Seconding this; during my B2B support days, this was essential, especially, since as security got a bit crazy, not all systems had telnet installed anymore and you weren't always in a position to install it.

Windows' best equivalent if it doesn't have telnet is from powershell:

Test-NetConnection -Computername [hostname or IP] -Port [some port number]

With the -Port flag, it will try to do a similar connection to a specific port.