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Subject JaSFtp issue with GlobalScape Secure Ftp server 2.0
Date   08/15/2006
Message From GlobalScape, we have their Secure-ftp-Server 2.0. If I connect the JaSFtp-Client with ftp-protocol, we can view and transmit, from ftp-server to the client, a folder with 3580 small (2KB) files. But if I connect with sftp, then I d'ont see any files in the same directory. If I reduce the amount of files to 40 files, then I see the files in the directory.

If I install the ftp-client from GlobalScape, then I see all files in the directory.

I evaluate your software and it is a very good tool for our solution. I hope, you can help me. 

Best Regards

Reply1 1) Yes, I did test a folder with about 5500 files and I had no problems. 

2) Does the directory listing fail for the manual SFTP browser only? or a SFTP task to this folder also fails? 

3) Try to view this folder again using the SFTP browser. If the files do not show, look at the Logs menu / Debug log. See if there are any entries there and send that to me.

-- Sincerely, Melvin Desilva Hitek Software


Reply2 Hi Melvin

I was out of the office and today I tried it again. But the problems are the same. I send you the debug Log attached.

Are you using the sftp-Server from GlobalScape or another?

Thanks for your help and Best Regards

May 3, 2005 11:25:00 AMcom.maverick.ssh.SshException: Unknown
channel IO failure: null
at com.maverick.ssh.SubsystemChannel$_B.A(Unknown Source)
at com.maverick.ssh.SubsystemChannel.readMessage(Unknown
at com.maverick.sftp.SftpSubsystemChannel.A(Unknown Source)
at Source)

Reply3 Hi Walter,

I forwarded the error information to my 3rd party api supplier. They have scheduled a few tests against GlobalScape and will get back to me when it is done.

-- Sincerely, Melvin Desilva Hitek Software


Reply4 Hi Walter,

Our 3rd party vendor has responded. Please see below. Though it is a problem with GlobalScape, they will provide an option in their api which they think will fix this issue . Then I will have to include their new api. with a JaSFtp patch update to include this option in the JaSFtp server profiles. All this may take about 1-2 months. So, this fix will only be in JaSFtp Version 6.18-6.20.

Melvin Desilva
Hitek Software


Hi Melvin,

I have taken a look at the Globalscape SFTP server and
located the source of the problem.

Our API is throwing a protocol violation exception because
the server is sending a transport layer packet in the region
of 85000 bytes. The maximum size of transport packets
currently supported by Maverick is 35000 bytes. This figure
is taken from the SSH specification as the recommended figure
for implementations to support. The specification does not
restrict packets to this size and it does allow
implementations to use higher packets although it states that
"larger packets MAY be sent if the version string indicates
that the other party is able to process them".

I think that Globalscape have mis-interpreted the spec here,
there is a seperate channel mechanism on which the SFTP
protocol operates and this does support higher packet sizes,
but these should be broken into smaller packets for the
transport layer.

I am not convinced that Maverick should support higher packet
levels by default since this is the first instance of a
protocol violation of this kind we have seen. I have been
able to resolve the issue by adding an additional field to
the SSH2 context which allows the maximum packet size to be
set. Changing this to a higher value of 100,000 bytes allows
the Maverick API to support the Globalscape server but I
expect that several clients will have issues with their

A new build containing this workaround will be available
within the next couple of weeks.

Reply5 Hi Melvin

Thank you for your answer. Therefore I will wait, until the new version appears.