex, can read while writing, using a second buffer
}
});
};
do_accept = [&] {
auto s = std::make_shared<session::element_type>(svc);
a.async_accept(*s, [&,s](error_code ec) {
if (ec)
std::cerr << "accept failed: " << ec.message() << "n";
else {
do_session(s);
do_accept(); // accept the next
}
});
};
do_accept(); // kick-off
svc.run();   // wait for shutdown (Ctrl-C or failure)
}

注意示例会话

echo -en "hello worldnExitn"     | netcat 127.0.0.1 6767
echo -en "hello worldnShutdownn" | netcat 127.0.0.1 6767

印刷

Ack
Ack
Ack
Ack
Exit received
Server shutdown requested
accept failed: Operation canceled

终止命令

如果你想要一个主动关闭所有打开的会话并关闭服务器的"终止"命令，你必须

• 保留会话列表
• 或使用信号

您可以在此处查看这两种方法的代码： 提升 ASIO：向所有连接的客户端发送消息

与当前示例集成的最简单方法：

住在科里鲁

#include <boost/asio.hpp>
#include <iostream>
#include <list>
using boost::asio::ip::tcp;
using boost::system::error_code;
using boost::asio::streambuf;
int main() {
boost::asio::io_service svc;
tcp::acceptor a(svc);
a.open(tcp::v4());
a.set_option(tcp::acceptor::reuse_address(true));
a.bind({{}, 6767}); // bind to port 6767 on localhost
a.listen(5);
using session = std::shared_ptr<tcp::socket>;
using sessref = std::weak_ptr<tcp::socket>;
std::function<void()>        do_accept;
std::function<void(session)> do_session;
std::list<sessref> session_list;
auto garbage_collect_sessions = [&session_list] {
session_list.remove_if(std::mem_fn(&sessref::expired));
};
do_session = [&](session s) {
// do a read
auto buf = std::make_shared<boost::asio::streambuf>();
async_read_until(*s, *buf, "n", [&,s,buf](error_code ec, size_t /*bytes*/) {
if (ec)
std::cerr << "read failed: " << ec.message() << "n";
else {
std::istream is(buf.get());
std::string line;
while (getline(is, line)) // FIXME being sloppy with partially read lines
{
async_write(*s, boost::asio::buffer("Ackn", 4), [&,s,buf](error_code ec, size_t) {
if (ec) std::cerr << "write failed: " << ec.message() << "n";
});
if (line == "Exit") {
std::cout << "Exit receivedn";
return;
}
if (line == "Shutdown") {
std::cout << "Server shutdown requestedn";
a.close();
return;
}
if (line == "Terminate") {
std::cout << "Server termination requestedn";
a.close();
for (auto wp : session_list) {
if (auto session = wp.lock())
session->close();
}
return;
}
}
do_session(s); // full duplex, can read while writing, using a second buffer
}
});
};
do_accept = [&] {
auto s = std::make_shared<session::element_type>(svc);
a.async_accept(*s, [&,s](error_code ec) {
if (ec)
std::cerr << "accept failed: " << ec.message() << "n";
else {
garbage_collect_sessions();
session_list.push_back(s);
do_session(s);
do_accept(); // accept the next
}
});
};
do_accept(); // kick-off
svc.run();   // wait for shutdown (Ctrl-C or failure)
}

它显然使用session_list来实现"Terminate"命令：

if (line == "Terminate") {
std::cout << "Server termination requestedn";
a.close();
for (auto wp : session_list) {
if (auto session = wp.lock())
session->close();
}
return;
}