Linux服务器当前各种TCP网络连接状态的统计

例如服务器上的TCP网络连接状态显示如下：
[root@huzhenwei ~]# netstat -nat

Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 0.0.0.0:10050 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:554 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:1935 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:3001 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:1947 0.0.0.0:* LISTEN

tcp 0 0 172.16.6.93:80 172.16.6.93:51201 ESTABLISHED

tcp 0 0 172.16.6.93:80 172.16.6.93:51202 ESTABLISHED

tcp 0 0 172.16.6.93:10050 172.16.3.112:32769 TIME_WAIT

tcp 0 0 172.16.6.93:51201 172.16.6.93:80 ESTABLISHED

tcp 0 0 172.16.6.93:51202 172.16.6.93:80 ESTABLISHED

tcp 0 1 172.16.6.93:53276 172.16.3.162:8080 SYN_SENT

tcp 0 0 :::22 :::* LISTEN

tcp 0 844 ::ffff:172.16.6.93:22 ::ffff:172.16.1.36:56495 ESTABLISHED

统计命令和计算结果如下：
[root@huzhenwei ~]# netstat -nat | awk 'FNR>2{print $NF}' | sort | uniq -c

5 ESTABLISHED

9 LISTEN

1 TIME_WAIT

参数说明：
netstat -nat 参数t表示只列出tcp连接

awk 'FNR>2{print $NF}'
FNR表示这条记录的行号，NF表示这一条记录中的字段总数

TCP连接状态的定义：
ESTABLISHED

The socket has an established connection.

SYN_SENT

The socket is actively attempting to establish a connection.

SYN_RECV

A connection request has been received from the network.

FIN_WAIT1

The socket is closed, and the connection is shutting down.

FIN_WAIT2

Connection is closed, and the socket is waiting for a shutdown from the remote end.

TIME_WAIT

The socket is waiting after close to handle packets still in the network.

CLOSED The socket is not being used.

CLOSE_WAIT

The remote end has shut down, waiting for the socket to close.

LAST_ACK

The remote end has shut down, and the socket is closed. Waiting for acknowledgement.

LISTEN The socket is listening for incoming connections. Such sockets are not included in the output

unless you specify the --listening (-l) or --all (-a) option.

CLOSING

Both sockets are shut down but we still don’t have all our data sent.

UNKNOWN

The state of the socket is unknown.