openssl Commands

Check which TLS versions are supported on a server :

openssl s_client -connect hostname:port
# to mention specific protocol
openssl s_client -connect hostname:port -tls1
openssl s_client -connect hostname:port -tls1_1
openssl s_client -connect hostname:port -tls1_2
openssl s_client -connect hostname:port -tls1_3

Check server certificate chain :

openssl s_client -connect hostname:port -showcerts