PuTTY is using the telnet protocol in that link.
Telnet has been a built-in component of Windows at least since Windows 3.1.1.
From that point through Windows XP, Telnet was enabled by default. Since it’s an insecure protocol, and will pass any provided credentials in clear text, it was disabled by default starting with Windows 7. It can easily be added back in (though not necessarily recommended) to Win7, Win8, Win10, and Win11 (and all comparable server versions since Server 2008) by using the “Add/Remove Components” tool in Windows. Note that there are separate options for enabling telnet client and telnet server. You would want the client option.
Once enabled, the “port exploring” described at the link could be accomplished by just opening a command prompt and typing
telnet <server name or IP> port
telnet 192.168.0.42 30003
This would stream any activity at that port to your console window (stdout). End the connection by hitting ctrl+c
If you wanted to save the output to a file, just add a greater-than symbol and a file name
telnet 192.168.0.42 30003 > PortOutput.txt
Or use a double greater-than to append the output to an existing file: (and create that file if it doesn’t exist)
telnet 192.168.0.42 30003 >> PortOutput.txt
Nice thing about not using PuTTY is that you don’t have to create a “connection”, and sift through a bunch of options that have a purpose but mostly aren’t required for simple things like this.
Interestingly, telnet was completely removed from MacOS some time ago, and can only be utilized by installing or compiling 3rd party software (there is even a port of PuTTY for Mac).