There have been some reports about, users who are trying to connect to a web server with different ports but getting an error “ERR_UNSAFE_PORT”. This is because of using the unsafe port on your browser, which is not letting you through for security purpose.
For Firefox, you can allow the ports by using the network.security.ports.banned.override. But the updated versions of Firefox doesn’t contain this option in their about:config by default. So you have to add this manually.
- Type “about:config” in the URL
- Now right-click on the list and select New>String
- Type in “network.security.ports.banned.override”
- in value, you can add ports by these methods
1-65535 (All Ports) 87,88,89,1050 (for few ports with commas)