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TElSimpleFTPSClient - 425 error

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Cross-platform protocol-independent communication framework for building peer-to-peer and client-server applications and middleware components.
Posted: 05/08/2015 10:44:25
by Christian Thompson (Basic support level)
Joined: 05/08/2015
Posts: 2

Hi, I am running into a 425 error when trying to list a directory using the TEISimpleFTPSClient. I generated this log using a slightly customized version of your sample console application:


2015-05-08T11:15:38 Command: AUTH TLS
2015-05-08T11:15:38 Receive: 234 AUTH TLS successful

2015-05-08T11:15:38 Command: USER ****
2015-05-08T11:15:38 Receive: 331 Password required for ****

2015-05-08T11:15:38 Command: PASS ****
2015-05-08T11:15:38 Receive: 230 User **** logged in

2015-05-08T11:15:38 Command: PBSZ 0
2015-05-08T11:15:39 Receive: 200 PBSZ 0 successful

2015-05-08T11:15:39 Command: PROT P
2015-05-08T11:15:39 Receive: 200 Protection set to Private

2015-05-08T11:15:39 Command: FEAT
2015-05-08T11:15:39 Receive: 211-Features:
MFF modify;UNIX.group;UNIX.mode;
MLST modify*;perm*;size*;type*;unique*;UNIX.group*;UNIX.mode*;UNIX.owner*;
211 End

2015-05-08T11:15:47 Command: TYPE A
2015-05-08T11:15:48 Receive: 200 Type set to A

2015-05-08T11:15:48 Command: PASV
2015-05-08T11:15:48 Receive: 227 Entering Passive Mode (xxx).

2015-05-08T11:15:48 Command: MLSD
2015-05-08T11:15:49 Receive: 150 Opening ASCII mode data connection for MLSD

2015-05-08T11:15:49 Receive: 425 Unable to build data connection: Operation not permitted

2015-05-08T11:15:51 Command: QUIT
2015-05-08T11:15:51 Receive: 221 Goodbye.


This log is almost identical to what FileZilla generates but FileZilla successfully gets the directory listing. The only difference I can see is that FileZilla uses "TYPE I". I tried explicitly setting Client.TransferType to 1, but the client still used "TYPE A".

Looking around on the internet I found that this error might be that the client isn't reusing the SSL session. If this is the case, is there any way to force it to do so?

Posted: 05/08/2015 11:30:00
by Christian Thompson (Basic support level)
Joined: 05/08/2015
Posts: 2

Found it: client.UseSSLSessionResumption
Posted: 05/09/2015 09:35:37
by Eugene Mayevski (EldoS Corp.)

Thank you for contacting us.

The error can have many reasons, from the options that need to be adjusted to network firewall blocking the connection. Binary vs ASCII type should not matter in this case (as per RFC 3659 section 7.2).

It's not clear if your problem is solved by using UseSSLSessionResumption or not. Please let us know.

Sincerely yours
Eugene Mayevski



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