localhost

What are all these differences? And what does “local” really mean?

https://stackoverflow.com/questions/20778771/what-is-the-difference-between-0-0-0-0-127-0-0-1-and-localhost

https://superuser.com/questions/949428/whats-the-difference-between-127-0-0-1-and-0-0-0-0

• 127.0.0.1 is the loopback address (also known as localhost)
• 0.0.0.0 is commonly used as a non-routable meta-address used to designate an invalid, unknown or non applicable target (a no particular address placeholder).

127.0.0.1 is a “fake” network adapter that can only communicate within the same host.

• “localhost” is normally the hostname for the 127.0.0.1 IP address.
• usually set in /etc/hosts (or the Windows equivalent named “hosts” somewhere under %WINDIR%)
• If you do ping localhost, it resolves to 127.0.0.1

When a server is told to listen on 0.0.0.0 that means “listen on every available network interface”.

• The loopback adapter with IP address 127.0.0.1 from the perspective of the server process looks just like any other network adapter on the machine, so a server told to listen on 0.0.0.0 will accept connections on that interface too.