Can no longer connect to server

[bluespy]

Since I updated to the latest version (3.13.1), I could no longer connect to one of my FTP servers using sftp. There were no changes on the server side, and nothing out of the blue seems to happening.

This issue was also in the 3.13 version, though I did not report the bug at the time. The last working version that was able to connect to the server is 3.12.0.2.

Here is log from filezilla:

2015-08-30 15:30:13 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:13 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:13 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:13 16608 1 Error: Network error: Software caused connection abort
2015-08-30 15:30:13 16608 1 Error: Could not connect to server
2015-08-30 15:30:13 16608 1 Status: Waiting to retry...
2015-08-30 15:30:18 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:18 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:18 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:18 16608 1 Error: Network error: Software caused connection abort
2015-08-30 15:30:18 16608 1 Error: Could not connect to server
2015-08-30 15:30:18 16608 1 Status: Waiting to retry...
2015-08-30 15:30:23 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:23 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:23 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:23 16608 1 Error: Network error: Connection reset by peer
2015-08-30 15:30:23 16608 1 Error: Could not connect to server
2015-08-30 15:30:23 16608 1 Status: Waiting to retry...
2015-08-30 15:30:28 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:28 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:28 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:28 16608 1 Error: Network error: Software caused connection abort
2015-08-30 15:30:28 16608 1 Error: Could not connect to server
2015-08-30 15:30:28 16608 1 Status: Waiting to retry...
2015-08-30 15:30:33 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:33 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:33 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:34 16608 1 Error: Network error: Software caused connection abort
2015-08-30 15:30:34 16608 1 Error: Could not connect to server
2015-08-30 15:30:34 16608 1 Status: Waiting to retry...
2015-08-30 15:30:39 16608 1 Status: Connecting to 139.255.47.238...
2015-08-30 15:30:39 16608 1 Response: fzSftp started, protocol_version=3
2015-08-30 15:30:39 16608 1 Command: open "user@139.255.47.238" 22
2015-08-30 15:30:40 16608 1 Error: Connection attempt interrupted by user

[Alexander Schuch]

Can you set your log level to "debug" and post *one* connection attempt?

[bluespy]

Log with debug status on, as below:

Status: Connecting to 139.255.47.238...
Trace: Going to execute C:\Program Files (x86)\FileZilla FTP Client\fzsftp.exe
Response: fzSftp started, protocol_version=3
Trace: CSftpControlSocket::ConnectParseResponse(fzSftp started, protocol_version=3)
Trace: CSftpControlSocket::SendNextCommand()
Trace: CSftpControlSocket::ConnectSend()
Command: open "user@139.255.47.238" 22
Trace: Looking up host "139.255.47.238"
Trace: Connecting to 139.255.47.238 port 22
Trace: We claim version: SSH-2.0-PuTTY_Local:_Aug_24_2015_15:56:07
Trace: Server version: SSH-2.0-CoreFTP-0.3.2
Trace: Using SSH protocol version 2
Trace: Network error: Software caused connection abort
Error: Network error: Software caused connection abort
Trace: CControlSocket::DoClose(64)
Trace: CSftpControlSocket::ResetOperation(66)
Trace: CControlSocket::ResetOperation(66)
Error: Could not connect to server
Trace: CFileZillaEnginePrivate::ResetOperation(66)
Status: Waiting to retry...
Trace: CControlSocket::DoClose(64)
Trace: CControlSocket::DoClose(64)
Status: Connecting to 139.255.47.238...
Trace: Going to execute C:\Program Files (x86)\FileZilla FTP Client\fzsftp.exe
Response: fzSftp started, protocol_version=3
Trace: CSftpControlSocket::ConnectParseResponse(fzSftp started, protocol_version=3)
Trace: CSftpControlSocket::SendNextCommand()
Trace: CSftpControlSocket::ConnectSend()
Command: open "user@139.255.47.238" 22
Trace: Looking up host "139.255.47.238"
Trace: Connecting to 139.255.47.238 port 22
Trace: We claim version: SSH-2.0-PuTTY_Local:_Aug_24_2015_15:56:07
Trace: Server version: SSH-2.0-CoreFTP-0.3.2
Trace: Using SSH protocol version 2
Trace: Using Diffie-Hellman with standard group "group14"
Trace: Doing Diffie-Hellman key exchange with hash SHA-1
Trace: Network error: Software caused connection abort
Error: Network error: Software caused connection abort
Trace: CControlSocket::DoClose(64)
Trace: CSftpControlSocket::ResetOperation(66)
Trace: CControlSocket::ResetOperation(66)
Error: Could not connect to server
Trace: CFileZillaEnginePrivate::ResetOperation(66)
Status: Waiting to retry...
Trace: CControlSocket::DoClose(64)
Trace: CControlSocket::DoClose(64)
Error: Connection attempt interrupted by user

[Tim Kosse]

The server is on the fritz. Please contact your server administrator or server hosting provider for assistance so that the server can be fixed.

[bluespy]

I could still connect with it normally with version (3.12.0.2).
Even now, I just downgraded to that version so I could connect to that server.

[Tim Kosse]

Your server chokes on a Key Exchange Init packets containing many algorithms.

Recent versions of FileZilla support more algorithms than previous versions.

If using other clients that support many algorithms, such as OpenSSH, the connection to your server fails as well.

[bluespy]

Client? So, it's the issue with OpenSSH on client side?

Thanks for the explanation.

[Tim Kosse]

As I said multiple times before, it's a server-side issue.