A wait handler must meet the requirements for a handler. A value h of a wait handler class should work correctly in the expression h(ec), where ec is an lvalue of type const error_code.

Examples

A free function as a wait handler:

void wait_handler(
    const asio::error_code& ec)
{
  ...
}

A wait handler function object:

struct wait_handler
{
  ...
  void operator()(
      const asio::error_code& ec)
  {
    ...
  }
  ...
};

A lambda as a wait handler:

socket.async_wait(...,
    [](const asio::error_code& ec)
    {
      ...
    });

A non-static class member function adapted to a wait handler using std::bind():

void my_class::wait_handler(
    const asio::error_code& ec)
{
  ...
}
...
socket.async_wait(...,
    std::bind(&my_class::wait_handler,
      this, std::placeholders::_1));

A non-static class member function adapted to a wait handler using boost::bind():

void my_class::wait_handler(
    const asio::error_code& ec)
{
  ...
}
...
socket.async_wait(...,
    boost::bind(&my_class::wait_handler,
      this, asio::placeholders::error));