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
"));
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>
";
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() << "
";
}
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; }