ee that they remain valid
                until the handler is called.
              </p></dd>
<dt><span class="term">handler</span></dt>
<dd>
<p>
                The handler to be called when the write operation completes. Copies
                will be made of the handler as required. The equivalent function
                signature of the handler must be:
</p>
<pre class="programlisting">void handler(
  const boost::system::error_code&amp; error, // Result of operation.
  std::size_t bytes_transferred  