Can't access localhost via IP address
If you can access a server running on your own machine via
localhost) but not via the computer's ip address, this means that the server software is configured to listen on the localhost interface only. This is a configuration item and to avoid exposing a potentially unsecure server many server programs come preconfigured to listen on localhost only. That way you can safely test locally before exposing the server.
0.0.0.0 means "listen on all interfaces present on this computer" which is convenient, but may cause security issues if the machine has multiple interfaces.