[/ / Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com) / / Distributed under the Boost Software License, Version 1.0. (See accompanying / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) /] [section:ResolveHandler Resolve handler requirements] A resolve handler must meet the requirements for a [link boost_asio.reference.Handler handler]. A value `h` of a resolve handler class should work correctly in the expression `h(ec, r)`, where `ec` is an lvalue of type `const error_code` and `r` is an lvalue of type `const ip::basic_resolver_results`. `InternetProtocol` is the template parameter of the [link boost_asio.reference.ip__basic_resolver `ip::basic_resolver<>`] which is used to initiate the asynchronous operation. [endsect]