http://www.cnblogs.com/yyzybb/p/3795532.html
强制关闭
#include
#include
#include
#include
#include
typedef boost::shared_ptr
typedef boost::array
typedef boost::shared_ptr
// 异步读数据回调函数
void on_read(boost::system::error_code ec
, std::size_t len, socket_ptr_t socket_ptr, buffer_ptr_t buffer_ptr)
{
if (ec) // 连接失败, 输出错误码
{
std::cout << "async read error:" << ec.message() << std::endl;
}
}
// 异步写数据回调函数
void on_write(boost::system::error_code ec
, std::size_t len, socket_ptr_t socket_ptr, buffer_ptr_t buffer_ptr)
{
if (ec) // 连接失败, 输出错误码
{
std::cout << "async write error:" << ec.message() << std::endl;
}
}
// 异步连接回调函数
void on_accept(boost::system::error_code ec, socket_ptr_t socket_ptr)
{
if (ec) // 连接失败, 输出错误码
{
std::cout << "async accept error:" << ec.message() << std::endl;
}
else // 连接成功
{
std::cout << "async accept from (" << socket_ptr->remote_endpoint() << ")" << std::endl;
{
buffer_ptr_t buffer_ptr(new buffer_t);
strcpy_s((char*)buffer_ptr->begin(), buffer_t::size(), "abcdefg");
socket_ptr->async_write_some(boost::asio::buffer(buffer_ptr.get(), strlen((char*)buffer_ptr->begin()))
, boost::bind(&on_write, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred
, socket_ptr, buffer_ptr));
}
{
buffer_ptr_t buffer_ptr(new buffer_t);
socket_ptr->async_read_some(boost::asio::buffer(buffer_ptr.get(), buffer_t::size())
, boost::bind(&on_read, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred
, socket_ptr, buffer_ptr));
}
/// 强制关闭连接
socket_ptr->close(ec);
if (ec)
std::cout << "close error:" << ec.message() << std::endl;
}
}
int main()
{
boost::asio::io_service ios; // 创建io_service对象
boost::asio::ip::tcp::endpoint addr(
boost::asio::ip::address::from_string("0.0.0.0"), 12345); // server端地址
boost::asio::ip::tcp::acceptor acceptor(ios, addr, false); // 创建acceptor对象
socket_ptr_t socket_ptr(new boost::asio::ip::tcp::socket(ios));
acceptor.async_accept(*socket_ptr
, boost::bind(&on_accept, boost::asio::placeholders::error, socket_ptr)); // 调用异步accept请求
socket_ptr.reset();
ios.run(); // 调用io_service::run, 等待异步操作结果
std::cout << "press enter key...";
std::cin.get();
return 0;
}
这个例子中，接受到客户端的连接后，立即发起异步读请求和异步写请求，然后立即强制关闭socket。
优雅关闭
#include
#include
#include
#include
#include
typedef boost::shared_ptr
typedef boost::array
typedef boost::shared_ptr
// 异步读数据回调函数
void on_read(boost::system::error_code ec
, std::size_t len, socket_ptr_t socket_ptr, buffer_ptr_t buffer_ptr)
{
static int si = 0;
if (ec) // 连接失败, 输出错误码
{
std::cout << "async read(" << si++ << ") error:" << ec.message() << std::endl;
socket_ptr->shutdown(boost::asio::socket_base::shutdown_receive, ec);
socket_ptr->close(ec);
if (ec)
std::cout << "close error:" << ec.message() << std::endl;
}
else
{ //直到读完了，才进行优雅关闭
std::cout << "read(" << si++ << ") len:" << len << std::endl;
socket_ptr->async_read_some(boost::asio::buffer(buffer_ptr.get(), buffer_t::size())
, boost::bind(&on_read, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred
, socket_ptr, buffer_ptr));
}
}
// 异步写数据回调函数
void on_write(boost::system::error_code ec
, std::size_t len, socket_ptr_t socket_ptr, buffer_ptr_t buffer_ptr)
{
if (ec) // 连接失败, 输出错误码
{
std::cout << "async write error:" << ec.message() << std::endl;
}
else
{
/// 优雅地关闭连接
socket_ptr->shutdown(boost::asio::ip::tcp::socket::shutdown_send, ec);
if (ec)
std::cout << "shutdown send error:" << ec.message() << std::endl;
}
}
// 异步连接回调函数
void on_accept(boost::system::error_code ec, socket_ptr_t socket_ptr)
{
if (ec) // 连接失败, 输出错误码
{
std::cout << "async accept error:" << ec.message() << std::endl;
}
else // 连接成功
{
std::cout << "async accept from (" << socket_ptr->remote_endpoint() << ")" << std::endl;
{
buffer_ptr_t buffer_ptr(new buffer_t);
socket_ptr->async_read_some(boost::asio::buffer(buffer_ptr.get(), buffer_t::size())
, boost::bind(&on_read, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred
, socket_ptr, buffer_ptr));
}
{
buffer_ptr_t buffer_ptr(new buffer_t);
strcpy_s((char*)buffer_ptr->begin(), buffer_t::size(), "abcdefg");
socket_ptr->async_write_some(boost::asio::buffer(buffer_ptr.get(), strlen((char*)buffer_ptr->begin()))
, boost::bind(&on_write, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred
, socket_ptr, buffer_ptr));
}
}
}
int main()
{
boost::asio::io_service ios; // 创建io_service对象
boost::asio::ip::tcp::endpoint addr(
boost::asio::ip::address::from_string("0.0.0.0"), 12345); // server端地址
boost::asio::ip::tcp::acceptor acceptor(ios, addr, false); // 创建acceptor对象
socket_ptr_t socket_ptr(new boost::asio::ip::tcp::socket(ios));
acceptor.async_accept(*socket_ptr
, boost::bind(&on_accept, boost::asio::placeholders::error, socket_ptr)); // 调用异步accept请求
socket_ptr.reset();
ios.run(); // 调用io_service::run, 等待异步操作结果
std::cout << "press enter key...";
std::cin.get();
return 0;
}
在这个例子中，接收到客户端的连接并向客户端发送数据以后，先关闭socket的发送通道，然后等待socket接收缓冲区中的数据全部read出来以后，再关闭socket的接收通道。
此时，socket的接收和发送通道均以关闭，任何进程都无法使用此socket收发数据，但其所占用的系统资源并未释放，底层发送缓冲区中的数据也不保证已全部发出，需要在此之后执行close操作以便释放系统资源。
若在释放系统资源前希望底层发送缓冲区中的数据依然可以发出，则需在socket的linger属性中设置一个等待时间，以便有时间等待发送缓冲区中的数据发送完毕。
但linger中的值绝对不是越大越好，这是因为其原理是操作系统帮忙保留socket的资源以等待其发送缓冲区中的数据发送完毕，如果远端socket的一直未能接收数据便会导致本地socket一直等待下去，这对系统资源是极大的浪费。
因此，在需要处理大量连接的服务端，linger的值一定不可过大。