All ports are allowed to be used and none are blocked by default. To see port as "Open", two main points are important: First, you need to allow it via firewall on the server and second, launch the service which would listen to the specific port.
If communication is not possible over a specific port, please check the firewall rules in your server.
You might need to open a port in your firewall settings first.
- In your Windows server - check your Windows Firewall.
- In your Linux server - check your iptables, firewalld or csf firewall, depending on the firewall you are using.
To find the process or service listening on a particular port in Linux, netstat command can be used with grep command as follows (i.e. port 80):
netstat -tulpn | grep 80