CURL

this tool is usefull to check if a web site is responding or not. The syntax is easy to understand. He can be used for many other protocols than HTTP.

The advantage on a browser, he has no cache. The advantage on ping, who only test the path/connectivity is you can check an application (website, API, etc) on Application level (OSI Layer 7)

Curl is available for many OS, in Linux, Windows, etc

Tutorial is here link and if needed there is the download link

Basic syntax (option -k to bypass the certificate verification/ option -v for verbose ) :

curl -k -v https://it.dbov.net/

Filtered output:
Trying 83.166.138.33…
Connected to it.dbov.net (83.166.138.33) port 443 (#0)
GET / HTTP/2
Host: it.dbov.net
User-Agent: curl/7.58.0
Accept: /
< HTTP/2 200

We can see, the TCP connection to the HTTPS standard port 443 has the status « Connected to »

The HTTP/2 200 mean the the request was successful, so the web site is up :).

HTTP CodesDefinition
200-299success
300-399redirection
400-499client errors
500-599server errors

See the HTTP response code on this link

See the list of TCP port on this link