drodgers@ubuntu:~$ openssl s_client -connect mqtt.googleapis.com:8883 -showcerts
CONNECTED(00000003)
depth=2 C = US, O = Google Trust Services LLC, CN = GTS Root R1
verify return:1
depth=1 C = US, O = Google Trust Services LLC, CN = GTS CA 1C3
verify return:1
depth=0 CN = mqtt.googleapis.com
verify return:1
---
Certificate chain
 0 s:CN = mqtt.googleapis.com
   i:C = US, O = Google Trust Services LLC, CN = GTS CA 1C3
-----BEGIN CERTIFICATE-----
MIIFeDCCBGCgAwIBAgIQOtwbAaShPv8KAAAAAQivFzANBgkqhkiG9w0BAQsFADBG
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tGj34hzUG2rktJEb
-----END CERTIFICATE-----
 1 s:C = US, O = Google Trust Services LLC, CN = GTS CA 1C3
   i:C = US, O = Google Trust Services LLC, CN = GTS Root R1
-----BEGIN CERTIFICATE-----
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-----END CERTIFICATE-----
 2 s:C = US, O = Google Trust Services LLC, CN = GTS Root R1
   i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA
-----BEGIN CERTIFICATE-----
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-----END CERTIFICATE-----
---
Server certificate
subject=CN = mqtt.googleapis.com

issuer=C = US, O = Google Trust Services LLC, CN = GTS CA 1C3

---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 4720 bytes and written 391 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 2048 bit
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---
read:errno=0