一、获取TCP连接数相关方法
方法一：
[root@host-47-98-97-124 scripts]# netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}'
LISTEN 6
ESTABLISHED 64
TIME_WAIT 100

方法二：
[root@host-47-98-97-124 scripts]# ss -ant | awk 'NR>1 {a[$1]++} END {for (b in a) print b,a[b]}'
LISTEN 6
ESTAB 64
TIME-WAIT 100

netstat是遍历/proc下面每个PID目录，ss直接读/proc/net下面的统计信息。所以ss执行的时候消耗资源以及消耗的时间都比netstat少很多。

二、TCP状态信息描述
ESTABLISHED socket已经建立连接
CLOSED socket没有被使用，无连接
CLOSING 服务器端和客户端都同时关闭连接
CLOSE_WAIT 等待关闭连接
TIME_WAIT 表示收到了对方的FIN报文，并发送出了ACK报文，等待2MSL后就可回到CLOSED状态
LAST_ACK 远端关闭，当前socket被动关闭后发送FIN报文，等待对方ACK报文
LISTEN 监听状态
SYN_RECV 接收到SYN报文
SYN_SENT 已经发送SYN报文
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.

编写tcp状态监控脚本

#!/bin/bash

if [ $# -ne 1 ];then
echo "Follow the script name with an argument "
fi

case $1 in 

established)   #socket已经建立连接 
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | grep -w ESTABLISHED | cut -d " "  -f 2`
    echo $result
    ;;

listen)        #监听状态  
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | grep -w LISTEN | cut -d " "  -f 2`
    echo $result
    ;;

timewait)     #表示收到了对方的FIN报文，并发送出了ACK报文，等待2MSL后就可回到CLOSED状态 
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | grep -w TIME_WAIT | cut -d " "  -f 2`
    echo $result
    ;;

closed)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/CLOSED/{print $2}'`
    echo $result
    ;;

closewait)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/CLOSE_WAIT/{print $2}'`
    if [ "$result" == "" ];then
           echo 0
    else
       echo $result
    fi
    ;;

closing)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/CLOSING/{print $2}'`
    echo $result
    ;;

finwait1)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/FIN_WAIT1/{print $2}'`
    echo $result
    ;;

finwait2)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/FIN_WAIT2/{print $2}'`
    echo $result
    ;;

lastack)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/LAST_ACK /{print $2}'`
    echo $result
    ;;

synrecv)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/SYN_RECV/{print $2}'`
    echo $result
    ;;

synsent)
    result=`netstat -an | awk '/^tcp/ {a[$NF]++} END {for (b in a) print b,a[b]}' | awk '/SYN_SENT/{print $2}'`
    echo $result
    ;;  

    *)
      echo -e "\e[033mUsage: sh  $0 [closed|closing|closewait|synrecv|synsent|finwait1|finwait2|listen|established|lastack|timewait]\e[0m"

esac

#!/bin/bash

if [ $# -ne 1 ];then
echo "Follow the script name with an argument "
fi

case $1 in 

LISTEN)
    result=`ss -ant | awk 'NR>1 {a[$1]++} END {for (b in a) print b,a[b]}' | awk '/LISTEN/{print $2}'`
    if [ "$result" == "" ];then
           echo 0
    else
       echo $result
    fi
    ;;

ESTAB)
    result=`ss -ant | awk 'NR>1 {a[$1]++} END {for (b in a) print b,a[b]}' | awk '/ESTAB/{print $2}'`
    if [ "$result" == "" ];then
           echo 0
    else
       echo $result
    fi
    ;;

CLOSE-WAIT)
    result=`ss -ant | awk 'NR>1 {a[$1]++} END {for (b in a) print b,a[b]}' | awk '/CLOSE-WAIT/{print $2}'`
    if [ "$result" == "" ];then
           echo 0
    else
       echo $result
    fi
    ;;

TIME-WAIT)
    result=`ss -ant | awk 'NR>1 {a[$1]++} END {for (b in a) print b,a[b]}' | awk '/TIME-WAIT/{print $2}'`
    if [ "$result" == "" ];then
           echo 0
    else
       echo $result
    fi
    ;;

esac