问题描述：应用部署在k8s容器中，有ftp下载功能时报“accept timed out”

如下所示

2022-04-14 20:19:10.392 [pool-6-thread-3] INFO  [10.244.114.7]  *****.ftp.FTPClientAdapter - [,] - Connect to server 172.16.0.44, reply code is 220
2022-04-14 20:19:10.394 [pool-6-thread-3] INFO  [10.244.114.7]  *****.FTPClientAdapter - [,] - Login to server 172.16.0.44, status true, reply code is 230
2022-04-14 20:19:10.396 [pool-6-thread-3] INFO  [10.244.114.7]  ***** .FtpClient - [,] - Change ftp to working dir /hujin
2022-04-14 20:21:10.481 [pool-6-thread-3] ERROR [10.244.114.7]  *****.EmailMessageServiceImpl - [,] - send email error
java.net.SocketTimeoutException: Accept timed out
        at java.net.PlainSocketImpl.socketAccept(Native Method) ~[?:1.8.0_191]
        at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) ~[?:1.8.0_191]
        at java.net.ServerSocket.implAccept(ServerSocket.java:545) ~[?:1.8.0_191]
        at java.net.ServerSocket.accept(ServerSocket.java:513) ~[?:1.8.0_191]
        at org.apache.commons.net.ftp.FTPClient._openDataConnection_(FTPClient.java:806) ~[commons-net-3.8.0.jar!/:3.8.0]
        at org.apache.commons.net.ftp.FTPClient._retrieveFile(FTPClient.java:971) ~[commons-net-3.8.0.jar!/:3.8.0]
        at org.apache.commons.net.ftp.FTPClient.retrieveFile(FTPClient.java:3308) ~[commons-net-3.8.0.jar!/:3.8.0]

从上面可以看出ftp登录以及切换目录都成功了，但是调用ftp的retrieveFile方法就下载不下来文件。

测试环境能正常下载，而容器化部署报错。

解决方案：其实这个问题很容易解决

原先ftp client创建是被动模式导致在容器化部署的环境ftp下载文件失败

ftpClient.enterLocalPassiveMode()

上述代码即可解决该问题。

有兴趣可以了解下ftp主被动模式

附上别人的链接ftp主动模式与被动模式_brother小果的博客-CSDN博客_ftp主动和被动模式