Linux程序监听网卡端口的时候会有各种缩写,其中有一种叫做冒号端口的写法。

现象

首先,我们看一段netstat的输出:

[email protected]:~# netstat -tunlp 
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:25672           0.0.0.0:*               LISTEN      639/beam.smp        
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      895/mysqld          
tcp        0      0 0.0.0.0:6379            0.0.0.0:*               LISTEN      16717/redis-server  
tcp        0      0 127.0.0.1:2379          0.0.0.0:*               LISTEN      581/etcd            
tcp        0      0 127.0.0.1:2380          0.0.0.0:*               LISTEN      581/etcd            
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      737/nginx: master p 
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      627/sshd            
tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      766/postgres        
tcp        0      0 127.0.0.1:8088          0.0.0.0:*               LISTEN      604/influxd         
tcp6       0      0 :::45473                :::*                    LISTEN      504/java            
tcp6       0      0 :::9090                 :::*                    LISTEN      601/prometheus      
tcp6       0      0 :::2181                 :::*                    LISTEN      504/java            
tcp6       0      0 :::5672                 :::*                    LISTEN      639/beam.smp        
tcp6       0      0 ::1:6379                :::*                    LISTEN      16717/redis-server  
tcp6       0      0 :::9100                 :::*                    LISTEN      595/prometheus-node 
tcp6       0      0 :::4369                 :::*                    LISTEN      1/init              
tcp6       0      0 :::8086                 :::*                    LISTEN      604/influxd         
tcp6       0      0 :::22                   :::*                    LISTEN      627/sshd            
tcp6       0      0 ::1:5432                :::*                    LISTEN      766/postgres        
udp        0      0 0.0.0.0:68              0.0.0.0:*                           533/dhclient        
udp        0      0 0.0.0.0:51591           0.0.0.0:*                           639/beam.smp 

这段输出中,Local Address一栏,出现了各种表示法,0.0.0.0:25672:::45473::1:5432,这几种写法,其中0.0.0.0这种写法很明显是监听所有网卡,后面两种则叫做冒号端口。

解释

冒号端口是ipv6才有的表示法

:::表示ipv6的所有网卡,类比ipv4的0.0.0.0

::1表示ipv6的本地回环网卡,类比ipv4中的127.0.0.1