Openssl error: SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol

If you see similar errors as below when using openssl to test a https site, it is most likely caused by the SNI that is configured in the reverse proxy or server, like Nginx.

openssl s_client -connect


51089:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:/BuildRoot/Library/Caches/

To make it work, you need to specify the hostname in the command, like this:

openssl s_client -connect -servername



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