数据库版本：12c    操作系统版本：redhat6.5

现象描述：监听文件中将ip地址改为域名后，重启提示“地址已经被使用”！，然后查看1521端口被tnslsnr进程占用

处理过程：将tnslsnr进程kill掉后，重启监听成功。

故障疑惑：tnslsnr的作用是什么，为什么会占用1521端口。

附图：
1.[oracle@tyydd-db admin]$ lsnrctl start

LSNRCTL for Linux: Version 12.2.0.1.0 - Production on 08-JUL-2022 11:34:56

Copyright (c) 1991, 2016, Oracle. All rights reserved.

Starting /home/oracle/app/oracle/product/12.2.0/dbhome_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 12.2.0.1.0 - Production
Log messages written to /home/oracle/app/oracle/diag/tnslsnr/tyydd-db/listener/alert/log.xml
Error listening on: (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
TNS-12542: TNS:address already in use
TNS-12560: TNS:protocol adapter error
TNS-00512: Address already in use
Linux Error: 98: Address already in use

Listener failed to start. See the error message(s) above...

[oracle@tyydd-db admin]$ netstat -antup|grep 1521
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 127.0.0.1:1521 0.0.0.0:* LISTEN 25911/tnslsnr

[oracle@tyydd-db admin]$ ps -ef|grep tnslsnr
oracle 20123 19612 0 11:35 pts/1 00:00:00 grep tnslsnr
oracle 25911 1 0 Feb10 ? 00:02:48 /home/oracle/app/oracle/product/12.2.0/dbhome_1/bin/tnslsnr LISTENER -inherit