sequence, in both client and server.
</DL>

<P>

<B>-a </B><B></B><I>id</I>, <B>--action </B><B></B><I>id</I> (Set desired action)
<DL COMPACT><DT><DD>
This option specifies the action to be taken by the server upon successful authentication. id must be one of &quot;open&quot; or &quot;close&quot;, to open the knock port or close it, respectively.
</DL>

<P>

<B>-f </B><B></B><I>id</I>, <B>--field </B><B></B><I>id</I> (Set covert channel header field)
<DL COMPACT><DT><DD>
This option specifies the protocol 