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This is a really weird problem. The first few times I try to connect Filezilla just hangs on the line 211-Extended features supported: for a while before coming up and saying Error: Could not connect to server. The filezilla log below:

Command:    PASS ***********
Response:   230 User logged in.
Command:    FEAT
Response:   211-Extended features supported:
Error:  Could not connect to server

The weird thing is if I keep trying to connect eventually it just works and connects fine. After Filezilla knows which features the server supports it stops asking for a while which enables you to connect first time until Filezilla decides it wants to double check the features list again. I'm at a loss on how to debug this.

Has anyone experienced similar?

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Update: I get a very similar problem when using SmartFTP. [12:20:39] PASS (hidden) [12:20:39] 230 User logged in. [12:20:39] SYST [12:20:39] 215 Windows_NT [12:20:39] Detected Server Type: Windows NT [12:20:39] RTT: 34.292 ms [12:20:39] FEAT [12:20:39] 211-Extended features supported: [12:20:58] Server closed connection [12:20:58] An established connection was aborted by the software in your host machine. [12:20:58] Connect failed. Waiting to retry (30s)... – Max Jul 23 '10 at 11:22
This fixed the issue for me:… – ErJab Jul 21 '11 at 0:30

I had the same problem using FTP for IIS with FileZilla and other clients. The root cause is still a mystery to me. However, if you manage the server, a workaround is to disallow the FEAT command.

For IIS 7.5: IIS Manager -> FTP Request Filtering -> Deny Command

I cannot advise regarding earlier IIS versions.

The server will then respond to FEAT with "500 'FEAT': command not allowed". FileZilla handles this gracefully and goes on to complete the connection.

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Thanks a bunch for this. – ErJab Jul 21 '11 at 0:29

No, I never seen this problem, but it seams a server problem. Do you manage it ? What are logs ?

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Not solved it no. Where would I find the logs? – Max Jul 26 '10 at 15:54

The FEAT command is part of new FTP protocol extension implemented in IIS 7 / 7.5 to allow hosting of multiple FTP with same IP / Port. See:

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Already answered by Brent - almost 1 year ago.. – pauska Oct 7 '11 at 12:31

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