---
syntax: markdown
tags: [tldr, common]
source: https://github.com/tldr-pages/tldr.git
---
# openssl s_client

> OpenSSL command to create TLS client connections.
> More information: <https://docs.openssl.org/master/man1/openssl-s_client/>.

- Display the start and expiry dates for a domain's certificate:

`openssl s_client -connect {{host}}:{{port}} 2>/dev/null | openssl x509 -noout -dates`

- Display the certificate presented by an SSL/TLS server:

`openssl < /dev/null s_client -connect {{host}}:{{port}}`

- Set the Server Name Indicator (SNI) when connecting to the SSL/TLS server:

`openssl s_client -connect {{host}}:{{port}} -servername {{hostname}}`

- Display the complete certificate chain of an HTTPS server:

`openssl < /dev/null s_client -connect {{host}}:443 -showcerts`