In my application I am uploading a file by using Orielly utility. If a particular file is already uploaded then I redirect the user to an error page with a proper mesg, using sendRedirect(). When I am not using a proxy while testing the application it works perfectly. When I am using a proxy and try to upload the duplicate file i get a TCP_ERROR : - The system was unable to communicate with the server. I think this is happening while redirecting. Thanks for any clues in advance. -Kaustubh.