Command to check open ports?

[hux]

Trying to validate whether the right ports are open from Nimble to vCenter. I found this thread from 2016 asking the same question, the answer to which says that 'telnet' works. However, when I log in to the CLI on my Nimble (OS version 5.0.10) and try that it does this:

Nimble OS $ telnet
bash: telnet: command not found

Did 'telnet' get removed and replaced by a different command in later versions of the OS? Or is there maybe an advanced CLI mode I have to switch into in order for that command to be available?