Hi Dean,
I have done some test on my side and I think the server is really
responsible to release the connection, there's really not much we can do
from the client side.
Here's my test configuration/steps:
1) I downloaded a ftp server Serv-U from
http://www.serv-u.com and
installed on system B, to ease test, I enabled anonymous user to read/write
files on the ftp server
2) On my system A, I created following test program:
============
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Net;
using System.Threading;
namespace ConsoleApplication3
{
class Program
{
static void Main(string[] args)
{
UploadFile(@"f:\test.exe", "ftp://serverB/test.exe", 5000);
Console.WriteLine("Press ENTER");
Console.ReadLine();
}
static bool IsFtpFileExists(string remoteUri, out long remFileSize)
{
FtpWebRequest request =
(FtpWebRequest)WebRequest.Create(remoteUri);
FtpWebResponse response;
request.Method = WebRequestMethods.Ftp.GetFileSize;
try
{
response = (FtpWebResponse)request.GetResponse();
remFileSize = response.ContentLength;
return true;
}
catch (WebException we)
{
response = we.Response as FtpWebResponse;
if (response != null && response.StatusCode ==
FtpStatusCode.ActionNotTakenFileUnavailable)
{
remFileSize = 0;
return false;
}
throw;
}
}
static void UploadFile(string localFile, string remoteUri, int
attempts)
{
FileInfo fi = new FileInfo(localFile);
long remFileSize = 0;
FtpWebRequest request = null;
while (--attempts >= 0)
{
try
{
request = (FtpWebRequest)WebRequest.Create(new
Uri(remoteUri));
request.Timeout = 3000;
if (IsFtpFileExists(remoteUri, out remFileSize))
{
Console.WriteLine("File already exists, RESUME");
request.Method = WebRequestMethods.Ftp.AppendFile;
}
else
{
Console.WriteLine("File not already exists,
UPLOAD");
request.Method = WebRequestMethods.Ftp.UploadFile;
}
request.ContentLength = fi.Length - remFileSize;
request.UsePassive = false;
using (Stream requestStream =
request.GetRequestStream())
{
using (FileStream fs = File.Open(localFile,
FileMode.Open))
{
fs.Seek(remFileSize, SeekOrigin.Begin);
const int BUFFER_SIZE = 8192;
byte[] buffer = new byte[BUFFER_SIZE];
int readBytes = 0;
do
{
readBytes = fs.Read(buffer, 0, BUFFER_SIZE);
requestStream.Write(buffer, 0, readBytes);
System.Threading.Thread.Sleep(500);
} while (readBytes != 0);
}
}
Console.WriteLine("Done");
using (FtpWebResponse response =
(FtpWebResponse)request.GetResponse())
{
Console.WriteLine(response.StatusCode);
}
break;
}
catch (WebException we)
{
Console.WriteLine(we.Message);
Thread.Sleep(500);
}
}
}
}
}
============
3) Run this test program, it will start upload file f:\test.exe to the ftp
server; while it's transfering, disable the network connection "Local Area
Connection" to simulate a connection broken error; and re-enable it again
after some time. From the ftp server, serv-u administrator shows there's a
connection keeps open.
4) Terminate the test program, the connection still opens on the server.
5) Now use another ftp client to test this behavior, you will find the
connection is also kept open on the ftp server. Also, in this case, serv-U
actually don't use temporary file, therefore you can see the target file
exists but while the orphan connection keeps open, you cannot delete or
overwrite file -- it's locked by the thread receiving the file on the ftp
server.
Since using a commercial ftp client also shows behavior, I think we really
cannot do much from client-side. It's totally controlled by the ftp server,
the server decides when to times out and dropps the orphan connection.
Regards,
Walter Wang (
[email protected], remove 'online.')
Microsoft Online Community Support
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