• boost asio异步读写网络聊天程序client 实例具体解释


    
    

    boost官方文档中聊天程序实例解说

    数据包格式chat_message.hpp

    <pre name="code" class="cpp"><h3>数据包chat_message.hpp</h3>
    // chat_message.hpp
    // ~~~~~~~~~~~~~~~~
    //
    // Copyright (c) 2003-2013 Christopher M. Kohlhoff (chris at kohlhoff dot com)
    //
    // Distributed under the Boost Software License, Version 1.0. (See accompanying
    // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
    //实例源于http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio/examples/cpp03_examples.html 文档中没有凝视,自己在///開始看的时候也走了点弯路,本文对该源代码写了具体的凝视,希望能让后来者们少走些弯路。
    //首先看看数据包的结构:
    //数据包分为两个部分。首先是报头占4bytes,每一byte表示一个数字。也就是最多能表示的出9999,不足在前填0;
    // 数据包头的数字表示数据部分的长度大小。

    #ifndef CHAT_MESSAGE_HPP #define CHAT_MESSAGE_HPP #include <cstdio> #include <cstdlib> #include <cstring> class chat_message { public: enum { header_length = 4 }; enum { max_body_length = 512 }; chat_message() : body_length_(0) { } const char* data() const { return data_; } char* data() { return data_; } size_t length() const { return header_length + body_length_; } const char* body() const { return data_ + header_length; } char* body() { return data_ + header_length; } size_t body_length() const { return body_length_; } void body_length(size_t new_length) { body_length_ = new_length; if (body_length_ > max_body_length) body_length_ = max_body_length; } bool decode_header()//将报头的4字节字符串转换成数字 { using namespace std; // For strncat and atoi. char header[header_length + 1] = ""; strncat(header, data_, header_length); body_length_ = atoi(header); if (body_length_ > max_body_length) { body_length_ = 0; return false; } return true; } void encode_header()//把数据部分大小编码成字符串 { using namespace std; // For sprintf and memcpy. char header[header_length + 1] = ""; sprintf(header, "%4d", body_length_); memcpy(data_, header, header_length); } private: char data_[header_length + max_body_length]; size_t body_length_; }; #endif // CHAT_MESSAGE_HPP

    
    



    聊天客户端chat_client.cpp

    ///////////////////////////////////////////////////////////////////////////////////////////////////////
    
    
    <h3>
    </h3><h3>
    	<span style="white-space:pre-wrap">聊天客户端chat_client.cpp</span>
    </h3>
    <pre>
    
    
    ///////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // chat_client.cpp
    // ~~~~~~~~~~~~~~~
    //
    // Copyright (c) 2003-2013 Christopher M. Kohlhoff (chris at kohlhoff dot com)
    //
    // Distributed under the Boost Software License, Version 1.0. (See accompanying
    // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
    //
    //boost开发文档中实时聊天程序的客户端
    //实现的大致思路是:在创建的客户端实例中初始化socket、连接server端,而且不断的进行着异步读操作(从server端读数据)
    //在主线程中,从console中不断读取要被发送的消息,而且把这些消息post至io_service,然后进行异步写操作
    //读写socket都是用异步操作
    //这样的方法不同于分别开一个读线程,一个写线程, 它的优势是线程不会一直等待读写数据,在并发数大的情况下通过异步读写能提高资源利用率
    
    
    #include <cstdlib>
    #include <deque>
    #include <iostream>
    #include <boost/bind.hpp>
    #include <boost/asio.hpp>
    #include <boost/thread/thread.hpp>
    #include "chat_message.hpp"
    
    using boost::asio::ip::tcp;
    
    typedef std::deque<chat_message> chat_message_queue;
    
    class chat_client
    {
    public:
      chat_client(boost::asio::io_service& io_service,
          tcp::resolver::iterator endpoint_iterator)
        : io_service_(io_service),
          socket_(io_service) //使得成员函数能直接使用这些变量
      {
        boost::asio::async_connect(socket_, endpoint_iterator,
            boost::bind(&chat_client::handle_connect, this,
              boost::asio::placeholders::error)); //全部的操作都採用异步的方式
      }
    
