/samp>&rsquo;</dt>
<dd><p>A file containing a certificate to use in the handshake with the peer.
(When operating as server, in listen mode, this is more often required
by the peer, while client certificates only are mandated in certain
setups.)
</p>
</dd>
<dt>&lsquo;<samp>key_file, key=<var>filename</var></samp>&rsquo;</dt>
<dd><p>A file containing the private key for the certificate.
</p>
</dd>
<dt>&lsquo;<samp>listen=<var>1|0</var></samp>&rsquo;</dt>
<dd><p>If enabled, listen for connections on the provid