OpenSSL commands 

To get the server certificates that are used during the HTTPS connection initiation, run the following commands:

openssl s_client -showcerts -connect <hostname>:<port> < /dev/null > <outfile.txt>
openssl x509 -inform PEM -in <outfile.txt> -text -out <certificatefile.txt>

openssl s_client -showcerts -connect www.google.com:443 < /dev/null > outfile
openssl x509 -inform PEM -in outfile -text -out cdata