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>
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// // 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; }