What is the difference between 127.0.0.1 and 0.0.0.0?

binding 127.0.0.1 means listen to loopback interface

Process bound to 127.0.0.1 can only be accessed by other programs from the same machine

binding to 0.0.0.0 means listen to all interfaces ( e.g. all network interfaces connected to the machine )

on Mac 27.0.0.1 /32 is bound to loopback

on Windows 127.0.0.0 /8 is bound to loopback