The FTP client has not yet connected to the server

Question

I've seen a few posts from years ago, but I haven't seen anything recent. What am I missing? Connecting to a simple sFTP server with user/password auth, and I can list files in a directory. But when I try to check if a file exists, I receive the error that "The FTP client has not yet connected to the server.  The requested action cannot be performed until after a connection has been established."

This did not happen in the previous version I was using, 10.1. It only happened once I moved to the latest version, 12.5.0.

sftp.Connect();
var remoteFiles = sftp.ListDirectory(dataDirectory);
foreach (FTPFile remoteFile in remoteFiles)
{
    if (remoteFile.Dir)
        continue;
    // check if this file is already in another directory
    string anotherName = OtherDirectoryName + remoteFile.Name;
    if (sftp.Exists(anotherName ))   <<<<<< problem here

EnterpriseDT.Net.Ftp.FTPException
  HResult=0x80131600
  Message=The FTP client has not yet connected to the server.  The requested action cannot be performed until after a connection has been established.
  Source=edtFTPnetPRO
  StackTrace:
   at EnterpriseDT.Net.Ftp.FTPClient.pE4vf83jcr(Boolean  )
   at EnterpriseDT.Net.Ftp.FTPClient.Exists(String remoteFile)
   at EnterpriseDT.Net.Ftp.FTPConnection.Exists(String remoteFile)

The FTP component is setup with a username and password.

Protocol = FileTransferProtocol.SFTP,

ServerValidation = SecureFTPServerValidationType.None,
 

Log (I hope the relevant sections - I'm limited in what I can post)

DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.159 :  User authentication successful
......
DEBUG [SSHFTPClient] 18 Aug 2025 01:25:13.437 :  Set transfer type = BINARY
DEBUG [FTPConnection] 18 Aug 2025 01:25:13.437 :  Home directory is '/home/user'
DEBUG [FTPConnection] 18 Aug 2025 01:25:13.437 :  GetFileInfos('/home/user/data_qa/')
DEBUG [SSHFTPClient] 18 Aug 2025 01:25:13.437 :  ResolveRemotePath('/home/user/data_qa/'); [cwd='/home/user']
DEBUG [SSHFTPClient] 18 Aug 2025 01:25:13.437 :  Resolved to '/home/user/data_qa'
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.437 :  Send : Name=SSH_FXP_REALPATH,Type=16,RequestID=2
DEBUG [SSH2Channel] 18 Aug 2025 01:25:13.437 :  Transmit 46 bytes
DEBUG [ChannelDataWindow] 18 Aug 2025 01:25:13.437 :  Remote window size decreased to 2097083
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.437 :  Sent 84 bytes (NoDelay=True, SendBufferSize=65536, ReceiveBufferSize=65536)
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.437 :  Packet written to socket
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.484 : FTPConnection.12 RepeatCallback received 132 bytes
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.484 : FTPConnection.12 ProcessPacket pt=SSH_MSG_CHANNEL_DATA
DEBUG [SFTPMessageFactory] 18 Aug 2025 01:25:13.484 : FTPConnection.12 CreateMessage (bufferlength=100,offset=13,length=87,type=104)
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.484 : FTPConnection.12 SSH_FXP_NAME: requestID=2, 1 files
DEBUG [SFTPMessageStore] 18 Aug 2025 01:25:13.484 : FTPConnection.12 AddMessage(2) - added to store
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.484 :  Reply : Name=SSH_FXP_NAME,Type=104,RequestID=2
DEBUG [SFTPSubsystem] 18 Aug 2025 01:25:13.484 :  Opening directory /home/user/data_qa
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.484 :  Send : Name=SSH_FXP_OPENDIR,Type=11,RequestID=3
DEBUG [SSH2Channel] 18 Aug 2025 01:25:13.484 :  Transmit 46 bytes
DEBUG [ChannelDataWindow] 18 Aug 2025 01:25:13.484 :  Remote window size decreased to 2097037
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.484 :  Sent 84 bytes (NoDelay=True, SendBufferSize=65536, ReceiveBufferSize=65536)
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.484 :  Packet written to socket
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.531 : FTPConnection.12 RepeatCallback received 60 bytes
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.532 : FTPConnection.12 ProcessPacket pt=SSH_MSG_CHANNEL_DATA
DEBUG [SFTPMessageFactory] 18 Aug 2025 01:25:13.532 : FTPConnection.12 CreateMessage (bufferlength=26,offset=13,length=13,type=102)
DEBUG [SFTPMessageStore] 18 Aug 2025 01:25:13.532 : FTPConnection.12 AddMessage(3) - added to store
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.532 :  Reply : Name=SSH_FXP_HANDLE,Type=102,RequestID=3
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.532 :  Send : Name=SSH_FXP_READDIR,Type=12,RequestID=4
DEBUG [SSH2Channel] 18 Aug 2025 01:25:13.532 :  Transmit 17 bytes
DEBUG [ChannelDataWindow] 18 Aug 2025 01:25:13.532 :  Remote window size decreased to 2097020
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.533 :  Sent 60 bytes (NoDelay=True, SendBufferSize=65536, ReceiveBufferSize=65536)
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.533 :  Packet written to socket
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.582 : FTPConnection.12 RepeatCallback received 7676 bytes
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.582 : FTPConnection.12 ProcessPacket pt=SSH_MSG_CHANNEL_DATA
DEBUG [SFTPMessageFactory] 18 Aug 2025 01:25:13.582 : FTPConnection.12 CreateMessage (bufferlength=7646,offset=13,length=7633,type=104)
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.582 : FTPConnection.12 SSH_FXP_NAME: requestID=4, 39 files
DEBUG [SFTPMessageStore] 18 Aug 2025 01:25:13.582 : FTPConnection.12 AddMessage(4) - added to store
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.582 :  Reply : Name=SSH_FXP_NAME,Type=104,RequestID=4
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.582 :  Send : Name=SSH_FXP_READDIR,Type=12,RequestID=5
DEBUG [SSH2Channel] 18 Aug 2025 01:25:13.582 :  Transmit 17 bytes
DEBUG [ChannelDataWindow] 18 Aug 2025 01:25:13.582 :  Remote window size decreased to 2097003
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.582 :  Sent 60 bytes (NoDelay=True, SendBufferSize=65536, ReceiveBufferSize=65536)
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.583 :  Packet written to socket
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.623 : FTPConnection.12 RepeatCallback received 76 bytes
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.623 : FTPConnection.12 ProcessPacket pt=SSH_MSG_CHANNEL_DATA
DEBUG [SFTPMessageFactory] 18 Aug 2025 01:25:13.623 : FTPConnection.12 CreateMessage (bufferlength=41,offset=13,length=28,type=101)
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.623 : FTPConnection.12 ErrorCode|Status=1
DEBUG [SFTPMessageStore] 18 Aug 2025 01:25:13.623 : FTPConnection.12 AddMessage(5) - added to store
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.623 :  Reply : Name=SSH_FXP_STATUS,Type=101,RequestID=5
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.623 :  Send : Name=SSH_FXP_CLOSE,Type=4,RequestID=6
DEBUG [SSH2Channel] 18 Aug 2025 01:25:13.623 :  Transmit 17 bytes
DEBUG [ChannelDataWindow] 18 Aug 2025 01:25:13.623 :  Remote window size decreased to 2096986
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.623 :  Sent 60 bytes (NoDelay=True, SendBufferSize=65536, ReceiveBufferSize=65536)
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.623 :  Packet written to socket
DEBUG [PlainSocket] 18 Aug 2025 01:25:13.667 : FTPConnection.12 RepeatCallback received 68 bytes
DEBUG [SSH2Connection] 18 Aug 2025 01:25:13.667 : FTPConnection.12 ProcessPacket pt=SSH_MSG_CHANNEL_DATA
DEBUG [SFTPMessageFactory] 18 Aug 2025 01:25:13.667 : FTPConnection.12 CreateMessage (bufferlength=37,offset=13,length=24,type=101)
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.667 : FTPConnection.12 ErrorCode|Status=0
DEBUG [SFTPMessageStore] 18 Aug 2025 01:25:13.667 : FTPConnection.12 AddMessage(6) - added to store
DEBUG [SFTPMessage] 18 Aug 2025 01:25:13.667 :  Reply : Name=SSH_FXP_STATUS,Type=101,RequestID=6
DEBUG [FTPConnection] 18 Aug 2025 01:25:15.785 :  Exists(/home/user/data_qa/processed/checkfile.zip)
 

