Boost::Asio - 抛出 get_io_service 异常

Posted 2023-02-21

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【中文标题】Boost::Asio - 抛出 get_io_service 异常【英文标题】：Boost::Asio - get_io_service exception thrown 【发布时间】：2015-09-04 20:14:08 【问题描述】：

谁能向我解释为什么当我想调用 get_io_service() 时出现以下异常？

我看到在启动时接受器已初始化，但是当客户端想要连接并且服务器想要打开新连接时，接受器有一些随机数。我不知道为什么会这样。

我的代码：

main.cpp

#include "TServer.h"
#include "TDatabase.h"
#include "Includes.h"
#include "Structures.h"

int main()

try

    std::cout << "========================================" << std::endl
        << "= Game Server v1.0 by Gravity1        =" << std::endl
        << "========================================" << std::endl;

    boost::asio::io_service io_service;
    Database database;
    std::vector<std::vector<TServer>> Server;
    srand(time(0));

    boost::property_tree::ptree pt;
    boost::property_tree::ini_parser::read_ini("game_server_config.ini", pt);

    database.host = pt.get<std::string>("DATABASE.HOST");
    database.username = pt.get<std::string>("DATABASE.USER");
    database.password = pt.get<std::string>("DATABASE.PASS");
    database.schema = pt.get<std::string>("DATABASE.SCHEMA");

    std::shared_ptr<TDatabase> Database_ptr = std::make_shared<TDatabase>(database);

    Database_ptr->Connect();

    short server_count = pt.get<short>("GAME_SERVER.SERVER_COUNT");

    if (server_count > 0)
        Server.resize(server_count);

    for (int i = 0; i < server_count; i++)
    
        short channel_count = pt.get<short>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL_COUNT");

        for (int j = 0; j < channel_count; j++)
        
            Canal CanalTemp;
            CanalTemp.ip = pt.get<std::string>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_IP");
            CanalTemp.port = pt.get<short>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_PORT");
            boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::address::from_string(CanalTemp.ip), CanalTemp.port);
            Server[i].emplace_back(io_service, Database_ptr,endpoint);
        
    

    io_service.run();


catch (std::exception &e)

    std::cerr << e.what() << std::endl;


std::cin.get();
return 0;

TServer.cpp

TServer::TServer(boost::asio::io_service &io_service,std::shared_ptr<TDatabase> database, const boost::asio::ip::tcp::endpoint &endpoint) :
acceptor(io_service,endpoint)

Accept_Connection();


void TServer::Accept_Connection()

Connection = std::make_shared<TSession>(acceptor.get_io_service(),Database);
acceptor.async_accept(*(Connection->Socket()),(boost::bind(&TServer::Handle_Connection, this, Connection, boost::asio::placeholders::error)));


void TServer::Handle_Connection(std::shared_ptr<TSession> Connection, const boost::system::error_code &error)

if (!error)

    Connection->Start();
    Accept_Connection();

【问题讨论】：

也许你忘了给acceptor.listen()打电话？ livecoding.tv/sehe (experiment) 【参考方案1】：

问题很简单。

您将TServers 放置在向量的后面。当您这样做时，它将（可能）重新分配，使程序其他部分中保存的引用无效。见Iterator invalidation rules

在您的情况下，会立即保留这样的引用，因为 Accept_Connection() 是从构造函数中调用的，并且它绑定s 到 this 指针。请记住，this 指针指向 向量内 TServer 元素的地址。

哎呀。当您的完成处理程序触发时，该元素是/可能已被重新分配。所以指针只是悬空而你有Undefined Behaviour。

你可以用不同的方式修复它：

将向量替换为可确保插入时参考稳定性的容器。例如，您可以只使用list<>：

std::list<std::list<TServer> > servers;
if (server_count > 0)
    servers.resize(server_count);

auto current_server = servers.begin();

for (int i = 0; i < server_count; i++, ++current_server) 
    short channel_count = pt.get<short>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL_COUNT");

    for (int j = 0; j < channel_count; j++) 
        Canal CanalTemp;
        CanalTemp.ip   = pt.get<std::string>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_IP");
        CanalTemp.port = pt.get<short>("GAME_SERVER.SERVER_"       + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_PORT");
        tcp::endpoint endpoint(boost::asio::ip::address::from_string(CanalTemp.ip), CanalTemp.port);

        current_server->emplace_back(io_service, Database_ptr, endpoint);

或者，您可以将初始绑定推迟到所有频道都添加到所有服务器之后：

TServer(boost::asio::io_service &io_service, std::shared_ptr<TDatabase> database, const boost::asio::ip::tcp::endpoint &endpoint)
        : acceptor(io_service, endpoint), database(database)

