iding an SSL (TLS)
client certificate, set the optional parameters requestClientCertificate or
requireClientCertificate to true.  Require implies request, so one doesn't
need to specify both.  To check whether a client certificate was received,
check SecureSocket.peerCertificate after connecting.  If no certificate
was received, the result will be null.</p>
<p><code>supportedProtocols</code> is an optional list of protocols (in decreasing
order of preference) to use during the ALPN protocol negotiation with