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FTP - 503 - Server Unavailable Error

    Question

  • Hi,

     

    I am having a VB.Net 2.0 application which connects to a FTP Server and downloads certain files. The application is working fine in most of the machines. However, the application was installed in one of the machines recently and the application is now returning Server Unavailable (503) Error.

     

    The application is running within the Intranet and the application is working perfectly on all other machines on the network. The problem is occuring only to this particular machine. Also, from the same machine I have tried to connect to the FTP Server in question (using command prompt) and I was able to connect and download the file successfully.

     

    It only seems that the application is facing problem when I try to access it through the .Net application. Does anyone has any idea as to why this error is occuring? If you do please help me out. Urgent

     

    Regards

     

    Vineed

    Tuesday, January 22, 2008 1:09 PM

All replies

  • Just a hint:are there any proxies involved in your environment?

    How does your application connect to the FTP server? What API does it use?

     

    --
    With best regards, Vadym Stetsiak.
    Wednesday, January 23, 2008 9:43 PM
  • Hi Vadym,

     

    Thanks for your time. Yes, there is a proxy involved in the environment. But the other machines, where the application is working fine also work with the same proxy. Is there something I need to change if I connect to the Server using a proxy?

     

    I am using the WebClient class of .Net Framework 2.0. I also tried using the FTPWebRequest, but still the same problem is occuring.

     

    Thanks again..

     

    Regards

     

    Vineed

    Thursday, January 24, 2008 4:23 AM
  • If you have an access to the proxy server try to see it's logs and event log.  Just to make sure that request is processed by it and sent further to the FTP server.

    You can have the same issue as here ( http://www.codeprof.com/dev-archive/198/5-478-1984080.shtm )

     

    If proxy is sending request to the FTP server then there is a problem on the FTP server side

    --

    With best regards, Vadym Stetsiak.
    Blog: http://vadmyst.blogspot.com

     

    Thursday, January 24, 2008 8:03 AM
  • Hi Vadym,

     

    Thanks for your time. I will try your suggestions today itself. Also I will try to set the particular machine in which I am facing the problem to directly access the FTP Server, rather than the proxy server.

     

    I will get back to you with the results as soon as possible

     

    Thanks again...

     

    Regards

     

    Vineed

    Friday, January 25, 2008 4:41 AM
  • Hi Vadym,

     

    Sorry for the late reply (Busy with an application deployment). I removed the proxy and tried to connect to the FTP Server using the Application, but it is still returning the same error. Also, the system administrator informed me that the proxy server does not block or does anything when connecting to a machine within the Intranet. So, the chances of Proxy being the problem does not occur.

     

    I checked the Event Viewer of the FTP Server and it did not provide any error or warning that might stop the file transfer. Is there any other log I need to check on the FTP Server, that might be helpful?

     

    Thanks

     

    Regards

     

    Vineed

     

    Tuesday, January 29, 2008 12:03 PM
  • Well, there is a way in .NET Framework to log what is happening under the hood in FtpWebRequest.

    It is done via network tracing with trace listeners.

     

    Here are the urls that will help you configure tracing.

     

    http://www.groupsrv.com/dotnet/about162406.html

     

    http://msdn2.microsoft.com/en-us/hyb3xww8.aspx

    and

    http://msdn2.microsoft.com/en-us/ty48b824.aspx

     

    HTH

    --
    With best regards, Vadym Stetsiak.
    Blog: http://vadmyst.blogspot.com

    Tuesday, January 29, 2008 1:00 PM
  • Hi Vadym,

     

    Thanks for your time and effort. Really appreciated. I will look into the link and try to generate the log. Also one more bit of information that might be useful is that the OS on which the application is working is Windows 98. Is there some thing that I need to do in case of Win 98 machines. There are other machines with Win 98, but they are working fine. Is there some thing specific I need to look out in Win 98

     

    Thanks again...

     

    Regards

     

    Vineed

    Tuesday, January 29, 2008 1:09 PM