tlsSocket.getX509Certificate()
将本地证书作为 <X509Certificate> 对象返回。
🌐 Returns the local certificate as an <X509Certificate> object.
如果没有本地证书,或者套接字已被销毁,将返回 undefined。
🌐 If there is no local certificate, or the socket has been destroyed,
undefined will be returned.