netstat命令

以前netstat这个命令经常用，但是用的真是稀里糊涂的，写下加深一下印象

常见参数

-a 显示多有的选项，默认是不监听listen的

-t tcp

-u udp

-p 显示建立相关连接的程序名称 

-n 把端口，username，域名 都显示成数组，不会根据ip在定位域名，所以速度会相对快点

-l 仅显示监听

-s 显示每个协议的相关统计

如果是root启用的，普通用户是无法看到程序名称的

[jimmy@xxx ~]$ netstat -altp
(No info could be read for "-p": geteuid()=1000 but you should be root.)
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN      -                   
tcp        0      0 iZ258ugv6ktZ:ssh        220.181.165.11:56273    ESTABLISHED -                   
tcp        0      0 iZ258ugv6ktZ:ssh        220.181.165.10:46172    ESTABLISHED -                   
tcp        0    544 iZ258ugv6ktZ:ssh        220.181.165.7:51149     ESTABLISHED -                   
tcp        0      0 iZ258ugv6ktZ:57580      110.75.102.62:http      ESTABLISHED -  

[root@aliyun ~/]netstat -atlp 
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN      867/sshd            
tcp        0    384 iZ258ugv6ktZ:ssh        220.181.165.11:56273    ESTABLISHED 32210/sshd: root@pt 
tcp        0      0 iZ258ugv6ktZ:ssh        220.181.165.10:46172    ESTABLISHED 32039/sshd: root@pt 
tcp        0      0 iZ258ugv6ktZ:ssh        220.181.165.7:51149     ESTABLISHED 32120/sshd: root@pt 
tcp        0      0 iZ258ugv6ktZ:57580      110.75.102.62:http      ESTABLISHED 11910/AliYunDun

加 -n

[root@aliyun ~/]netstat -atlpn
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      867/sshd            
tcp        0    384 123.56.156.119:22       220.181.165.11:56273    ESTABLISHED 32210/sshd: root@pt 
tcp        0      0 123.56.156.119:22       220.181.165.10:46172    ESTABLISHED 32039/sshd: root@pt 
tcp        0      0 123.56.156.119:22       220.181.165.7:51149     ESTABLISHED 32120/sshd: root@pt 
tcp        0      0 123.56.156.119:57580    110.75.102.62:80        ESTABLISHED 11910/AliYunDun

watch -n 1 -d netstat -ant

-n 周期（s）

-d 高亮显示变动