#TIL : Telnet server through SSL or TLS

13 Nov 2018 / by KhanhIceTea

I often use telnet and netcat to debug my TCP server and client. But these tool only support plain connection, mean every data transfer between server and client is unencrypted and unsafe.

So if you want to achieve the same result through secure connection (SSL or TLS), use this command

$ openssl s_client -host example.com -port 443
$ # or short syntax
$ openssl s_client -connect example.com:443

I made a function named telnets in .bash_profile to make it easier to use

function telnets() {
	openssl s_client -host "$1" -port "$2"

then I just type this on bash shell within same syntax of telnet

$ telnets github.com 443

TIP: To hide detail of certificates, add -quiet flag into command

More info, check openssl s_client -h

Sound good ?