Asio and HTTP keep-alive

Question

我正在尝试使用asio实现一个Web服务器，但尽管我将接受器设置为keep-alive，但在接收连接后，发送响应后连接套接字总是关闭的，即使我重新从套接字读取（为了实现http中的keep-alive）。

我已经尝试在代码中插入printf，但由于某种原因，在写入响应后，当客户端建立新连接时，它会调用我的套接字上的acceptor，它不应该只是使用旧套接字并从中重新读取，而不是调用acceptor吗？

或者我正在错误地使用keep-alive功能...

代码的相关部分如下：

#include "connection.hpp"
#include <vector>
#include <boost/bind.hpp>
#include "connection_manager.hpp"
#include "request_handler.hpp"
#include <iostream>

namespace http {
namespace server {

connection::connection(asio::io_service& io_service,
    connection_manager& manager, request_handler& handler)
  : socket_(io_service),
    connection_manager_(manager),
    request_handler_(handler),
    request_parser_(new http_visitor()),
    keep_alive_(true)
{
}

asio::ip::tcp::socket& connection::socket()
{
  return socket_;
}

void connection::start()
{
  socket_.async_read_some(asio::buffer(buffer_),
      boost::bind(&connection::handle_read, shared_from_this(),
        asio::placeholders::error,
        asio::placeholders::bytes_transferred));
  std::cout << "In connection start" << std::endl;
}

void connection::stop()
{
  socket_.close();
}

void connection::handle_read(const asio::error_code& e,
    std::size_t bytes_transferred)
{
  if (!e)
  {
    boost::tribool result;
    boost::tie(result, boost::tuples::ignore) = request_parser_.parse(
        request_, buffer_.data(), buffer_.data() + bytes_transferred);

    if (result)
    {
      request_handler_.handle_request(request_, reply_);

      std::vector<header>::iterator hdr_it;

      for(hdr_it = request_.headers.begin(); hdr_it != request_.headers.end();     hdr_it++)
      {
            if( (hdr_it->name.compare("Connection" ) == 0) && 
                (hdr_it->value.compare("close" ) == 0 ) )
        { keep_alive_ = false; }   
      }

      asio::async_write(socket_, reply_.to_buffers(),
                    boost::bind(&connection::handle_write, shared_from_this(),
                    asio::placeholders::error));
    }
    else if (!result)
    {
      reply_ = reply::stock_reply(reply::bad_request);
      asio::async_write(socket_, reply_.to_buffers(),
          boost::bind(&connection::handle_write, shared_from_this(),
            asio::placeholders::error));
    }
    else
    {
      socket_.async_read_some(asio::buffer(buffer_),
          boost::bind(&connection::handle_read, shared_from_this(),
            asio::placeholders::error,
            asio::placeholders::bytes_transferred));
    }
  }
  else if (e != asio::error::operation_aborted)
  {
    connection_manager_.stop(shared_from_this());
  }
}

void connection::handle_write(const asio::error_code& e)
{
  if (!e)
  {

    std::cout << keep_alive_ << std::endl;
    if(keep_alive_)
    {
      buffer_.assign(0);
      request_.clear();
      keep_alive_ = false;
      start();
    }
    else
    {
      socket_.close();
    }  
  }

  if (e != asio::error::operation_aborted)
  {
    connection_manager_.stop(shared_from_this());
  }
}
}
}

并且

#include "server.hpp"
#include <boost/bind.hpp>
#include <signal.h>
#include <iostream>

namespace http {
namespace server {

server::server(const std::string& address, const std::string& port,
    const std::string& doc_root)
  : io_service_(),
    signals_(io_service_),
    acceptor_(io_service_),
    connection_manager_(),
    new_connection_(new connection(io_service_, connection_manager_, request_handler_)),
    request_handler_(doc_root)
{
  signals_.add(SIGINT);
  signals_.add(SIGTERM);
  signals_.async_wait(boost::bind(&server::handle_stop, this));

  // Open the acceptor with the option to reuse the address (i.e. SO_REUSEADDR).
  asio::ip::tcp::resolver resolver(io_service_);
  asio::ip::tcp::resolver::query query(address, port);
  asio::ip::tcp::endpoint endpoint = *resolver.resolve(query);
  acceptor_.open(endpoint.protocol());
  acceptor_.set_option(asio::ip::tcp::acceptor::reuse_address(true));
  acceptor_.set_option(asio::ip::tcp::acceptor::keep_alive(true));
  acceptor_.bind(endpoint);
  acceptor_.listen();
  acceptor_.async_accept(new_connection_->socket(),
      boost::bind(&server::handle_accept, this,
        asio::placeholders::error));
}

void server::run()
{
    io_service_.run();
}

void server::stop()
{
  io_service_.post(boost::bind(&server::handle_stop, this));
}

void server::handle_accept(const asio::error_code& e)
{
  if (!e)
  {
   std::cout << "In accept" << std::endl;
    connection_manager_.start(new_connection_);
    new_connection_.reset(new connection(io_service_, connection_manager_,     request_handler_));
    acceptor_.async_accept(new_connection_->socket(),
        boost::bind(&server::handle_accept, this, asio::placeholders::error));
  }
}

void server::handle_stop()
{
  acceptor_.close();
  connection_manager_.stop_all();
}

} // namespace server
} // namespace http

在这段代码中，有三个打印语句："连接开始"，"正在接收连接"和"连接开始"。但当同一客户端再次向服务器发起连接时，应该只有第一个"连接开始"语句。

- Coyote21

---

你的 connection_manager_.start() 函数是做什么用的？ - Nick

@Nick 它在新连接上调用start。 - Coyote21

Answer 1

没有完整的代码，我猜测new_connection_是一个shared_ptr，并且您没有在任何地方保留对它的引用。这将导致智能指针删除连接并关闭套接字。

在您的连接析构函数中加入断点，并检查是否属实。

没有看到更多的代码，很难诊断问题。

- Nick