This event is fired when the protocol requires a client certificate.
This event is fired by TElClientSSLSocket when the negotiated protocol requires a client-side X.509 certificate to be used during session. TElClientSLLSocket fires OnCertificateNeededEx event consequently, until null (Nothing in VB.NET) value is passed as Certificate parameter. This gives the ability to pass a certificate chain to server, not only a single certificate. This event should be handled in the following way: