.sslSocketFactory(clientCertificates.sslSocketFactory(), clientCertificates.trustManager())
        .build();

    Call call = client.newCall(new Request.Builder()
        .url(server.url("/"))
        .build());
    Response response = call.execute();
    System.out.println(response.handshake().tlsVersion());
  }

  public static void main(String... args) throws Exception {