How to check the availability of ports for a specific service?

Question

Computer networks

In general, you need to check the availability of a certain address and two ports, 80 and 443. It is from my address, on that service, that they are definitely open.
How can this be checked? Telnet? o [address] 443/80 ?
Tell me please.

Answer 1

If TCP, then telnet will do. But nmap is better.

Answer 2

$ telnet ya.ru 80
Trying 87.250.250.242...
Connected to ya.ru.
Escape character is '^]'.
^CConnection closed by foreign host.
$ nmap -p 80,443 ya.ru
Starting Nmap 7.01 ( https://nmap.org ) at 2018-12-03 09:17 MSK
Nmap scan report for ya.ru (87.250.250.242)
Host is up (0.018s latency) .
Other addresses for ya.ru (not scanned): 2a02:6b8::2:242
PORT STATE SERVICE
80/tcp open http
443/tcp open https
Nmap done: 1 IP address (1 host up) scanned in 0.07 seconds