boost.asio简单入坑

网络连接有短连接和长连接。顾名思义，connect之后一直不断开的是长连接，像公司用的数据Route模块；三次握手建立连接后收发一次数据后就断开，断开是四次握手，再次收发数据就再来三次握手建立连接是短连接。每种模式都有优缺点。短连接优点是：如果客户端数量大的话，可以让每个客户轮流请求到数据。缺点：每次连接（三次握手）断开（四次握手）都耗费资源。长连接相对的优点：省资源。缺点：客户量大就会有很多连接不上。各自的用途：长连接适合I／O频繁型的，有很多数据需要传输的，且连接数不需要太多的，像数据Route模块。短连接适合于网站，http服务，比如apache。目前银行接口模块中有bu采用的是短连接，它使用了boost.asio库，接下来简单介绍下如何入坑。

先来个客户端的例子：

#define BOOST_REGEX_NO_LIB
#include <boost/asio.hpp>

void asio_cli1() {
	boost::asio::io_service service;// 在栈中定义类io_service的对象，会自动调用类io_service的构造函数
	// from_string会把字符串格式ip转成硬件识别的地址
	// 类似于sockaddr_in.sin_addr.S_un.S_addr = inet_addr("10.243.141.16");
	boost::asio::ip::tcp::endpoint ep(boost::asio::ip::address::from_string("10.243.141.16"), 9000);
	
	boost::asio::ip::tcp::socket sock(service);// 定义socket对象并调用了构造函数basic_stream_socket(boost::asio::io_service& io_service)
	
	sock.connect(ep);
	size_t len = sock.send(boost::asio::buffer("hello asio\n"));
	sock.close();

}

　　使用上比直接调用系统接口方便很多，还支持跨平台。然后我们可以在buffer中的数据换成各家银行格式的报文就可以模拟银行端的发起请求了。

      服务器端的例子：

#define BOOST_REGEX_NO_LIB
#include <boost/asio.hpp>
using namespace std;

void asio_svr() {
	try {
		boost::asio::io_service io;
		//boost::asio::ip::tcp::endpoint ep(boost::asio::ip::address::from_string("10.253.41.49"), 9000);
		//boost::asio::ip::tcp::acceptor acceptor(io, ep);
		boost::asio::ip::tcp::acceptor acceptor(io, boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), 9000));
		cout<<acceptor.local_endpoint().address()<<endl;
		char buf[1024] = {0};
		for( ; ; ) {
			boost::asio::ip::tcp::socket sock(io);
			acceptor.accept(sock);
			cout<<"cli:"<<sock.remote_endpoint().address()<<endl;
			sock.receive(boost::asio::buffer(buf));
			cout<<buf<<endl;

		}
	} 
	catch (std::exception& e) {
        std::cerr << e.what() << std::endl;
    }

}

　　接下来整个复杂点的，异步模式，IOCP模型（I/O Completion Port）。例子源码来自于官方文档：http://www.boost.org/doc/libs/1_50_0/doc/html/boost_asio/example/allocation/server.cpp

其中1_50_0是版本号，可以修改成自己用的那个，每个版本下都有对应例子的。

#include <cstdlib>
#include <iostream>
#include <boost/aligned_storage.hpp>
#include <boost/array.hpp>
#include <boost/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/asio.hpp>

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

// Class to manage the memory to be used for handler-based custom allocation.
// It contains a single block of memory which may be returned for allocation
// requests. If the memory is in use when an allocation request is made, the
// allocator delegates allocation to the global heap.
class handler_allocator
  : private boost::noncopyable
{
public:
  handler_allocator()
    : in_use_(false)
  {
  }

  void* allocate(std::size_t size)
  {
    if (!in_use_ && size < storage_.size)
    {
      in_use_ = true;
      return storage_.address();
    }
    else
    {
      return ::operator new(size);
    }
  }

  void deallocate(void* pointer)
  {
    if (pointer == storage_.address())
    {
      in_use_ = false;
    }
    else
    {
      ::operator delete(pointer);
    }
  }

private:
  // Storage space used for handler-based custom memory allocation.
  boost::aligned_storage<1024> storage_;

  // Whether the handler-based custom allocation storage has been used.
  bool in_use_;
};

// Wrapper class template for handler objects to allow handler memory
// allocation to be customised. Calls to operator() are forwarded to the
// encapsulated handler.
template <typename Handler>
class custom_alloc_handler
{
public:
  custom_alloc_handler(handler_allocator& a, Handler h)
    : allocator_(a),
      handler_(h)
  {
  }

  template <typename Arg1>
  void operator()(Arg1 arg1)
  {
    handler_(arg1);
  }

  template <typename Arg1, typename Arg2>
  void operator()(Arg1 arg1, Arg2 arg2)
  {
    handler_(arg1, arg2);
  }

  friend void* asio_handler_allocate(std::size_t size,
      custom_alloc_handler<Handler>* this_handler)
  {
    return this_handler->allocator_.allocate(size);
  }

  friend void asio_handler_deallocate(void* pointer, std::size_t /*size*/,
      custom_alloc_handler<Handler>* this_handler)
  {
    this_handler->allocator_.deallocate(pointer);
  }

private:
  handler_allocator& allocator_;
  Handler handler_;
};