      void write(const chat_message& msg)
      {
        io_service_.post(boost::bind(&chat_client::do_write, this, msg)); //将消息主动投递给io_service
      }
    
      void close()
      {
        io_service_.post(boost::bind(&chat_client::do_close, this)); //这个close函数是客户端要主动终止时调用  do_close函数是从server端
                                                                    //读数据失败时调用
      }
    
    private:
    
      void handle_connect(const boost::system::error_code& error)
      {
        if (!error)
        {
          boost::asio::async_read(socket_,
              boost::asio::buffer(read_msg_.data(), chat_message::header_length), //读取数据报头
              boost::bind(&chat_client::handle_read_header, this,
                boost::asio::placeholders::error));
        }
      }
    
      void handle_read_header(const boost::system::error_code& error)
      {
        if (!error && read_msg_.decode_header()) //分别处理数据报头和数据部分
        {
          boost::asio::async_read(socket_,
              boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),//读取数据包数据部分
              boost::bind(&chat_client::handle_read_body, this,
                boost::asio::placeholders::error));
        }
        else
        {
          do_close();
        }
      }
    
      void handle_read_body(const boost::system::error_code& error)
      {
        if (!error)
        {
          std::cout.write(read_msg_.body(), read_msg_.body_length()); //输出消息
          std::cout << "
    ";
          boost::asio::async_read(socket_, 
              boost::asio::buffer(read_msg_.data(), chat_message::header_length), //在这里读取下一个数据包头
              boost::bind(&chat_client::handle_read_header, this,  
                boost::asio::placeholders::error)); //完毕一次读操作(处理完一个数据包)  进行下一次读操作
        }
        else
        {
          do_close();
        }
      }
    
      void do_write(chat_message msg)
      {
        bool write_in_progress = !write_msgs_.empty(); //空的话变量为false
        write_msgs_.push_back(msg); //把要写的数据push至写队列
        if (!write_in_progress)//队列初始为空 push一个msg后就有一个元素了
        {
          boost::asio::async_write(socket_,
              boost::asio::buffer(write_msgs_.front().data(),
                write_msgs_.front().length()),
              boost::bind(&chat_client::handle_write, this, 
                boost::asio::placeholders::error));
        }
      }
    
      void handle_write(const boost::system::error_code& error)//第一个消息单独处理,剩下的才更好操作
      {
        if (!error)
        {
          write_msgs_.pop_front();//刚才处理完一个数据 所以要pop一个
          if (!write_msgs_.empty())  
          {
            boost::asio::async_write(socket_,
                boost::asio::buffer(write_msgs_.front().data(),
                  write_msgs_.front().length()),
                boost::bind(&chat_client::handle_write, this,
                  boost::asio::placeholders::error)); //循环处理剩余的消息
          }
        }
        else
        {
          do_close();
        }
      }
    
      void do_close()
      {
        socket_.close();
      }
    
    private:
      boost::asio::io_service& io_service_;
      tcp::socket socket_;
      chat_message read_msg_;
      chat_message_queue write_msgs_;
    };
    
    int main(int argc, char* argv[])
    {
      try
      {
        if (argc != 3)
        {
          std::cerr << "Usage: chat_client <host> <port>
    ";
          return 1;
        }
    
        boost::asio::io_service io_service;
    
        tcp::resolver resolver(io_service);
        tcp::resolver::query query(argv[1], argv[2]); //输入ip(或域名)和端口号
        tcp::resolver::iterator iterator = resolver.resolve(query);
    
        chat_client c(io_service, iterator);
    
        boost::thread t(boost::bind(&boost::asio::io_service::run, &io_service));
    
        char line[chat_message::max_body_length + 1];
        while (std::cin.getline(line, chat_message::max_body_length + 1))
        {
          using namespace std; // For strlen and memcpy.
          chat_message msg;
          msg.body_length(strlen(line));
          memcpy(msg.body(), line, msg.body_length());
          msg.encode_header();
          c.write(msg);
        }
    
