Usually when binding a socket to the server, the ip binded could be any of the ips the server keeps including the loopback address, the local area network address, the public Internet address or a preserved address 0.0.0.0.

For loopback address or 127.0.0.1, only local connection to localhost will be recieved. It’s useful in debugging or when using a Reverse Proxy like ngrok.

For the local area networks adress like 192.168.7.7 or public Internet address like 1.2.3.4, only external access to the mechine will be recieved which is most of the server need.

There is an ultimate solution which is a preserved address 0.0.0.0. It includes both three address above and any other unknown addresses. Using it makes sure that all the connections are listen.