This post was published 9 years ago. Due to the rapidly evolving world of technology, some concepts may no longer be applicable.
To verify that SSL caching is on, check the Session-ID across multiple sessions (i.e. resume/reconnect) – they should be the same:
openssl s_client -host HOSTNAME -port 443 -reconnect | grep 'Session-ID:'
The equivalent, using gnutls-cli should be:
gnutls-cli -V -r HOSTNAME |grep 'Session ID'