e at most once on completion of the async op. It is executed as if via <code>post(peer_socket-&gt;get_executor())</code>, fully respecting any executor bound to it (via <code>bind_executor()</code>, such as a strand). It shall be passed, in this order, <code>Error_code</code> and a value equal to the one returned by <code>target_payload_blob_func()</code> earlier. The semantics of the first value is identical to that for <code>boost::asio::async_read()</code>. </td></tr>
    <tr><td class="paramname">target