FYI the commands below is for Ubuntu OS
sudo /etc/init.d/xinetd status
sudo service telnet status
Restart telnet server:
sudo /etc/init.d/inetd restart
sudo /etc/init.d/openbsd-inetd restart
If neither xinetd, inetd nor openbsd-inetd was found (if all three doesnt exist) then telnet is not installed
Look for telnet solution directory with:
sudo find / -name telnet
apt-cache policy telnet -In ubuntu 16.04 will see that it is installed but if all the above doesnt work then it means it wasnt enabled.
If you dont have inetd deamon wont be able to use the telnet service in your system. When you install telnetd deamon it also installs inetd deamon.
The telnet service is pre-installed in ubuntu but because default ubuntu has no listening port the telnet service is not useful yet.
That also means that one does not need to disable telnet unless the one have installed a telnet daemon