    //Accept_Connection();

在io_service::run() 之前明确地这样做：

for(auto& server: servers)
    for(auto& channel: server)
        channel.Accept_Connection();

io_service.run();

注意：事实上，在惯用的 Asio 代码中，直接从构造函数中运行异步操作通常不可能。看例如在TSession 类型；它无法将完成处理程序绑定到成员函数，因为在构造函数 ("Note that prior to calling shared_from_this on an object t, there must be a shared_ptr that owns t.") 中不允许 shared_from_this()。

两者都有效。我在这里选择第一个：

Live On Coliru

#include <boost/asio.hpp>
#include <boost/make_shared.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/bind.hpp>
#include <iostream>
// for iterator and reference stability (see:
// https://***.com/questions/6438086/iterator-invalidation-rules)
#include <list> 

using tcp = boost::asio::ip::tcp;

struct Canal 
    std::string ip;
    int port;
;

struct Database 
    std::string host, username, password, schema;
;

struct TDatabase 
    TDatabase(Database config) : details(config) 

    void Connect() 
        std::cout 
            << "Connecting to fake database " << details.host << "/" << details.schema
            << " with user " << details.username << " and password '" << std::string(details.password.size(), '*') << "'\n";
    
  private:
    Database details;
;

struct TSession : std::enable_shared_from_this<TSession> 
    TSession(boost::asio::io_service& svc, std::shared_ptr<TDatabase> db) :
        _svc(svc), _socket(_svc), _db(db) 

    tcp::socket& Socket()  return _socket; 

    void Start() 
        boost::asio::async_read(_socket, _sb, 
                boost::bind(&TSession::HandleReceived, shared_from_this(),
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
     

    void HandleReceived(boost::system::error_code ec, size_t bytes_transferred) 
        if (!ec || boost::asio::error::eof == ec) 
            std::cout << "Received from " << _socket.remote_endpoint() << ": '" << &_sb << "'\n";
         else
        
            std::cout << "Error reading from peer: " << ec.message() << "\n";
        
    

  private:
    boost::asio::io_service& _svc;
    tcp::socket _socket;
    std::shared_ptr<TDatabase> _db;
    boost::asio::streambuf _sb;
;

struct TServer 
    tcp::acceptor acceptor;
    std::shared_ptr<TDatabase> database;

    TServer(boost::asio::io_service &io_service, std::shared_ptr<TDatabase> database, const boost::asio::ip::tcp::endpoint &endpoint)
            : acceptor(io_service, endpoint), database(database)
    
        Accept_Connection();
    

    void Accept_Connection() 
        auto Connection = std::make_shared<TSession>(acceptor.get_io_service(), database);
        acceptor.async_accept(Connection->Socket(),
                boost::bind(&TServer::Handle_Connection, this, Connection, boost::asio::placeholders::error));
    

    void Handle_Connection(std::shared_ptr<TSession> Connection, const boost::system::error_code &error) 
        if (!error) 
            Connection->Start();
            Accept_Connection();
         else
            std::cout << "Error: " << error.message() << "\n";
    
;

//#include "TServer.h"
//#include "TDatabase.h"
//#include "Includes.h"
//#include "Structures.h"
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/ini_parser.hpp>

int main() 
    try 
        std::cout << "========================================" << std::endl
                  << "= Game Server v1.0 by Gravity1        =" << std::endl
                  << "========================================" << std::endl;

        boost::asio::io_service io_service;
        Database database;
        std::list<std::list<TServer> > servers;
        srand(time(0));

        boost::property_tree::ptree pt;
        boost::property_tree::read_ini("game_server_config.ini", pt);

        database.host     = pt.get<std::string>("DATABASE.HOST");
        database.username = pt.get<std::string>("DATABASE.USER");
        database.password = pt.get<std::string>("DATABASE.PASS");
        database.schema   = pt.get<std::string>("DATABASE.SCHEMA");

        std::shared_ptr<TDatabase> Database_ptr = std::make_shared<TDatabase>(database);
        Database_ptr->Connect();

        short server_count = pt.get<short>("GAME_SERVER.SERVER_COUNT");

        if (server_count > 0)
            servers.resize(server_count);

        auto current_server = servers.begin();

        for (int i = 0; i < server_count; i++, ++current_server) 
            short channel_count = pt.get<short>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL_COUNT");

            for (int j = 0; j < channel_count; j++) 
                Canal CanalTemp;
                CanalTemp.ip   = pt.get<std::string>("GAME_SERVER.SERVER_" + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_IP");
                CanalTemp.port = pt.get<short>("GAME_SERVER.SERVER_"       + std::to_string(i + 1) + "_CHANNEL" + std::to_string(j + 1) + "_PORT");
                tcp::endpoint endpoint(boost::asio::ip::address::from_string(CanalTemp.ip), CanalTemp.port);

                current_server->emplace_back(io_service, Database_ptr, endpoint);
            
