@Override
    public final void serverCertificateRequested() throws IOException {
        synchronized (ssl) {
            ssl.configureServerCertificate();
        }
    }
Starts a TLS/SSL handshake on this connection using some native methods
from the OpenSSL library. It can negotiate new encryption keys, change
cipher suites, or initiate a new session. The certificate chain is
verified if the correspondent property in java.Security is set. All
listeners are notified at the end of the TLS/SSL handshake.
common/src/main/java/org/conscrypt/ConscryptFileDescriptorSocket.java