A file descriptor does not refer to an open file

[jayli426]

现在用java写了一个ftp下载程序,他总是时不时的报这个错

很多时候都是没有问题,就是偶尔会报

2008-06-24 12:34:22 INFO - Execute the task LJ_ctl_demoCopy.文件下载.
2008-06-24 12:34:22 INFO - Start time for executing the task 文件下载: 2008-06-24 12:34:22
2008-06-24 12:34:22 INFO - Initialize the FTP connection client.

java.net.SocketException: A file descriptor does not refer to an open file.
at java.net.PlainSocketImpl.socketAvailable(Native Method)
at java.net.PlainSocketImpl.available(PlainSocketImpl.java:547)
at java.net.SocketInputStream.available(SocketInputStream.java:246)
at java.io.BufferedInputStream.available(BufferedInputStream.java:386)
at org.apache.commons.net.io.FromNetASCIIInputStream.available(FromNetASCIIInputStream.java:196)
at org.apache.commons.net.io.FromNetASCIIInputStream.read(FromNetASCIIInputStream.java:159)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:229)
at java.io.BufferedInputStream.read(BufferedInputStream.java:246)
at org.apache.commons.net.telnet.TelnetInputStream.__read(TelnetInputStream.java:114)
at org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.java:535)
... 1 more
2008-06-24 12:34:24 INFO - Return status of the task 文件下载: Error

开始以为网络有问题,后来加上一个shell即ftp命令同时下载测试,发现下同一个文件的时候
shell成功下载,但是java的ftp却还是报这个错

难道shell的ftp命令和java 的ftp实现底层是不同的吗?
因为对网络编程不熟悉,很想知道什么时候会报A file descriptor does not refer to an open file
TCP/IP大概也有套错误码来对应把

我尝试将一个文件vi打开,然后用java程序的ftp来下,却还是成功的,
实在不清楚什么时候会出现A file descriptor does not refer to an open file

大虾指教啊