同步UDP比较简单，直接看例子：
#include "stdafx.h"
#include "boost/asio.hpp"
#include "boost/shared_ptr.hpp"
#include "boost/thread.hpp"
#include <boost/lexical_cast.hpp>//使用字符串转换功能
using namespace std;
using namespace boost::asio;
#ifdef _MSC_VER
#define _WIN32_WINNT0X0501//避免VC下编译警告
#endif
int udp_server()
{
io_service ios;
ip::udp::endpoint server_ep(ip::udp::v4(),PORT);
ip::udp::socket sock(ios,server_ep);
while(true)
{
char buf[1024];
boost::system::error_code ec;
ip::udp::endpoint remote_ep;//接收远程连接进来的端点
sock.receive_from(buffer(buf),remote_ep,0,ec);
if(ec && ec!=error::message_size)
{
throw boost::system::system_error(ec);
}
cout<<"receive from remote ip:"<<remote_ep.address()<<endl;
cout<<"receive from remote port:"<<remote_ep.port()<<endl;
sock.send_to(buffer("I heard you!"),remote_ep);
}
return 0;
}
int udp_client()
{
io_service ios;
//要发往的服务端点
ip::udp::endpoint send_ep(ip::address::from_string("127.0.0.1"),PORT);
ip::udp::socket sock(ios);
sock.open(ip::udp::v4());
//向服务端发送数据
sock.send_to(buffer("hello"),send_ep);
//接收数据
vector<char> v(1024,0);
ip::udp::endpoint ep;
sock.receive_from(buffer(v),ep);
cout<<"receive from ip:"<<ep.address()<<endl;
cout<<"receive msg:"<<&v[0]<<endl;
}