What is the address of linux 0.0.0.0

linux 0.0.0.0 means local in the network; 0.0.0.0 is open to the outside world and is a port accessible through service domain name and IP; all server IPs can be matched through 0.0.0.0, if the process listens to 0.0 .0.0, then the client can use this process to access any reachable IP of the server, and when the personal computer is not configured with an IP, it represents the local address.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

What is the address of linux 0.0.0.0?

The 0.0.0.0 and ::

IP addresses in Linux represent that the IP address consists of two parts, net-id and host-id, which are the network number and the host number. .

127.0.0.1

127.0.0.1 belongs to one of the {127,} set. All addresses with network number 127 are called loopback addresses. Therefore, the loopback address is not equivalent to 127.0.0.1. The latter is only a part of the loopback address and is an inclusive relationship. The loopback address loop back.
Compared with 127.0.0.1, localhost has more meaning. localhost is a domain name, not an IP address. The reason why we often think of localhost and 127.0.0.1 as the same is because most of the computers we use point localhost to the address 127.0.0.1.

0.0.0.0

On the server side, match all server IPs through 0.0.0.0. If the process listens to 0.0.0.0, then the client can access any reachable IP of the server. This process can be used.
When the personal computer is not configured with an IP, it indicates the local address.
The router indicates the default route. Really represents local in the network.

Example: When the server binds the port, it is generally bound to 0.0.0.0, so that users can access multiple IPs of this server.

Actual: The server has an internal and external network IP. Generally, the financial system is bound to the internal network IP for internal access only, and the OA is bound to 0.0.0.0 for both internal and external network access.

::

An IPV6 address of all 0s is the same as 0.0.0.0 of IPV4, indicating that it matches multiple IPV6 addresses.

Use double colon "::" to represent a group of 0 or multiple groups of consecutive 0s, but they can only appear once. The leading 0 of each number can be omitted. If the leading number is still 0 after omission, continue.

Linux operation and maintenance need to open the port for viewing. Netstat is to view the port information.

# netstat -nltp

p Check the program hanging on the port

[root@iz2ze5is23zeo1ipvn65aiz ~]# netstat -nltpActive Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      3346/nginx: master  
tcp        0      0 127.0.0.1:8081          0.0.0.0:*               LISTEN      2493/docker-proxy-c 
tcp        0      0 127.0.0.1:8082          0.0.0.0:*               LISTEN      5529/docker-proxy-c 
tcp        0      0 127.0.0.1:8083          0.0.0.0:*               LISTEN      17762/docker-proxy- tcp        0      0 127.0.0.1:8084          0.0.0.0:*               LISTEN      2743/docker-proxy-c 
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2155/sshd

The queried ones include Local, Address, Foregin, Program name

Local: visit Port mode, 0.0.0.0 is an open port to the outside world, indicating that port 80 can be accessed from outside; 127.0.0.1 means that it can only be accessed locally, and this port cannot be accessed from outside;

Address: Port

Foregin Address: open to the outside world, usually 0.0.0.0: *

Program name: This port is used by which program, the program mounts this port

Key words 0.0.0.0 It is a port that is open to the outside world and can be accessed through the service domain name and IP.

127.0.0.1 can only be accessed by the localhost of this machine. This also protects the security of this port.

::: The first two "::" of these three: are the abbreviation of "0:0:0:0:0:0:0:0", which is equivalent to "0.0.0.0" in IPv6. It is all the IPv6 addresses of this machine. The third one: is the separator between IP and port

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