How to obtain the certificates for a remote server

Knowledge Base - How To

Friday, January 23, 2026

Overview:

Solution Steps:

To read the certificates as an output for a site like “server.com” reachable on port 123, run

$ openssl s_client -showcerts -connect server.com:123 </dev/null 2>/dev/null

There could be more than one certificates that will show up like

-----BEGIN CERTIFICATE-----
MIIFYjCCBEqgAwIBAgIQd70NbNs2+RrqIQ/E8FjTDTANBgkqhkiG9w0BAQsFADBX
.

.
d0lIKO2d1xozclOzgjXPYovJJIultzkMu34qQb9Sz/yilrbCgj8=
-----END CERTIFICATE-----

i.e.

$ openssl s_client -showcerts -connect google.com:443 </dev/null 2>/dev/null