asio C++ library



Start an asynchronous read.

    typename MutableBufferSequence,
    typename ReadHandler>
void-or-deduced async_read_some(
    const MutableBufferSequence & buffers,
    ReadHandler handler);

This function is used to asynchronously read one or more bytes of data from the stream. The function call always returns immediately.



The buffers into which the data will be read. Although the buffers object may be copied as necessary, ownership of the underlying buffers is retained by the caller, which must guarantee that they remain valid until the handler is called.


The handler to be called when the read operation completes. Copies will be made of the handler as required. The equivalent function signature of the handler must be:

void handler(
  const asio::error_code& error, // Result of operation.
  std::size_t bytes_transferred           // Number of bytes read.


The async_read_some operation may not read all of the requested number of bytes. Consider using the async_read function if you need to ensure that the requested amount of data is read before the asynchronous operation completes.