internal thread of the frontend
          is spawned on the frontend constructor and joined on its destructor (which
          implies that the frontend destruction may block).
        </p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
            The current implementation of the asynchronous sink fro