If it is to interact with the database, any decent client will do.psql can be called with the sslmode=require option. Making the HTTP request. As soon as you connect to the server, run: ehlo example.com. Use the -servername switch to enable SNI in s_client. Accessing the s_server via openssl s_client. openssl s_client -starttls smtp -connect example.com:25 openssl s_client -starttls smtp -connect example.com:465 openssl s_client -starttls smtp -connect example.com:587. If the connection succeeds then an HTTP command can be given such as "GET /" to retrieve a web page. For more information, see OpenSSL s_client commands man page in the OpenSSL toolkit. $ openssl s_client -connect www.feistyduck.com:443 -servername www.feistyduck.com In order to specify the server name, OpenSSL needs to use a feature of the newer handshake format (the feature is called Server Name Indication [SNI]), and that will force it to abandon the old format. Contribute to openssl/openssl development by creating an account on GitHub. Let's break this down into two parts. SNI is a TLS extension that supports one host or IP address to serve multiple hostnames so that host and IP no longer have to be one to one. Hence in your test the openssl s_client command advertises that is supports NPN but the server turns a blind eye onto ot. openssl s_client sni openssl s_client -connect example.com:443 -servername example.com. The hardest part here is that s_client closes the connection when its stdin gets closed. openssl s_client -cipher ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES256-GCM-SHA384 \ -connect example.com:443 The above list specifies two specific ciphers. First, making the HTTP request, and second, extracting your content from the response. # openssl s_client -connect server:443 -CAfile cert.pem. The handshake still passes OK because the extension appears to be non-essential (or at least considered to be such by openssl) and you get the connected TLS tunnel. # openssl x509 -in cert.pem -out rootcert.crt. To create a full circle, we’ll make sure our s_server is actually working by accessing it via openssl s_client: joris@beanie ~ $ openssl s_client -connect localhost:44330 CONNECTED(00000003) depth=0 C = NL, ST = Utrecht, L = Utrecht, O = Company, OU = Unit, CN = localhos t Convert a root certificate to a form that can be published on a web site for downloading by a browser. To view a complete list of s_client commands in the command line, enter openssl -?. TLS/SSL and crypto library. A group of ciphers can also be passed. Extract a certificate from a server. You will get output like below as reply: Think of it like a zip file for keys & certificates, which includes options to password protect etc. example. openssl s_client -connect ldap-host:636 -showcerts. See man psql.. To connect to an SSL HTTP server the command: openssl s_client -connect servername:443 would typically be used (https uses port 443). If it is to check the SSL certificate (which is why I came across your question), it still doesn't work with s_client as Magnus pointed out 7 years ago. The following table includes some commonly used s_client commands. You didn't specify why you wanted to use s_client.. openssl s_client-connect www. openssl s_client is not a particularly great tool for this, but it can be done. Don’t worry about this unless you need it because some application requires a PKCS12 file or you’re given one that you need to get stuff out of. Ecdhe-Rsa-Aes256-Sha: ECDHE-RSA-AES256-GCM-SHA384 \ -connect example.com:443 the above list specifies two specific ciphers that is NPN! Enter openssl -? GET / '' to retrieve a web page `` GET / '' to a. Example.Com:443 the above list specifies two specific ciphers to enable sni in s_client, any decent client will can... 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