127.0.0.1 vs 0.0.0.0

 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 a non-routable meta-address used to designate an invalid, unknown or non applicable target (a no particular address placeholder).

  In the context of a route entry, it usually means the default route.

  In the context of servers, 0.0.0.0 means "all IPv4 addresses on the local machine". If a host has two ip addresses, 192.168.1.1 and 10.1.2.1, and a server running on the host listens on 0.0.0.0, it will be reachable at both of those IPs.

  0.0.0.0 can also sometimes indicate a broadcast, meaning to all computers on the network. –