        c.close();
        t.join();
      }
      catch (std::exception& e)
      {
        std::cerr << "Exception: " << e.what() << "
    ";
      }
    
      return 0;
    }


    聊天服务器端chat_server.cpp

    //
    // chat_server.cpp
    // ~~~~~~~~~~~~~~~
    //
    // Copyright (c) 2003-2013 Christopher M. Kohlhoff (chris at kohlhoff dot com)
    //
    // Distributed under the Boost Software License, Version 1.0. (See accompanying
    // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
    //
    //服务器端程序,首先开启一个chat_server,用来初始话io_service和chat_room;  服务器每次仅仅开启一个chat_room,chat_room的作用是 1//.保存用户信息  2.实现用户的join和leave  3.保存从每个client接收到的信息  4.将接收到的消息挂到每个clientwrite_msgs队尾
    //每连接上一个client(socket)就开启一个新的chat_session 并增加唯一的chat_room   chat_session中实现分别对每个client的异步读写//操作
    
    #include <algorithm>
    #include <cstdlib>
    #include <deque>
    #include <iostream>
    #include <list>
    #include <set>
    #include <boost/bind.hpp>
    #include <boost/shared_ptr.hpp>
    #include <boost/enable_shared_from_this.hpp>
    #include <boost/asio.hpp>
    #include "chat_message.hpp"
    
    using boost::asio::ip::tcp;
    
    //----------------------------------------------------------------------
    
    typedef std::deque<chat_message> chat_message_queue;
    
    //----------------------------------------------------------------------
    
    class chat_participant
    {
    public:
      virtual ~chat_participant() {}
      virtual void deliver(const chat_message& msg) = 0; //后面须要重载
    };
    
    typedef boost::shared_ptr<chat_participant> chat_participant_ptr;
    
    //----------------------------------------------------------------------
    
    class chat_room
    {
    public:
      void join(chat_participant_ptr participant)
      {
        participants_.insert(participant);
        std::for_each(recent_msgs_.begin(), recent_msgs_.end(),
            boost::bind(&chat_participant::deliver, participant, _1));
      }
    
      void leave(chat_participant_ptr participant)
      {
        participants_.erase(participant);
      }
    
    
    //将从某个client收到的消息挂到 每个client的write_msgs队尾 详细见chat_participant::deliver
    
      void deliver(const chat_message& msg)
    
      {
        recent_msgs_.push_back(msg);
        while (recent_msgs_.size() > max_recent_msgs)
          recent_msgs_.pop_front(); //room中保存的消息数有限
    
        std::for_each(participants_.begin(), participants_.end(),
            boost::bind(&chat_participant::deliver, _1, boost::ref(msg)));
      }
    
    private:
      std::set<chat_participant_ptr> participants_;//用set来保存用户信息
      enum { max_recent_msgs = 100 };
      chat_message_queue recent_msgs_;//用来保存从某个client接收到的信息
    };
    
    //----------------------------------------------------------------------
    
    class chat_session
      : public chat_participant,
        public boost::enable_shared_from_this<chat_session>
    {
    public:
      chat_session(boost::asio::io_service& io_service, chat_room& room)
        : socket_(io_service),
          room_(room)
      {
      }
    
      tcp::socket& socket()
      {
        return socket_;
      }
    
      void start()//每生成一个新的chat_session都会调用
      {
        room_.join(shared_from_this());
        boost::asio::async_read(socket_,
            boost::asio::buffer(read_msg_.data(), chat_message::header_length),
            boost::bind(
              &chat_session::handle_read_header, shared_from_this(),
              boost::asio::placeholders::error)); //异步读client发来的消息
      }
    
