Question

操作系统：linux 64位ARCH。

提升：1.46.1

编译器：clang ++ / GCC。

我有一个代码片段，其中包含一个以boost :: asio为例（Chat Server）建模的tcp接受器。但是，当我运行片段时，没有监听TCP套接字出现在netstat监听（linux）中。但是，聊天服务器示例在编译时会显示。有人可以指出我做错了什么吗？

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/bind.hpp>
#include <list>
#include <iostream>


using namespace boost::asio;
  using namespace boost::asio::ip;

  class ClientConnection
  {
  public:
    ClientConnection(io_service & io_s)
      : m_socket(io_s) {}
    tcp::socket & socket() { return m_socket; }
  private:
    tcp::socket m_socket;  
  };

  typedef boost::shared_ptr<ClientConnection> client_connection_ptr;

  class ClientConnectionAcceptor
  {
  public:
    ClientConnectionAcceptor(unsigned short port)
      : m_io_service(),
        m_port(port),
        m_endpoint(tcp::v4(), m_port),
        m_acceptor(m_io_service, m_endpoint)
    {
      std::cout << "acceptor is open : " << m_acceptor.is_open() << std::endl;
      client_connection_ptr ccp(new ClientConnection(m_io_service));

      m_acceptor.async_accept(  
        ccp->socket(),
        boost::bind(&ClientConnectionAcceptor::handle_accept,this, 
        ccp, placeholders::error));
    } 

    void handle_accept(client_connection_ptr ccp, const boost::system::error_code & error)
    {
      std::cout << "in handle_accept" << std::endl;  
      if(!error)
      {
       // m_rpc_oracle.AddNewClient(ccp);
        client_connection_ptr new_ccp(new ClientConnection(m_io_service));
        m_acceptor.async_accept(  
          new_ccp->socket(),
          boost::bind(&ClientConnectionAcceptor::handle_accept,this, 
          ccp, placeholders::error));

      }
    }

    io_service & io_service() { return m_io_service; }
  private:
    boost::asio::io_service m_io_service;
    tcp::endpoint m_endpoint;
    tcp::acceptor m_acceptor;
    unsigned short m_port;
  };


int main()
{
  ClientConnectionAcceptor acceptor(5000);
  acceptor.io_service().run();
}

Answer 1

我发现如果我将endpoint和acceptor更改为共享指针，我可以在我的Windows机器上运行它，而不是通过在构造函数中将它们作为参数传递来创建它们，我专门在构造函数中创建了共享指针。我不确定为什么会这样。我唯一的猜测是，也许不能保证构造函数参数按它们出现的顺序传递或创建，因此您可能会尝试使用未正确初始化的acceptor创建endpoint然而？这真是我唯一的猜测。如果这对您有用，请告诉我。我可以通过端口localhost上的5000成功连接。

如果没有这些更改，我尝试通过localhost连接的客户端告诉我连接被主动拒绝。然而，这种安排是成功的，并且似乎与原始代码的偏差尽可能小。希望它有所帮助。

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/bind.hpp>
#include <list>
#include <iostream>

using namespace boost::asio;
using namespace boost::asio::ip;

class ClientConnection
{
public:
  ClientConnection(io_service & io_s)
    : m_socket(io_s) {}
  tcp::socket & socket() { return m_socket; }
private:
  tcp::socket m_socket;  
};

typedef boost::shared_ptr<ClientConnection> client_connection_ptr;

class ClientConnectionAcceptor
{
public:
  ClientConnectionAcceptor(unsigned short port)
    : m_io_service(),
    m_port(port)
  {
    // now initializing endpoint and acceptor as shared pointers inside the constructor
    m_endpoint = boost::shared_ptr<tcp::endpoint>(new tcp::endpoint(tcp::v4(), m_port));
    m_acceptor = boost::shared_ptr<tcp::acceptor>(new tcp::acceptor(m_io_service, *m_endpoint));

    std::cout << "acceptor is open : " << m_acceptor->is_open() << std::endl;
    client_connection_ptr ccp(new ClientConnection(m_io_service));

    m_acceptor->async_accept(  
      ccp->socket(),
      boost::bind(&ClientConnectionAcceptor::handle_accept,this, 
      ccp, placeholders::error));
  } 

  void handle_accept(client_connection_ptr ccp, const boost::system::error_code & error)
  {
    std::cout << "in handle_accept" << std::endl;  
    if(!error)
    {
      // m_rpc_oracle.AddNewClient(ccp);
      client_connection_ptr new_ccp(new ClientConnection(m_io_service));
      m_acceptor->async_accept(  
        new_ccp->socket(),
        boost::bind(&ClientConnectionAcceptor::handle_accept,this, 
        ccp, placeholders::error));

    }
  }

  io_service & io_service() { return m_io_service; }
private:
  boost::asio::io_service m_io_service;
  boost::shared_ptr<tcp::endpoint> m_endpoint;
  boost::shared_ptr<tcp::acceptor> m_acceptor;
  unsigned short m_port;
};


int main()
{
  ClientConnectionAcceptor acceptor(5000);
  acceptor.io_service().run();
}

编辑

经过一些进一步的调查，发现问题实际上与ClientConnectionAcceptor类的初始化列表有关。在类定义中，成员m_port在 m_endpoint和m_acceptor之后被声明为。因此，即使初始化程序列表似乎在创建endpoint和acceptor 之前设置了端口号，实际上，端口值无效或已初始化直到之后endpoint和acceptor已经创建。更改类定义以在m_port和endpoint之前声明成员acceptor可以解决问题。

Answer 2

编译代码时出错

async_accept.cc:56: error: declaration of ‘boost::asio::io_service& ClientConnectionAcceptor::io_service()’
/opt/local/include/boost/asio/io_service.hpp:186: error: changes meaning of ‘io_service’ from ‘class boost::asio::io_service’

改变

io_service & io_service() { return m_io_service; }

到

io_service & get_io_service() { return m_io_service; }

似乎解决了编译器故障。运行生成的二进制文件为我显示netstat -l -t中的侦听套接字。

Boost ASIO异步接收器未打开侦听端口

2 个答案: