You can easily test if the port is open or closed on a remote server in Windows or Linux via telnet client:
(This command is same for Linux and Windows machine, as long as you have the telnet client installed in your machine)
[[email protected] /]# telnet simplenotes.io 80
Connected to simplenotes.io.
Escape character is '^]'.
In Linux you may also use netcat command or known as “nc”, you can simply install this by typing the following in CentOS terminal:
yum install nc
To test the port you can type:
[[email protected] /]# nc -v -z simplenotes.io 80
Connection to simplenotes.io 80 port [tcp/http] succeeded!
[[email protected] /]# nc -v -z simplenotes.io 81
nc: connect to simplenotes.io port 81 (tcp) failed: No route to host