"Bad Sequence of Commands" FTP Error

2006-01-29

Question

_{Sunday, January 29, 2006 8:16 AM | 1 vote}

I'm getting a strange error in my VB FTP program. It works fine when I download a file from an FTP server, but the second time that I download the same file i get "503 Bad Sequence of Commands".

If I download one file, download 3 other files, and then try to download the first file again, I get the error. If I close the program and open it again, the error is gone when I try to download the file.

Is there some command that I need to send the server to unlock the file or something?

All replies (15)

_{Sunday, January 29, 2006 8:32 AM ✅Answered | 5 votes}

I fixed it.

If anyone is interested, I had to set the KeepAlive property of my request to false. Even thought the request object was destroyed, it was still keeping the connection to the file open.

_{Monday, April 24, 2006 12:19 PM}

Hi
I have the same problem as you had. but when i try to fix it with setting KeeAlive property to false i get an error saying " This operation cannot be performed after the request has been submitted." .I have it like this in my code:
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
request.KeepAlive = false;

and MSDN says

"Changing KeepAlive after calling the GetRequestStream, BeginGetRequestStream, GetResponse, or BeginGetResponse method causes an InvalidOperationException exception."

I don't know where i should put this line. I supposed that it should be right after i don't need the request anymore.Am i wrong?

Can you please help me?

Thanks

_{Monday, April 24, 2006 12:22 PM}

Tnx , i fixed it. I put it right after creating WebRequest

_{Friday, December 15, 2006 10:07 AM | 1 vote}

Yes it fixes the problem but it forces you to open and close the ftp connection for every operation, which is not acceptable when you have multiple operations to perform :-(

This problem occurs only with a Unix ftp server, not with a Microsoft one. Thanks, Bill....

_{Monday, November 26, 2007 6:40 PM}

I am using a webclient object to download/upload multiple files to/from a remote ftp server. Sometimes it runs just fine and sometimes it gives me error : 503 bad sequence of commands. There is no "keepalive" property of the webclient which I can set to false according to the solution given above. How can I make sure that it will run fine everytime.

private Exception Upload(WebClient client, string RemoteFile, string LocalFile)

{

Exception retErr = null;

// Get the file name from the local file to name the file on the remote

string Filename = Path.GetFileName(LocalFile);

// Add the file name that the file will be called on the FTP site.

string WebResources = RemoteFile + Filename;

try

{

// Transfer the file to the FTP site.

client.UploadFile(WebResources, LocalFile);

}

catch (Exception ex)

{

// If any errors occurred report it to the caller.

retErr = ex;

}

return retErr;

}

_{Thursday, October 16, 2008 5:58 AM}

Hello, I got the same problem with System.Net.WebClient.UploadFile(String address, String fileName)

Error occurs : The remote server returned an error: (503) Bad sequence of commands.

How do I solve this problem? Many thanks in advance.

_{Tuesday, November 24, 2009 6:39 AM | 1 vote}

Close and Reset the ftp connection after every ftp command when you are connecting to Unix ftp server... :)
This should resolve the problem : "The remote server returned an error: (503) Bad sequence of commands"...
This should work.......... :)

_{Thursday, March 25, 2010 9:18 PM}

TakTeek.. Thanks you saved me on this one. I was good in dev until it went to a system test machine. Apparently some machine keep connections open and some don't by default. I just started bashing ssis that was hosting my code until I read your post. Appreciate it..NET developer

_{Tuesday, April 27, 2010 9:23 PM}

Hi community,

You saved my day, Takteek! Thumbs up!

_{Saturday, August 6, 2011 2:29 PM}

hi,

i have a same problem... i tried sevaral code but no success... can someone provide me the sample code for ftp(UNIX) uploading ...

thanks

sajjad

C U On Net : sajjad_pexsol@yahoo.com

_{Monday, January 16, 2012 10:10 AM}

Thank you very much. I too fixed the issue by setting false to KeepAlive propery of request object.

_{Friday, February 3, 2012 6:09 PM}

@begeek99 +1 you are right , i was getting the same exception then i set KeepAlive to false and turns out it is very slow, i have done some math on this. and setting the KeepAlive flag to false will increase file transfer time by 43% on average. which is not acceptable when you are transferring hundreds of files, so this is not really a solution rather a workaround, still searching for a solution though

_{Sunday, November 11, 2012 7:32 PM}

Abhijit K:

I'm new to vb. Could you help me do that? lol. Here's my code:

 Dim create As System.IO.FileStream
        Dim server = "ftp://ftp.freehostia.com/UploadLocationDirectory/"

        create = System.IO.File.Create("C:/file.txt")
        create.Close()

        My.Computer.FileSystem.WriteAllText("C:/file.txt", TextBox1.Text, False)

        My.Computer.Network.UploadFile("C:/file.txt", server & "uploadedfile.html", "Username", "Password")

        My.Computer.FileSystem.DeleteFile("C:/file.txt")

The code starts out by creating a new text file, then writing data to the new file, then uploading it to FTP, then deleting it off the computer.

_{Wednesday, September 16, 2015 8:50 AM}

I have used WebClient.DownloadFile() before FtpWebRequest.Method = WebRequestMethods.Ftp.ListDirectory, then made WebResponse.GetResponse() throw the exception ever.

Has no solution except replace WebClient.DownloadFile() by FtpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile.

_{Wednesday, September 16, 2015 8:53 AM}

Hello, I got the same problem with System.Net.WebClient.UploadFile(String address, String fileName)

Error occurs : The remote server returned an error: (503) Bad sequence of commands.

How do I solve this problem? Many thanks in advance.

I have used WebClient.DownloadFile() before FtpWebRequest.Method = WebRequestMethods.Ftp.ListDirectory, then made WebResponse.GetResponse() throw the exception ever.

Has no solution except replace WebClient.DownloadFile() by FtpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile.

I think you can replace WebClient.UploadFile() by FtpWebRequest.Method = WebRequestMethods.Ftp.UploadFile.

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"Bad Sequence of Commands" FTP Error

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