// Helper function to wrap a handler object to add custom allocation.
template <typename Handler>
inline custom_alloc_handler<Handler> make_custom_alloc_handler(
    handler_allocator& a, Handler h)
{
  return custom_alloc_handler<Handler>(a, h);
}

class session
  : public boost::enable_shared_from_this<session>
{
public:
  session(boost::asio::io_service& io_service)
    : socket_(io_service)
  {
  }

  tcp::socket& socket()
  {
    return socket_;
  }

  void start()
  {
    socket_.async_read_some(boost::asio::buffer(data_),
        make_custom_alloc_handler(allocator_,
          boost::bind(&session::handle_read,
            shared_from_this(),
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred)));
  }

  void handle_read(const boost::system::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      boost::asio::async_write(socket_,
          boost::asio::buffer(data_, bytes_transferred),
          make_custom_alloc_handler(allocator_,
            boost::bind(&session::handle_write,
              shared_from_this(),
              boost::asio::placeholders::error)));
    }
  }

  void handle_write(const boost::system::error_code& error)
  {
    if (!error)
    {
      socket_.async_read_some(boost::asio::buffer(data_),
          make_custom_alloc_handler(allocator_,
            boost::bind(&session::handle_read,
              shared_from_this(),
              boost::asio::placeholders::error,
              boost::asio::placeholders::bytes_transferred)));
    }
  }

private:
  // The socket used to communicate with the client.
  tcp::socket socket_;

  // Buffer used to store data received from the client.
  boost::array<char, 1024> data_;

  // The allocator to use for handler-based custom memory allocation.
  handler_allocator allocator_;
};

typedef boost::shared_ptr<session> session_ptr;

class server
{
public:
  server(boost::asio::io_service& io_service, short port)
    : io_service_(io_service),
      acceptor_(io_service, tcp::endpoint(tcp::v4(), port))
  {
    session_ptr new_session(new session(io_service_));
    acceptor_.async_accept(new_session->socket(),
        boost::bind(&server::handle_accept, this, new_session,
          boost::asio::placeholders::error));
  }

  void handle_accept(session_ptr new_session,
      const boost::system::error_code& error)
  {
    if (!error)
    {
      new_session->start();
    }

    new_session.reset(new session(io_service_));
    acceptor_.async_accept(new_session->socket(),
        boost::bind(&server::handle_accept, this, new_session,
          boost::asio::placeholders::error));
  }

private:
  boost::asio::io_service& io_service_;
  tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 2)
    {
      std::cerr << "Usage: server <port>\n";
      return 1;
    }

    boost::asio::io_service io_service;

    using namespace std; // For atoi.
    server s(io_service, atoi(argv[1]));

    io_service.run();
  }
  catch (std::exception& e)
  {
    std::cerr << "Exception: " << e.what() << "\n";
  }

  return 0;
}

　　在服务端启动后调试，看到的是在io_service.run()处阻塞了，run函数内调用了while语句，就会一直监听有没有客户端连接。在windows下实现在win_iocp_io_service.ipp文件内。官方给你例子比较复杂，那么来个简单点的，参考了http://blog.csdn.net/zhuky/article/details/5364685

       写一个server类，代码如下：

#include <iostream>
#include <string>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/smart_ptr.hpp>

using namespace boost::asio;
using boost::system::error_code;
using ip::tcp;

// 接收多个客户端连接 然后给客户端发送一条消息
// 如果发送成功就把发送的数据打印出来
class CAsyncService {
public:
    CAsyncService(io_service &iosev, size_t port)
     :m_iosrv(iosev), m_acceptor(iosev, tcp::endpoint(tcp::v4(), port))
    {
    }
    void Start()
    {
        // 开始等待连接（非阻塞）
        boost::shared_ptr<tcp::socket> psocket(new tcp::socket(m_iosrv));
        // 触发的事件只有error_code参数，所以用boost::bind把socket绑定进去
        m_acceptor.async_accept(*psocket,
         boost::bind(&CAsyncService::AcceptHandler, this, psocket, _1)
         );
    }
    // 有客户端连接时AcceptHandler触发
    void AcceptHandler(boost::shared_ptr<tcp::socket> psocket, error_code ec)
     {
        if(ec) return;
        // 继续等待连接
         Start();
        // 显示远程IP
         std::cout << psocket->remote_endpoint().address() << std::endl;
        // 发送信息(非阻塞)
         boost::shared_ptr<std::string> pstr(new std::string("Hello async world!"));
         psocket->async_write_some(buffer(*pstr),
             boost::bind(&CAsyncService::WriteHandler, this, pstr, _1, _2)
             );
     }
    // 异步写操作完成后WriteHandler触发
    void WriteHandler(boost::shared_ptr<std::string> pstr,
         error_code ec, size_t bytes_transferred)
     {
        if(ec)
             std::cout<< "发送失败!" << std::endl;
        else
             std::cout<< *pstr << " 已发送" << std::endl;
     }
private:
     io_service &m_iosrv;
     ip::tcp::acceptor m_acceptor;
};

再简单使用下main函数调用：

int main(int argc, char* argv[])
{
     io_service io;
     CAsyncService ayncserv(io, 9000);
     ayncserv.Start();
     io.run();// 开始等待连接
    return 0;
}