netstat

1. 列出所有连接

   $ netstat -a
   

2. 禁用反向域名解析，加快查询下速度

   $ netstat -ant
   Active Internet connections (servers and established)
   Proto Recv-Q Send-Q Local Address           Foreign Address         State      
   tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN     
   tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN     
   tcp        0      0 192.168.1.2:49058       173.255.230.5:80        ESTABLISHED
   tcp        0      0 192.168.1.2:33324       173.194.36.117:443      ESTABLISHED
   tcp6       0      0 ::1:631                 :::*                    LISTEN
   

3. 只列出监听中的连接

   $ netstat -tnl
   Active Internet connections (only servers)
   Proto Recv-Q Send-Q Local Address           Foreign Address         State      
   tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN     
   tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN     
   tcp6       0      0 ::1:631                 :::*                    LISTEN