Zabbix Agent报“listener failed: zbx_tcp_listen() fatal error: unable to serve on any address”

一台服务器的Zabbix Agent升级后，在Zabbix Server发现Zabbix Agent无法访问。检查Zabbix Agent发现服务停止了，启动Zabbix Agent后，发现服务马上又异常了。遂检查日志发现有下面错误：

26033:20200709:163321.520 Starting Zabbix Agent [xxxx]. Zabbix 5.0.1 (revision c2a0b03480).

26033:20200709:163321.521 **** Enabled features ****

26033:20200709:163321.521 IPv6 support:          YES

26033:20200709:163321.521 TLS support:            NO

26033:20200709:163321.521 **************************

26033:20200709:163321.521 using configuration file: /etc/zabbix/zabbix_agentd.conf

26033:20200709:163321.530 listener failed: zbx_tcp_listen() fatal error: unable to serve on any address [[-]:10050]

26033:20200709:163321.530 Zabbix Agent stopped. Zabbix 5.0.1 (revision c2a0b03480).

检查进程，发现Zabbix Agent的相关进程还在

# ps -ef | grep zabbix

zabbix    4204     1  0 May31 ?        00:09:36 /usr/local/sbin/zabbix_agentd: collector [idle 1 sec]          

zabbix    4205     1  0 May31 ?        00:03:53 /usr/local/sbin/zabbix_agentd: listener #1 [waiting for connection]

zabbix    4206     1  0 May31 ?        00:03:49 /usr/local/sbin/zabbix_agentd: listener #2 [waiting for connection]

zabbix    4207     1  0 May31 ?        00:03:53 /usr/local/sbin/zabbix_agentd: listener #3 [waiting for connection]

zabbix    4208     1  0 May31 ?        00:01:30 /usr/local/sbin/zabbix_agentd: active checks #1 [idle 1 sec]   

root     17881 16153  0 20:52 pts/2    00:00:00 more /tmp/zabbix_agentd.log

root     18036 16153  0 20:54 pts/2    00:00:00 grep zabbix

# /etc/init.d/zabbix-agent stop

Shutting down Zabbix agent: [FAILED]

# /etc/init.d/zabbix-agent status

zabbix_agentd is stopped

# ps -ef | grep zabbix

zabbix    4204     1  0 May31 ?        00:09:36 /usr/local/sbin/zabbix_agentd: collector [idle 1 sec]          

zabbix    4205     1  0 May31 ?        00:03:53 /usr/local/sbin/zabbix_agentd: listener #1 [waiting for connection]

zabbix    4206     1  0 May31 ?        00:03:49 /usr/local/sbin/zabbix_agentd: listener #2 [waiting for connection]

zabbix    4207     1  0 May31 ?        00:03:53 /usr/local/sbin/zabbix_agentd: listener #3 [waiting for connection]

zabbix    4208     1  0 May31 ?        00:01:30 /usr/local/sbin/zabbix_agentd: active checks #1 [idle 1 sec]   

root     17881 16153  0 20:52 pts/2    00:00:00 more /tmp/zabbix_agentd.log

root     18216 16153  0 20:55 pts/2    00:00:00 grep zabbix

# killall -TERM zabbix_agentd

杀掉这些Zabbix Agent进程后，重启Zabbix Agent服务问题解决。结合网上搜索到的相关资料和自己的操作步骤（history查看历史信息）来看，在升级Zabbix前，忘记关闭Zabbix Agent服务（就直接运行rpm -Uvh zabbix-agent-5.0.1-1.el5.x86_64.rpm命令），导致Zabbix的相关进程没法释放。端口被占用，这些进程也无法通过正常的命令关闭。从而出现这个问题。