 communication secure. When the returned
future completes the <a href="dart-io/RawSecureSocket-class.html">RawSecureSocket</a> has completed the TLS
handshake. Using this function requires that the other end of the
connection is going to start the TLS handshake.</p>
<p>If the <code>socket</code> already has a subscription, pass the existing
subscription in the <code>subscription</code> parameter. The <a href="dart-io/RawSecureSocket/secureServer.html">secureServer</a>
operation will take over the subscripti