boost在1.35版本之后终于加入了网络库asio。春节期间终于得闲能够一窥究竟，同时将boost.asio和知名的ACE框架做一下比较。
asio的名字突出了异步I/O的能力，从asio的文档中看到它使用了和ACE Proactor框架中相似的Proactor模式。考试大提示CSDN上也有很多网友也写了很多关于异步I/O的好文章，但是还是决定从同步I/O开始。尽管阻塞I/O不是那么酷那么绚丽但是在网络编程中它和异步I/O一样重要。
下面是一个简单的同步I/O的例子，使用的是锁步(lock-step)方式的通讯。
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#include <string>
#include "boost/asio.hpp"
#include "boost/lexical_cast.hpp"
using namespace std;
using namespace boost;
using boost::asio::ip::tcp;
using boost::asio::io_service;
class Client
{
public:
Client (const string & hostname, unsigned short port);
virtual ~Client ();
// methods
virtual void send (const string & message);
virtual string recv ();
virtual void close ();
private:
io_service * io_service_;
tcp::socket * socket_;
};
Client::Client (const string & hostname, unsigned short port)
{
io_service_ = new io_service();
socket_ = new tcp::socket(*io_service_);
tcp::resolver resolver(*io_service_);
tcp::resolver::query query(hostname, boost::lexical_cast<string, unsigned short>(port));
boost::system::error_code ec;
tcp::resolver::iterator iter = resolver.resolve(query, ec);
tcp::resolver::iterator end;
// pick the first endpoint
if (iter != end && ec == 0)
{
tcp::endpoint endpoint = *iter;
std::cout << "Connecting to: " << endpoint << std::endl;
socket_->connect(endpoint, ec);
if (ec)
{
std::cerr << "Error: " << ec << std::endl;
throw ec;
}
}
}
Client::~Client ()
{
delete socket_;
delete io_service_;
}
void Client::send (const string & message)
{
boost::asio::const_buffers_1 request(message.data(), message.size());
socket_->send(request);
}
string Client::recv ()
{
char response[128];
size_t num = socket_->receive(boost::asio::buffer(response));
if (num > 0)
{
return string (response, num);
}
return "";
}
void Client::close ()
{
socket_->close();
}
int _tmain(int argc, _TCHAR* argv[])
{
Client client ("localhost", 2009);
std::cout << client.recv() << endl;
string request;
do
{
std::cout << "Request: ";
std::cin >> request;
if (request == "q")
break;
client.send (request);
std::cout << "Response: " << client.recv() << endl;
}
while (true);
client.close();
return 0;
}
责任编辑：cyth
