ORA-12547:TNS:丢失连接

用sqlplus连接远程的数据库(不是同一网段)，报ORA-12547:TNS:丢失连接。查看数据库的监听日志，发现错误：
Thu Apr 18 18:30:23 2019
18-APR-2019 18:30:23 * * (ADDRESS=(PROTOCOL=tcp)(HOST=111.25.129.234)(PORT=11236)) * establish * * 12525
TNS-12525: TNS:listener has not received client’s request in time allowed
TNS-12535: TNS:operation timed out
TNS-12606: TNS: Application timeout occurred

查看metlink的解释：
metalink:
Changes
Value of idle timer was recently changed at firewall level.
Cause
Firewall closes ports not allowing the 3-way handshake to complete at TCP level.
Solution
Increase the firewall’s idle timeout interval.

检查是公司防火墙阻止导致，配置111.25.129.234成白名单放行即可。