        

        io_service.run();
     
    catch (std::exception &e) 
        std::cerr << e.what() << std::endl;
    

    std::cin.get();

我用了一个配置

[DATABASE]
HOST=localhost
USER=root
PASS=youbet
SCHEMA=my_game

[GAME_SERVER]
SERVER_COUNT=1
SERVER_1_CHANNEL_COUNT=2
SERVER_1_CHANNEL1_IP=127.0.0.1
SERVER_1_CHANNEL1_PORT=6767
SERVER_1_CHANNEL2_IP=127.0.0.2
SERVER_1_CHANNEL2_PORT=6868

当在两个通道（端口 6767 和 6868）上运行客户端时，会打印出“无休止”的重复：

========================================
= Game Server v1.0 by Gravity1        =
========================================
Connecting to fake database localhost/my_game with user root and password '******'
Received from 127.0.0.1:54942: 'hello channel
'
Received from 127.0.0.1:37217: 'hello OTHER channel
'
Received from 127.0.0.1:54945: 'hello channel
'
Received from 127.0.0.1:37220: 'hello OTHER channel
'
Received from 127.0.0.1:54947: 'hello channel
'
Received from 127.0.0.1:37222: 'hello OTHER channel
'
Received from 127.0.0.1:54949: 'hello channel
'
Received from 127.0.0.1:37224: 'hello OTHER channel
'
Received from 127.0.0.1:54951: 'hello channel
'
Received from 127.0.0.1:37226: 'hello OTHER channel
'
Received from 127.0.0.1:54953: 'hello channel
'
Received from 127.0.0.1:37228: 'hello OTHER channel
'
Received from 127.0.0.1:54955: 'hello channel
'
Received from 127.0.0.1:37230: 'hello OTHER channel
'
Received from 127.0.0.1:54957: 'hello channel
'
Received from 127.0.0.1:37232: 'hello OTHER channel
'

【讨论】：

【参考方案2】：

完全不相关，但您的配置格式确实要求采用分层格式，例如 JSON 或 XML。

为了好玩，我将该示例重构为使用 XML：

<?xml version="1.0"?>
<CONFIG>
  <DATABASE>
    <HOST>localhost</HOST>
    <USER>root</USER>
    <PASS>youbet</PASS>
    <SCHEMA>my_game</SCHEMA>
  </DATABASE>
  <GAME_SERVER>
    <SERVER>
      <CHANNEL>
        <IP>127.0.0.1</IP>
        <PORT>6767</PORT>
      </CHANNEL>
      <CHANNEL>
        <IP>127.0.0.2</IP>
        <PORT>6868</PORT>
      </CHANNEL>
    </SERVER>
  </GAME_SERVER>
</CONFIG>

您可以使用以下 sn-ps 阅读：

boost::property_tree::ptree pt;
boost::property_tree::read_xml("game_server_config.xml", pt);

if (auto dbconfig = pt.get_child_optional("CONFIG.DATABASE")) 
    database.host     = dbconfig->get<std::string>("HOST");
    database.username = dbconfig->get<std::string>("USER");
    database.password = dbconfig->get<std::string>("PASS");
    database.schema   = dbconfig->get<std::string>("SCHEMA");

对于服务器/频道：

for (auto& serverconfig: pt.get_child("CONFIG.GAME_SERVER")) 
    if ("SERVER" != serverconfig.first)
        continue;

    servers.emplace_back();
    auto& current_server = servers.back();

    for (auto& channelconfig: serverconfig.second) 
        if ("CHANNEL" != channelconfig.first)
            continue;

        Canal CanalTemp;
        CanalTemp.ip   = channelconfig.second.get<std::string>("IP");
        CanalTemp.port = channelconfig.second.get<short>("PORT");
        tcp::endpoint endpoint(boost::asio::ip::address::from_string(CanalTemp.ip), CanalTemp.port);

        current_server.emplace_back(io_service, Database_ptr, endpoint);

也看到 Live On Coliru :)