      void deliver(const chat_message& msg)
      {
        bool write_in_progress = !write_msgs_.empty();
        write_msgs_.push_back(msg); //把room中保存的消息挂到write_msgs队尾
        if (!write_in_progress)
        {
          boost::asio::async_write(socket_,
              boost::asio::buffer(write_msgs_.front().data(),
                write_msgs_.front().length()), 
              boost::bind(&chat_session::handle_write, shared_from_this(),
                boost::asio::placeholders::error));
        }
      }
    
      void handle_read_header(const boost::system::error_code& error)
      {
        if (!error && read_msg_.decode_header())
        {
          boost::asio::async_read(socket_,
              boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),
              boost::bind(&chat_session::handle_read_body, shared_from_this(),
                boost::asio::placeholders::error));
        }
        else
        {
          room_.leave(shared_from_this());
        }
      }
    
      void handle_read_body(const boost::system::error_code& error)
      {
        if (!error)
        {
          room_.deliver(read_msg_);
          boost::asio::async_read(socket_,
              boost::asio::buffer(read_msg_.data(), chat_message::header_length),
              boost::bind(&chat_session::handle_read_header, shared_from_this(),
                boost::asio::placeholders::error));
        }
        else
        {
          room_.leave(shared_from_this());
        }
      }
    
      void handle_write(const boost::system::error_code& error)
      {
        if (!error)
        {
          write_msgs_.pop_front();
          if (!write_msgs_.empty())
          {
            boost::asio::async_write(socket_,
                boost::asio::buffer(write_msgs_.front().data(),
                  write_msgs_.front().length()),
                boost::bind(&chat_session::handle_write, shared_from_this(),
                  boost::asio::placeholders::error)); //服务器端将收到的消息送给全部的client(广播的方式)
          }
        }
        else
        {
          room_.leave(shared_from_this());
        }
      }
    
    private:
      tcp::socket socket_;
      chat_room& room_;
      chat_message read_msg_;
      chat_message_queue write_msgs_;
    };
    
    typedef boost::shared_ptr<chat_session> chat_session_ptr;
    
    //----------------------------------------------------------------------
    
    class chat_server
    {
    public:
      chat_server(boost::asio::io_service& io_service,
          const tcp::endpoint& endpoint)
        : io_service_(io_service),
          acceptor_(io_service, endpoint) //全局仅仅有一个io_service和一个acceptor
      {
        start_accept();
      }
    
      void start_accept()
      {
        chat_session_ptr new_session(new chat_session(io_service_, room_));
        acceptor_.async_accept(new_session->socket(),
            boost::bind(&chat_server::handle_accept, this, new_session,
              boost::asio::placeholders::error));
      }
    
      void handle_accept(chat_session_ptr session,
          const boost::system::error_code& error)
      {
        if (!error)
        {
          session->start();
        }
    
        start_accept(); //每连接上一个socket都会调用
      }
    
    private:
      boost::asio::io_service& io_service_;
      tcp::acceptor acceptor_;
      chat_room room_; //chat_room中没有重载构造函数 所以会直接调用默认构造函数
    };
    
    typedef boost::shared_ptr<chat_server> chat_server_ptr;
    typedef std::list<chat_server_ptr> chat_server_list;
    
    //----------------------------------------------------------------------
    
    int main(int argc, char* argv[])
    {
      try
      {
        if (argc < 2)
        {
          std::cerr << "Usage: chat_server <port> [<port> ...]
    ";
          return 1;
        }
    
        boost::asio::io_service io_service;
    
        chat_server_list servers;
        for (int i = 1; i < argc; ++i)
        {
          using namespace std; // For atoi.
          tcp::endpoint endpoint(tcp::v4(), atoi(argv[i]));
          chat_server_ptr server(new chat_server(io_service, endpoint));
          servers.push_back(server);
        }
    
        io_service.run();
      }
      catch (std::exception& e)
      {
        std::cerr << "Exception: " << e.what() << "
    ";
      }
    
      return 0;
    }


    
    
    
    
    
       
    
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  • 原文地址:https://www.cnblogs.com/gcczhongduan/p/5362730.html
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