SFTP problem

jaywilliams · Post by **jaywilliams** » Tue May 22, 2007 9:36 pm

I am using the CoreLITE SFTP to test my SFTP server. I find that the Core SFTP client requests 16K of data with each data retrieve command. My server only sends 4K of data. The Core client appears to use two streams of data each with a different ID. When I retrieve a 60K binary file, the Core client indicates that it successfully retrieves the file, but the data is corrupt. It seems that the first 4k is OK, but the second 4K is set to binary zeros. This pattern continues throughout the file (that is 4K of correct data followed by 4K of zeros). I have tested this with several other SFTP clients and they all correctly retrieve the file.

I know the spec says that the server is supposed to return the amount of data requested by the client, but I believe the client is also supposed to be able to handle a situation where the server does not return the total amount requested.

Any insight on this?

Thanks,
Jay Williams

jaywilliams · Post by **jaywilliams** » Wed May 23, 2007 3:38 pm

Thanks for the reply. I am using CoreFTP Lite version 2. I started with version 1.3 but I uninstalled it and removed any references to CoreFTP in the registry before installing version 2.

The SFTP server I am using is based on the Mocana library. The file is a binary file. I have done a lot of debugging on this problem and I see that the CoreFTP client has two streams active. The first stream requests a 16K block of data starting at offset 0. The second stream requests a 16K block of data starting at offset 16K. My SFTP server returns 4K rather than 16K of data. It appears the two streams get confused by my SFTP server returning less data than requested. The CoreFTP client reports that the file is transferred successfully, but the binary data is incorrect.

Other clients that I have tested successfully retrieve the binary file.

Jay Williams

jaywilliams · Post by **jaywilliams** » Wed May 30, 2007 3:47 pm

I have not seen any reply to my previous response. Have you been able to look into this? The CoreLITE SFTP client reports a successful file transfer of a binary file, but the file is corrupt. It would not be a big problem if the client would at least recognize that the server is not sending the amount of data requested and then fail the transfer. However, the client reports a successful transfer and the received file is corrupt.

Jay Williams