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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 data to the stream socket. It is an initiating function for an asynchronous operation, and always returns immediately.
One or more data buffers to be written to the socket. Although the buffers object may be copied as necessary, ownership of the underlying memory blocks 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 write 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.
        
          To write a single data buffer use the buffer function as follows:
        
socket.async_write_some(asio::buffer(data, size), handler);
          See the buffer
          documentation for information on writing multiple buffers in one go, and
          how to use it with arrays, boost::array or std::vector.
        
          On POSIX or Windows operating systems, this asynchronous operation supports
          cancellation for the following cancellation_type values:
        
cancellation_type::terminal
            cancellation_type::partial
            cancellation_type::total