ss常用分析套接字相关的分析，功能和netstat类似，但比netstat速度更快、功能更多

常用选项：

    -s：打印出统计信息

    -t：打印出tcp相关的信息（默认显示ESTAB相的信息）

    -l：打印出listen相关的连接

    -n：不解析域名、协议、端口号等

    -4：只显示ipv4的连接

用法示例一：显示套接字连接统计信息

[root@admin test]# ss -s
Total: 195 (kernel 264)
TCP:   16 (estab 8, closed 1, orphaned 0, synrecv 0, timewait 0/0), ports 0

Transport Total     IP        IPv6
*	  264       -         -        
RAW	  0         0         0        
UDP	  5         4         1        
TCP	  15        14        1        
INET	  20        18        2        
FRAG	  0         0         0

用法示例二：显示ESTAB相关的连接

 [root@admin test]# ss -tn
State      Recv-Q Send-Q                      Local Address:Port                                     Peer Address:Port              
ESTAB      0      0                          172.17.219.185:53328                                   100.100.30.26:80                 
ESTAB      0      0                          172.17.219.185:2233                                    222.65.55.232:50488              
ESTAB      0      52                         172.17.219.185:2233                                    222.65.55.232:51986              
ESTAB      0      0                          172.17.219.185:2233                                    222.65.55.232:53301              
ESTAB      0      0                          172.17.219.185:33964                                    47.99.169.39:443                
ESTAB      0      0                          172.17.219.185:33960                                    47.99.169.39:443                
ESTAB      0      0                          172.17.219.185:41384                                    47.99.169.39:80                 
ESTAB      0      0                          172.17.219.185:2233                                    222.65.55.232:50612

用法示例三：显示LISTEN相关的连接

[root@admin test]# ss -tnl
State       Recv-Q Send-Q Local Address:Port               Peer Address:Port              
LISTEN      0      128       127.0.0.1:27017                         *:*                  
LISTEN      0      100               *:8009                          *:*                  
LISTEN      0      100               *:8080                          *:*                  
LISTEN      0      128               *:80                            *:*                  
LISTEN      0      128               *:2233                          *:*                  
LISTEN      0      1         127.0.0.1:8005                          *:*                  
LISTEN      0      128              :::8091                         :::*

用法示例四：只显示IPV4相关的连接（排除ipv6）

[root@admin test]# ss -tnl4
State       Recv-Q Send-Q Local Address:Port               Peer Address:Port              
LISTEN      0      128       127.0.0.1:27017                         *:*                  
LISTEN      0      100               *:8009                          *:*                  
LISTEN      0      100               *:8080                          *:*                  
LISTEN      0      128               *:80                            *:*                  
LISTEN      0      128               *:2233                          *:*                  
LISTEN      0      1         127.0.0.1:8005                          *:*

特别注意点：可以通过Recv-Q和Send-Q判断进行的队列状态

当套接字处于连接状态（Established）时，

    Recv-Q 表示套接字缓冲还没有被应用程序取走的字节数（即接收队列长度）。

    而 Send-Q 表示还没有被远端主机确认的字节数（即发送队列长度）。

当套接字处于监听状态（Listening）时，

    Recv-Q ：表示全连接队列当前使用了多少

    Send-Q：表示全连接队列的最大值 

    注：此处接收、发送队列是套接字级的，非系统级的