$ :| openssl s_client -connect host:port -servername host
(ssl/tls version is optional. e.g. -tls1_1)
all options
% openssl s_client --help
unknown option --help
usage: s_client args
-host host - use -connect instead
-port port - use -connect instead
-connect host:port - who to connect to (default is localhost:4433)
-verify_hostname host - check peer certificate matches "host"
-verify_email email - check peer certificate matches "email"
-verify_ip ipaddr - check peer certificate matches "ipaddr"
-verify arg - turn on peer certificate verification
-verify_return_error - return verification errors
-cert arg - certificate file to use, PEM format assumed
-certform arg - certificate format (PEM or DER) PEM default
-key arg - Private key file to use, in cert file if
not specified but cert file is.
-keyform arg - key format (PEM or DER) PEM default
-pass arg - private key file pass phrase source
-CApath arg - PEM format directory of CA's
-CAfile arg - PEM format file of CA's
-no_alt_chains - only ever use the first certificate chain found
-reconnect - Drop and re-make the connection with the same Session-ID
-pause - sleep(1) after each read(2) and write(2) system call
-prexit - print session information even on connection failure
-showcerts - show all certificates in the chain
-debug - extra output
-msg - Show protocol messages
-nbio_test - more ssl protocol testing
-state - print the 'ssl' states
-nbio - Run with non-blocking IO
-crlf - convert LF from terminal into CRLF
-quiet - no s_client output
-ign_eof - ignore input eof (default when -quiet)
-no_ign_eof - don't ignore input eof
-psk_identity arg - PSK identity
-psk arg - PSK in hex (without 0x)
-srpuser user - SRP authentification for 'user'
-srppass arg - password for 'user'
-srp_lateuser - SRP username into second ClientHello message
-srp_moregroups - Tolerate other than the known g N values.
-srp_strength int - minimal length in bits for N (default 1024).
-ssl2 - just use SSLv2
-ssl3 - just use SSLv3
-tls1_2 - just use TLSv1.2
-tls1_1 - just use TLSv1.1
-tls1 - just use TLSv1
-dtls1 - just use DTLSv1
-fallback_scsv - send TLS_FALLBACK_SCSV
-mtu - set the link layer MTU
-no_tls1_2/-no_tls1_1/-no_tls1/-no_ssl3/-no_ssl2 - turn off that protocol
-bugs - Switch on all SSL implementation bug workarounds
-cipher - preferred cipher to use, use the 'openssl ciphers'
command to see what is available
-starttls prot - use the STARTTLS command before starting TLS
for those protocols that support it, where
'prot' defines which one to assume. Currently,
only "smtp", "pop3", "imap", "ftp" and "xmpp"
are supported.
-engine id - Initialise and use the specified engine
-rand file:file:...
-sess_out arg - file to write SSL session to
-sess_in arg - file to read SSL session from
-servername host - Set TLS extension servername in ClientHello
-tlsextdebug - hex dump of all TLS extensions received
-status - request certificate status from server
-no_ticket - disable use of RFC4507bis session tickets
-serverinfo types - send empty ClientHello extensions (comma-separated numbers)
-curves arg - Elliptic curves to advertise (colon-separated list)
-sigalgs arg - Signature algorithms to support (colon-separated list)
-client_sigalgs arg - Signature algorithms to support for client
certificate authentication (colon-separated list)
-nextprotoneg arg - enable NPN extension, considering named protocols supported (comma-separated list)
-alpn arg - enable ALPN extension, considering named protocols supported (comma-separated list)
-legacy_renegotiation - enable use of legacy renegotiation (dangerous)
-use_srtp profiles - Offer SRTP key management with a colon-separated profile list
-keymatexport label - Export keying material using label
-keymatexportlen len - Export len bytes of keying material (default 20)