<b>ctx</b> or <b>ssl</b> is deleted.</p>

<p>In the case where PSK identity hint is <b>NULL</b>, the server does not send the ServerKeyExchange message to the client.</p>

<p>A server application wishing to use PSKs for TLSv1.2 and below must provide a callback function which is called when the server receives the ClientKeyExchange message from the client. The purpose of the callback function is to validate the received PSK identity and to fetch the pre-shared key used during the connection setup phase. The