Intermittent SSL protocol error using FTPSImpl (General questions)

by Douglas Handy, Wednesday, October 07, 2009, 17:10 (5525 days ago)

I have used wodFtpDLXcom for years in a project with historically very good success. I use it for FTPSImplicit sessions, and always have.

Recently, one client started frequently getting Data Socket: SSL protocol error when trying to do a transfer. Repeating the attempt will eventually allow it to work. The control connection on port 990 never seems to be the problem -- it is the data port connection.

It doesn't appear to be a firewall blocking part of the port range used for the data connections, as I have seen the errors on the same port where one has worked from the same client location. (I tell the data port from the last 2 figures in the 227 reply text such as 227 Entering Passive Mode (*************,12,54) which would be port 12 * 256 + 54 or 3126).

Searching the forums I found a thread from 2005, but that user solved the problem by using FTPSimplicit instead of FTPSwithdata, and I already use FTPSimpllicit.

The same code has worked for me for a long time, and all sessions are to the same host and the host software has not changed. The host is running Pure-FTPd [TLS] with Glub Tech FTP Wrapper v3.0.4, like it always has.

With the user where I first saw this, it fails more often than it works. And now I am sometimes seeing it with other users, I am sometimes seeing it but so far works more often than it fails.

Any ideas of where to look or what to try?

Doug