OCSP validation with libnss3

Hi,

I'm trying to validate revocation status of a personal certificate of my
firefox profile using libnss3-tools (Debian Jessie). I found ocspclnt
command:

$ ocspclnt -d . -V "MY CERT NAME" -u c
Verification of certificate "MY CERT NAME" succeeded.

However, it doesn't seem to connect to any OCSP server. It works even if I
shut down my internet connection.

By the way, I don't find any documentation of ocspclnt in:

https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/tools

Regards,

Alfredo