<span class="comment">// our buffer but we don't want to echo those extra received</span>
        <span class="comment">// bytes. `bytes_transferred` will be the number of bytes</span>
        <span class="comment">// up to and including the '\n'. We use `buffers_prefix` so</span>
        <span class="comment">// that extra data is not written.</span>

        <span class="identifier">net</span><span class="special">::</span><span class="identifier">async_write</span><span class="special">(</span><span clas