Start an asynchronous read. The buffer into which the data will be read must be valid for the lifetime of the asynchronous operation.

template<
    typename MutableBufferSequence,
    typename ReadHandler = default_completion_token_t<executor_type>>
DEDUCED async_read_some(
    const MutableBufferSequence & buffers,
    ReadHandler && handler = default_completion_token_t< executor_type >());

Completion Signature

void(asio::error_code, std::size_t)