Earlier many system admins were using telnet to check if a port is open on remote machine. But, because of security concerns telnet is now not recommended to be installed on most linux boxes.
But hey we still need to check the remote port. This is part of normal troubleshooting in a linux admin’s life.
So, instead of using telnet you can use nc. netcat or nc is a simple tool which is generally installed by default in linux distributions or you can install it with instructions below.