Feature request: being able to use client certificates for network tests (NOT http)

I want to be able to test a TLS service that use server and client
certificates, and the only way seems to be with http, but this is not an
http(s) service.  It would need to be configurable in protocols.cfg or some
other way in hosts.cfg.  I tried pretending it was https and it says 'SSL
error' in the test output.  It doesn't create the sslcert column either, or
I could just disable the https test and still get the certificate
monitoring, which is what I wanted most anyway.

Kind regards,

SebA