|  | 
        A move accept handler must meet the requirements for a handler.
        A value h of a move accept handler class should work correctly
        in the expression h(ec, s), where ec is an lvalue
        of type const error_code and s is an lvalue of
        the nested type Protocol::socket for the type Protocol
        of the socket class template.
      
A free function as a move accept handler:
void accept_handler(
    const asio::error_code& ec, asio::ip::tcp::socket s)
{
  ...
}
A move accept handler function object:
struct accept_handler
{
  ...
  void operator()(
      const asio::error_code& ec, asio::ip::tcp::socket s)
  {
    ...
  }
  ...
};
A lambda as a move accept handler:
acceptor.async_accept(...,
    [](const asio::error_code& ec, asio::ip::tcp::socket s)
    {
      ...
    });
        A non-static class member function adapted to a move accept handler using
        std::bind():
      
void my_class::accept_handler(
    const asio::error_code& ec, asio::ip::tcp::socket socket)
{
  ...
}
...
asio::async_accept(...,
    std::bind(&my_class::accept_handler,
      this, std::placeholders::_1,
      std::placeholders::_2));