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template< typename ConstBufferSequence, typename WriteToken = default_completion_token_t<executor_type>> DEDUCED async_write_some( const ConstBufferSequence & buffers, WriteToken && token = default_completion_token_t< executor_type >());
This function is used to asynchronously write one or more bytes of data to the stream. It is an initiating function for an asynchronous operation, and always returns immediately.
The data to be written to the stream. 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 completion handler is called.
                The completion
                token that will be used to produce a completion handler, which
                will be called when the write completes. Potential completion tokens
                include use_future,
                use_awaitable,
                yield_context,
                or a function object with the correct completion signature. The function
                signature of the completion handler must be:
              
void handler( const asio::error_code& error, // Result of operation. std::size_t bytes_transferred // Number of bytes written. );
                Regardless of whether the asynchronous operation completes immediately
                or not, the completion handler will not be invoked from within this
                function. On immediate completion, invocation of the handler will
                be performed in a manner equivalent to using post.
              
void(asio::error_code, std::size_t)
          The async_write_some operation may not transmit all of the data to the
          peer. Consider using the async_write function if you need
          to ensure that all data is written before the asynchronous operation completes.
        
          This asynchronous operation supports cancellation for the following cancellation_type
          values:
        
cancellation_type::terminal
            cancellation_type::partial
            
          if they are also supported by the Stream
          type's async_read_some
          and async_write_some operations.