Comments

It looks to me like the server has disconnected the client - is it possible to obtain the server log?

---

I ran another test this morning, to isolate the chatter. It's extremely basic, and looks like it doesn't even receive anything related to the Exists() call.

Aug 18 13:18:29 ip-server-ip sftp-server[12342]: session opened for local user user from [remote.ip]
Aug 18 13:18:29 ip-server-ip sftp-server[12342]: received client version 3
Aug 18 13:18:29 ip-server-ip sftp-server[12342]: realpath "."
Aug 18 13:18:29 ip-server-ip sftp-server[12342]: realpath "/home/user/data_qa"
Aug 18 13:18:29 ip-server-ip sftp-server[12342]: opendir "/home/user/data_qa"
Aug 18 13:18:30 ip-server-ip sftp-server[12342]: closedir "/home/user/data_qa"
Aug 18 13:21:32 ip-server-ip sftp-server[16734]: session closed for local user user from [remote.ip]

---

Hmm, it just says "session closed" but doesn't explain why that happened. There's no call to the exists method because it checks if the connection is open before calling it.

---

That "session closed" was 3 minutes later, well after I would have encountered the error. I hit the error a couple of seconds - I was debugging - after I received the directory listing. So the connection still would have been active.

This works:
    sftp.Connect();
    var remoteFiles = sftp.ListDirectory(dataDirectory);

This does not work:
    sftp.Connect();
    var exists = sftp.Exists("gabba_gabba_hey");

I hit the exact same error. This really makes me think it's something the Exists() call is doing and not the server.

I do have to correct one thing I said in my original post. I reverted to version 10.1, and the error still occurs. This is a different area of my code than I was thinking of when I wrote the original post.

---

This is getting beyond a public forum post. Please open a ticket and include your log file and as much information as possible.

https://enterprisedt.atlassian.net/servicedesk/customer/portal/1