#include <boost/asio.hpp>
#include <boost/make_shared.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/bind.hpp>
#include <iostream>
// for iterator and reference stability (see:
// http://***.com/questions/6438086/iterator-invalidation-rules)
#include <list> 

using tcp = boost::asio::ip::tcp;

struct Canal 
    std::string ip;
    int port;
;

struct Database 
    std::string host, username, password, schema;
;

struct TDatabase 
    TDatabase(Database config) : details(config) 

    void Connect() 
        std::cout 
            << "Connecting to fake database " << details.host << "/" << details.schema
            << " with user " << details.username << " and password '" << std::string(details.password.size(), '*') << "'\n";
    
  private:
    Database details;
;

struct TSession : std::enable_shared_from_this<TSession> 
    TSession(boost::asio::io_service& svc, std::shared_ptr<TDatabase> db) :
        _svc(svc), _socket(_svc), _db(db) 

    tcp::socket& Socket()  return _socket; 

    void Start() 
        boost::asio::async_read(_socket, _sb, 
                boost::bind(&TSession::HandleReceived, shared_from_this(),
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
     

    void HandleReceived(boost::system::error_code ec, size_t bytes_transferred) 
        if (!ec || boost::asio::error::eof == ec) 
            std::cout << "Received from " << _socket.remote_endpoint() << ": '" << &_sb << "'\n";
         else
        
            std::cout << "Error reading from peer: " << ec.message() << "\n";
        
    

  private:
    boost::asio::io_service& _svc;
    tcp::socket _socket;
    std::shared_ptr<TDatabase> _db;
    boost::asio::streambuf _sb;
;

struct TServer 
    tcp::acceptor acceptor;
    std::shared_ptr<TDatabase> database;

    TServer(boost::asio::io_service &io_service, std::shared_ptr<TDatabase> database, const boost::asio::ip::tcp::endpoint &endpoint)
            : acceptor(io_service, endpoint), database(database)
    
        Accept_Connection();
    

    void Accept_Connection() 
        auto Connection = std::make_shared<TSession>(acceptor.get_io_service(), database);
        acceptor.async_accept(Connection->Socket(),
                boost::bind(&TServer::Handle_Connection, this, Connection, boost::asio::placeholders::error));
    

    void Handle_Connection(std::shared_ptr<TSession> Connection, const boost::system::error_code &error) 
        if (!error) 
            Connection->Start();
            Accept_Connection();
         else
            std::cout << "Error: " << error.message() << "\n";
    
;

//#include "TServer.h"
//#include "TDatabase.h"
//#include "Includes.h"
//#include "Structures.h"
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>

int main() 
    try 
        std::cout << "========================================" << std::endl
                  << "= Game Server v1.0 by Gravity1        =" << std::endl
                  << "========================================" << std::endl;

        boost::asio::io_service io_service;
        Database database;
        std::list<std::list<TServer> > servers;
        srand(time(0));

        boost::property_tree::ptree pt;
        boost::property_tree::read_xml("game_server_config.xml", pt);

        if (auto dbconfig = pt.get_child_optional("CONFIG.DATABASE")) 
            database.host     = dbconfig->get<std::string>("HOST");
            database.username = dbconfig->get<std::string>("USER");
            database.password = dbconfig->get<std::string>("PASS");
            database.schema   = dbconfig->get<std::string>("SCHEMA");
        

        std::shared_ptr<TDatabase> Database_ptr = std::make_shared<TDatabase>(database);
        Database_ptr->Connect();

        for (auto& serverconfig: pt.get_child("CONFIG.GAME_SERVER")) 
            if ("SERVER" != serverconfig.first)
                continue;

            servers.emplace_back();
            auto& current_server = servers.back();

            for (auto& channelconfig: serverconfig.second) 
                if ("CHANNEL" != channelconfig.first)
                    continue;

                Canal CanalTemp;
                CanalTemp.ip   = channelconfig.second.get<std::string>("IP");
                CanalTemp.port = channelconfig.second.get<short>("PORT");
                tcp::endpoint endpoint(boost::asio::ip::address::from_string(CanalTemp.ip), CanalTemp.port);

                current_server.emplace_back(io_service, Database_ptr, endpoint);
            
        

        io_service.run();
     
    catch (std::exception &e) 
        std::cerr << e.what() << std::endl;
    

    std::cin.get();

打印

========================================
= Game Server v1.0 by Gravity1        =
========================================
Connecting to fake database localhost/my_game with user root and password '******'
Received from 127.0.0.1:55712: 'hello channel
'
Received from 127.0.0.1:37987: 'hello OTHER channel
'
Received from 127.0.0.1:55714: 'hello channel
'
Received from 127.0.0.1:37989: 'hello OTHER channel
'
Received from 127.0.0.1:55716: 'hello channel
'

等等

【讨论】：

谢谢。它现在完美运行！再次感谢您的帮助；）。

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