I have solved my problem by introducing a request timeout- which, if reached, makes the program to throw a WebException. In that case, the program resumes the download from the place it left of. Here's my code :
This is inside of a method which is returning true if the file is downloaded, false- otherwise
Digitalez.DirectoryUtil.EnsureDirectoryExists(relativePath);
string filePath = System.IO.Path.Combine(relativePath, fileInfo.Name);
long length = Digitalez.FtpUtil.GetFileLength(fileInfo.FullPath, userName, password, usePassive);
long offset = 0;
int retryCount = 10;
int? readTimeout = 5 * 60 * 1000; //five minutes
// if the file exists, do not download it
if (System.IO.File.Exists(filePath))
{
return false;
}
while (retryCount > 0)
{
using (System.IO.Stream responseStream = Captator.Eifos.Net.FtpUtil.GetFileAsStream(fileInfo.FullPath, userName, password, usePassive, offset, requestTimeout: readTimeout != null ? readTimeout.Value : System.Threading.Timeout.Infinite))
{
using (System.IO.FileStream fileStream = new System.IO.FileStream(filePath, System.IO.FileMode.Append))
{
byte[] buffer = new byte[4096];
try
{
int bytesRead = responseStream.Read(buffer, 0, buffer.Length);
while (bytesRead > 0)
{
fileStream.Write(buffer, 0, bytesRead);
bytesRead = responseStream.Read(buffer, 0, buffer.Length);
}
return true;
}
catch (System.Net.WebException)
{
// Do nothing - consume this exception to force a new read of the rest of the file
}
}
if (System.IO.File.Exists(filePath))
{
offset = new System.IO.FileInfo(filePath).Length;
}
else
{
offset = 0;
}
retryCount--;
if (offset == length)
{
return true;
}
}
}
Digitalez.FtpUtil:
public static System.IO.Stream GetFileAsStream(string ftpUrl, string username, string password, bool usePassive, long offset, int requestTimeout)
{
System.Net.FtpWebRequest request = (System.Net.FtpWebRequest)System.Net.WebRequest.Create(ftpUrl);
request.KeepAlive = false;
request.ReadWriteTimeout = requestTimeout;
request.Timeout = requestTimeout;
request.ContentOffset = offset;
request.UsePassive = usePassive;
request.UseBinary = true;
request.Credentials = new System.Net.NetworkCredential(username, password);
request.Method = System.Net.WebRequestMethods.Ftp.DownloadFile;
System.IO.Stream fileResponseStream;
System.Net.FtpWebResponse fileResponse = (System.Net.FtpWebResponse)request.GetResponse();
fileResponseStream = fileResponse.GetResponseStream();
return fileResponseStream;
}
public static long GetFileLength(string ftpUrl, string username, string password, bool usePassive)
{
System.Net.FtpWebRequest request = (System.Net.FtpWebRequest)System.Net.WebRequest.Create(ftpUrl);
request.KeepAlive = false;
request.UsePassive = usePassive;
request.Credentials = new System.Net.NetworkCredential(username, password);
request.Method = System.Net.WebRequestMethods.Ftp.GetFileSize;
System.Net.FtpWebResponse lengthResponse = (System.Net.FtpWebResponse)request.GetResponse();
long length = lengthResponse.ContentLength;
lengthResponse.Close();
return length;
}
I haven't tried other servers but this certainly does the trick.
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