If you are working with some services or ports that your application is using and if you are not receiving information from the server, probably it’s because your firewall is not running or doesn’t have the rules for the port you are using.
# Create a symlink so the service can start with the server
systemctl enable firewalld
# Initialize the firewallD
systemctl start firewalld
# Add a new port in permanent mode to your firewall
firewall-cmd –permanent –add-port=100/tcp
# Finally, check the new port added with