如何删除一个tcp长连接
有时端口被占用导致服务起不来，发现本机端口被另一个程序使用了。这个时候我们可以使用tcpkill命令来删除这个长连接，让其自动重连换一个端口。然后再启动想启动的服务。
安装tcpkill:
yum -y install dsniff --enablerepo=epel
查询这个连接：
[root@sh5-saas-k8scs1-node-online-167 ~]# netstat -anp | grep 4080
tcp 0 0 10.10.182.167:4080 10.10.182.3:8443 ESTABLISHED 71932/kubelet
unix 2 [ ACC ] STREAM LISTENING 2363408000 61767/containerd /run/containerd/s/e3515d3603c24c9fdf4f6e16c493fe8953ab73538685ca8a52331356a3951649
unix 3 [ ] STREAM CONNECTED 2363408007 61767/containerd
删除连接：
[root@sh5-saas-k8scs1-node-online-167 ~]# tcpkill -9 port 4080
tcpkill: listening on eth0 [port 4080]
10.10.182.167:4080 > 10.10.182.3:8443: R 1598753917:1598753917(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598754418:1598754418(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598755420:1598755420(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598756923:1598756923(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598758927:1598758927(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598761432:1598761432(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598764438:1598764438(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598767945:1598767945(0) win 0
10.10.182.167:4080 > 10.10.182.3:8443: R 1598771953:1598771953(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279911727:1279911727(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279913189:1279913189(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279916113:1279916113(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279920499:1279920499(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279926347:1279926347(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279933657:1279933657(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279942429:1279942429(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279952663:1279952663(0) win 0
10.10.182.3:8443 > 10.10.182.167:4080: R 1279964359:1279964359(0) win 0
使用帮助：
SYNOPSIS
tcpkill [-i interface] [-1...9] expression
DESCRIPTION
tcpkill kills specified in-progress TCP connections (useful for libnids-based applications which require a full TCP 3-whs for TCB creation).
OPTIONS
-i interface Specify the interface to listen on.
-1...9 Specify the degree of brute force to use in killing a connection. Fast connections may require a higher number in order to land a RST in the moving receive window. Default is 3.
expression Specify a tcpdump(8) filter expression to select the connections to kill.
expression与tcpdump的语法一样。
更多参考：
