Therefore, a firewall between the client and the server is blocking the connection that the client is trying to initiate to the server. But as soon as you try to do a directory listing over the data connection it fails. In your scenario, it appears you have successfully created the control connection and logged in. The data connection occurs over a random port designated by the server. In modern IT networks, this doesn’t work very well because most clients sit behind a NAT’d network and it would require port forwarding.Īs a work around, passive mode causes the client to initiate both the control connection and the data connection. In FTP active mode, your client initiates the control connection to the server, and the server initiates the data connection to the client. The actual data, like a file listing or directory listing is sent over the data connection. FTP commands are sent and responses are received over the control connection. To give a little background, when you connect to an FTP server there is a control connection, and a data connection established. Most server/client FTP scenarios work in passive mode and you can see in the log that your client has switched to PASV mode. This is usually a problem with the active/passive mode of FTP. Trace: CFileZillaEnginePrivate::ResetOperation(2) Trace: CFtpListOpData::SubcommandResult() in state 3Įrror: Failed to retrieve directory listing Trace: CControlSocket::ParseSubcommandResult(2) Trace: CFtpControlSocket::ResetOperation(2) Trace: CFtpRawTransferOpData::ParseResponse() in state 4 Response: 425 Can't open data connection for transfer of "/" Trace: Binding data connection source IP to control connection source IP 10.0.0.4 Trace: CFtpRawTransferOpData::Send() in state 4 Trace: CFtpRawTransferOpData::ParseResponse() in state 2 Response: 227 Entering Passive Mode (*SERVER IP*,234,225) Trace: CFtpRawTransferOpData::Send() in state 2 Trace: CFtpRawTransferOpData::ParseResponse() in state 1 Trace: CFtpRawTransferOpData::Send() in state 1 Status: Connecting to **SERVER IP**:2121. Status: Directory listing of "/" successful Trace: CFtpListOpData::ListSend() in state 2 Trace: CFtpListOpData::SubcommandResult() in state 1 Trace: CControlSocket::ParseSubcommandResult(0) Trace: CFtpChangeDirOpData::ParseResponse() in state 1 Trace: CFtpChangeDirOpData::Send() in state 1 Trace: CFtpChangeDirOpData::Send() in state 0 Trace: CFtpListOpData::ListSend() in state 0 Trace: CFtpControlSocket::ResetOperation(0) Trace: CFtpLogonOpData::ParseResponse() in state 5 Response: 331 Password required for printiq Trace: CFtpLogonOpData::Send() in state 5 Status: Insecure server, it does not support FTP over TLS. Trace: CFtpLogonOpData::ParseResponse() in state 3 Trace: CFtpLogonOpData::Send() in state 3 Trace: CFtpLogonOpData::ParseResponse() in state 2 Response: 502 Explicit TLS authentication not allowed Trace: CFtpLogonOpData::Send() in state 2 Trace: CFtpLogonOpData::ParseResponse() in state 1 Status: Connection established, waiting for welcome message. Status: Resolving address of *SERVER DNS* Trace: CFtpLogonOpData::Send() in state 0 Trace: CFileZillaEnginePrivate::ResetOperation(0) Trace: CFileZillaEnginePrivate::ResetOperation(66) Trace: CControlSocket::ResetOperation(66) Trace: CFtpControlSocket::ResetOperation(66) Successful Status: Disconnected from server Why does the connection succeed on 1 server but fail on another?īoth of our servers connecting to customers FTP are in Azure, both are VM's running the same OS I've set the debug option in FileZilla Client and below are both the successful and failed connections. The connection works from my office, and from all of our Azure servers except one. Our customer has a FileZilla FTP Server running on a Windows box and I'm using FileZilla Client to test the connection.
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