[JSch-users] SOLVED: SCP will not exit, "session down" error, SSH_MSG_DISCONNECT: 2 Received ieof for nonexistent channel 0

[Manuel B. <man...@gm...>]

Hi

I've encountered many problems when using SCP (copy from and to remote site,
creating directories). Sometimes the program would hang after it had
finished copying, sometimes I got a "session down" exception, sometimes it
just worked fine.

As the root of the problems I have identified the following issues:

Channel.eof() sent an EOF message even if the channel had already been
closed. This in turn resulted in an error from the remote site, which caused
an exception:

  com.jcraft.jsch.JSchException: SSH_MSG_DISCONNECT: 2 Received ieof for
nonexistent channel 0.

The exception was quietly eaten without any error handling.

Additionally, I have removed all two calls of System.gc() because this is
simply not acceptable for many applications, in particular not for a J2EE
application.

Thus, I've made the following modifications to Channel.java and Session.java
(against jsch-0.1.20):


Channel.java:

231d230
<     if (!close) {
243d241
<     }


Session.java:

212c212
< 	      //System.gc();
---
> 	      System.gc();
942d941
<     Exception exception = null;
1192,1193d1190
<       if (socket == null || !socket.isClosed())
<     	exception = e;
1209,1210d1205
<     if (exception != null)
<     	throw new RuntimeException(exception);
1268c1263
<     // System.gc();
---
>     System.gc();


This is a rather simple fix. I think it might be even better to remove most
of the calls of Channel.eof(). I don't think they're necessary after every
read failure.

Session.run() will now throw an exception if something goes wrong. In many
cases, this should help uncover the real cause of a problem.

I hope these modifications can be incorporated into the next release of
Jsch.

Regards
Manuel