Question

SFTP connexion not working anymore

Posted January 21, 2015 2.1k views

Hello I have a problem. I followed this tutorial :
https://www.digitalocean.com/community/tutorials/how-to-use-filezilla-to-transfer-and-manage-files-securely-on-your-vps

It was working for months but since a week it’s not working anymore. I haven’t change anything and I’m not able to understand what’s happening through Filezilla’s log. Here it is.

Response:   fzSftp started
Trace:  CSftpControlSocket::ConnectParseResponse(fzSftp started)
Trace:  CSftpControlSocket::SendNextCommand()
Trace:  CSftpControlSocket::ConnectSend()
Command:    keyfile "C:\Users\Aurélien\my_keys\gg_private.ppk"
Trace:  CSftpControlSocket::ConnectParseResponse()
Trace:  CSftpControlSocket::SendNextCommand()
Trace:  CSftpControlSocket::ConnectSend()
Command:    open "xxx@xxx.xxx.xxx.xxx" 22
Trace:  Looking up host "xxx.xxx.xxx.xxx"
Trace:  Connecting to xxx.xxx.xxx.xxx port 22
Trace:  We claim version: SSH-2.0-PuTTY_Local:_Jan__7_2015_14:17:27
Trace:  Server version: SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
Trace:  We believe remote version has SSH-2 channel request bug
Trace:  Using SSH protocol version 2
Trace:  Doing ECDH key exchange with hash SHA-256
Trace:  Host key fingerprint is:
Trace:  ecdsa-sha2-nistp256 d5:e8:ca:a6:69:ae:dd:68:21:07:1d:17:c7:48:86:9b
Command:    Trust new Hostkey: Once
Trace:  Initialised AES-256 SDCTR client->server encryption
Trace:  Initialised HMAC-SHA-256 client->server MAC algorithm
Trace:  Initialised AES-256 SDCTR server->client encryption
Trace:  Initialised HMAC-SHA-256 server->client MAC algorithm
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...

It seems to be a server problem as stated here
Trace: We believe remote version has SSH-2 channel request bug

Thanks for the help you could bring me.

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1 answer

Can be. But you can’t completely blame the server. There are multiple solutions for this

  1. Update your putty
  2. Modify ‘Algorithm Selection policy’ (In putty, Connection > SSH > Kex) in putty. Some policy may not work with the server. You need to change the order in it. 'Diffie-Helman group 14’ or 'Diffie-Helman group exchange’ on the top will normally work.

Most of the cases these worked for me.

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