basic_socket_acceptor::io_control (1 of 2 overloads)

Perform an IO control command on the acceptor.

template<
    typename IoControlCommand>
void io_control(
    IoControlCommand & command);

This function is used to execute an IO control command on the acceptor.

Getting the number of bytes ready to read:

asio::ip::tcp::acceptor acceptor(io_context);
...
asio::ip::tcp::acceptor::non_blocking_io command(true);
socket.io_control(command);