boost官方文檔中聊天程序實例講解
數據包格式chat_message.hpp
<pre name="code" class="cpp"><h3>數據包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)
//實例源於http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio/examples/cpp03_examples.html 文檔中沒有註釋，自己在///開始看的時候也走了點彎路，本文對該源碼寫了詳細的註釋，希望能讓後來者們少走些彎路。
//首先看看數據包的結構：
//數據包分爲兩個部分，首先是報頭佔4bytes，每一byte表示一個數字，也就是最多能表示的出9999，不足在前填0；
// 數據包頭的數字表示數據部分的長度大小。
#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()//將報頭的4字節字符串轉換成數字
{
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()//把數據部分大小編碼成字符串
{
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
聊天客戶端chat_client.cpp
///////////////////////////////////////////////////////////////////////////////////////////////////////
<h3>
</h3><h3>
<span style="white-space:pre-wrap">聊天客戶端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開發文檔中實時聊天程序的客戶端
//實現的大致思路是：在創建的客戶端實例中初始化socket、連接服務器端，並且不斷的進行着異步讀操作（從服務器端讀數據）
//在主線程中，從console中不斷讀取要被髮送的消息，並且把這些消息post至io_service，然後進行異步寫操作
//讀寫socket都是用異步操作
//這種方法不同於分別開一個讀線程，一個寫線程， 它的優勢是線程不會一直等待讀寫數據，在併發數大的情況下通過異步讀寫能提高資源利用率
#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) //使得成員函數能直接使用這些變量
{
boost::asio::async_connect(socket_, endpoint_iterator,
boost::bind(&chat_client::handle_connect, this,
boost::asio::placeholders::error)); //所有的操作都採用異步的方式
}
void write(const chat_message& msg)
{
io_service_.post(boost::bind(&chat_client::do_write, this, msg)); //將消息主動投遞給io_service
}
void close()
{
io_service_.post(boost::bind(&chat_client::do_close, this)); //這個close函數是客戶端要主動終止時調用 do_close函數是從服務器端
//讀數據失敗時調用
}
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), //讀取數據報頭
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()) //分別處理數據報頭和數據部分
{
boost::asio::async_read(socket_,
boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),//讀取數據包數據部分
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()); //輸出消息
std::cout << "\n";
boost::asio::async_read(socket_,
boost::asio::buffer(read_msg_.data(), chat_message::header_length), //在這裏讀取下一個數據包頭
boost::bind(&chat_client::handle_read_header, this,
boost::asio::placeholders::error)); //完成一次讀操作（處理完一個數據包） 進行下一次讀操作
}
else
{
do_close();
}
}
void do_write(chat_message msg)
{
bool write_in_progress = !write_msgs_.empty(); //空的話變量爲false
write_msgs_.push_back(msg); //把要寫的數據push至寫隊列
if (!write_in_progress)//隊列初始爲空 push一個msg後就有一個元素了
{
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)//第一個消息單獨處理，剩下的才更好操作
{
if (!error)
{
write_msgs_.pop_front();//剛纔處理完一個數據 所以要pop一個
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)); //循環處理剩餘的消息
}
}
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>\n";
return 1;
}
boost::asio::io_service io_service;
tcp::resolver resolver(io_service);
tcp::resolver::query query(argv[1], argv[2]); //輸入ip（或域名）和端口號
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() << "\n";
}
return 0;
}
聊天服務器端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)
//
//服務器端程序，首先開啓一個chat_server，用來初始話io_service和chat_room; 服務器每次只開啓一個chat_room，chat_room的作用是 1//.保存用戶信息 2.實現用戶的join和leave 3.保存從每個客戶端接收到的信息 4.將接收到的消息掛到每一個客戶端write_msgs隊尾
//每連接上一個客戶端（socket）就開啓一個新的chat_session 並加入唯一的chat_room chat_session中實現分別對每一個客戶端的異步讀寫//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; //後面需要重載
};
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);
}
//將從某個客戶端收到的消息掛到 每一個客戶端的write_msgs隊尾 具體見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中保存的消息數有限
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來保存用戶信息
enum { max_recent_msgs = 100 };
chat_message_queue recent_msgs_;//用來保存從某個客戶端接收到的信息
};
//----------------------------------------------------------------------
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()//每生成一個新的chat_session都會調用
{
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)); //異步讀客戶端發來的消息
}
void deliver(const chat_message& msg)
{
bool write_in_progress = !write_msgs_.empty();
write_msgs_.push_back(msg); //把room中保存的消息掛到write_msgs隊尾
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)); //服務器端將收到的消息送給所有的客戶端（廣播的方式）
}
}
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) //全局只有一個io_service和一個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(); //每連接上一個socket都會調用
}
private:
boost::asio::io_service& io_service_;
tcp::acceptor acceptor_;
chat_room room_; //chat_room中沒有重載構造函數 所以會直接調用默認構造函數
};
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> ...]\n";
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() << "\n";
}
return 0;
}