我在这里是因为在通过ftp协议(protocol)下载某些文件时遇到问题。这很奇怪，因为它偶尔发生，甚至对于同一单个文件也是如此。
只是一个精度:我正在下载非常大的文件(从500 Mo到30Go)
这是我的函数返回的异常类型:(抱歉，它是法语的)System.Net.WebException: La connexion sous-jacente a été fermée : Une erreur inattendue s'est produite lors de la réception. à System.Net.FtpWebRequest.CheckError() à System.Net.FtpWebRequest.SyncRequestCallback(Object obj) à System.IO.Stream.Close() à System.Net.ConnectionPool.Destroy(PooledStream pooledStream) à System.Net.ConnectionPool.PutConnection(PooledStream pooledStream, Object owningObject, Int32 creationTimeout, Boolean canReuse) à System.Net.FtpWebRequest.FinishRequestStage(RequestStage stage) à System.Net.FtpWebRequest.SyncRequestCallback(Object obj) à System.Net.CommandStream.Abort(Exception e) à System.Net.CommandStream.CheckContinuePipeline() à System.Net.FtpDataStream.System.Net.ICloseEx.CloseEx(CloseExState closeState) à System.Net.FtpDataStream.Dispose(Boolean disposing) à System.IO.Stream.Close() à UtilityClasses.FTP.Download(String srcDirectoryPath, String file, String destDirectoryPath)
这是用于下载的代码:
下载方法:
public Dictionary<string, object> Download(string srcDirectoryPath, string file, string destDirectoryPath, int attemptLimitNb, int delay)
{
int attemptNb = 0;
bool downloadFailed;
Dictionary<string, object> result = new Dictionary<string,object>();
do
{
attemptNb++;
result = Download(srcDirectoryPath, file, destDirectoryPath);
downloadFailed = result["downloadfailed"] != null;
if (downloadFailed) Thread.Sleep((int)(1000 * delay));
}
while (downloadFailed && attemptNb < attemptLimitNb);
return result;
}
public Dictionary<string, object> Download(string srcDirectoryPath, string file, string destDirectoryPath)
{
Exception downloadFailed = null;
Dictionary<string, object> result = new Dictionary<string, object>();
bool fileFound = false;
try
{
if (destDirectoryPath == null || !Directory.Exists(destDirectoryPath)) throw new Exception("Download destination path does not exist");
if (file != null && file != "")
{
if (file.Contains("/"))
{
throw new Exception("Invalid file name. Impossible to download");
}
Uri serverUri;
if (srcDirectoryPath == null || srcDirectoryPath == "")
{
serverUri = new Uri("ftp://" + this.Server + "/" + file);
}
else if (Regex.IsMatch(srcDirectoryPath, "^/.*$") || Regex.IsMatch(srcDirectoryPath, "^.*/$"))
{
throw new Exception("Path must not start and end with '/'");
}
else
{
serverUri = new Uri("ftp://" + this.Server + "/" + srcDirectoryPath + "/" + file);
}
if (serverUri.Scheme != Uri.UriSchemeFtp) throw new Exception("server URI Scheme does not match FTP URI Scheme");
if (Exists(srcDirectoryPath, file))
{
fileFound = true;
FtpWebRequest downloadRequest = (FtpWebRequest)FtpWebRequest.Create(serverUri);
downloadRequest.Credentials = new NetworkCredential(UserName, Password);
downloadRequest.KeepAlive = false;
downloadRequest.Method = WebRequestMethods.Ftp.DownloadFile;
FtpWebResponse response = (FtpWebResponse)downloadRequest.GetResponse();
Stream responseStream = response.GetResponseStream();
FileStream fileStream = new FileStream(Path.Combine(destDirectoryPath, file), FileMode.Create);
byte[] buffer = new byte[2000];
int read = 0;
try
{
do
{
read = responseStream.Read(buffer, 0, buffer.Length);
fileStream.Write(buffer, 0, read);
fileStream.Flush();
}
while (read != 0);
}
catch (Exception e)
{
fileStream.Close();
responseStream.Close();
response.Close();
throw e;
}
fileStream.Close();
responseStream.Close();
response.Close();
}
}
}
catch (WebException webExcptn)
{
downloadFailed = webExcptn;
}
finally
{
result.Add("filefound", fileFound);
result.Add("downloadfailed", downloadFailed);
}
return result;
}
存在方法:
public bool Exists(string srcPath, string elementName)
{
if (elementName == null || elementName == "")
{
return false;
}
Uri serverUri;
bool res = false;
if (srcPath == null || srcPath == "")
{
serverUri = new Uri("ftp://" + this.Server);
}
else if (Regex.IsMatch(srcPath, "^/.*$") || Regex.IsMatch(srcPath, "^.*/$"))
{
throw new Exception("Path must not start and end with '/'");
}
else
{
serverUri = new Uri("ftp://" + this.Server + "/" + srcPath);
}
if (serverUri.Scheme != Uri.UriSchemeFtp) throw new Exception("server URI Scheme does not match FTP URI Scheme");
FtpWebRequest listingRequest = (FtpWebRequest)FtpWebRequest.Create(serverUri);
listingRequest.Credentials = new NetworkCredential(UserName, Password);
listingRequest.KeepAlive = false;
listingRequest.Method = WebRequestMethods.Ftp.ListDirectory;
FtpWebResponse response = (FtpWebResponse)listingRequest.GetResponse();
Stream responseStream = response.GetResponseStream();
StreamReader streamReader = new StreamReader(responseStream);
string ftpElementName;
do
{
ftpElementName = Path.GetFileName(streamReader.ReadLine());
if (ftpElementName == null) break;
else
{
string pattern = "^" + elementName.Replace("[", "\\[").Replace("]", "\\]").Replace("+", "[+]").Replace(".", "[.]") + "$";
if (Regex.IsMatch(ftpElementName, pattern, RegexOptions.IgnoreCase))
{
res = true;
}
}
}
while (ftpElementName != null && !res);
streamReader.Close();
responseStream.Close();
response.Close();
return res;
}
也许这是超时问题，但我真的不知道。我花了很长时间寻找答案，但没有成功。也许你们中的一些人会找到解决方案。
///
编辑:一些进展:
我已经在VS的 Debug模式下测试了我的代码，实际上，上面的Exception是上一个代码的结果。 (我不知道，因为我只写了日志文件中返回的最后一个异常)
这是原始的异常(exception):
Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
第二个异常是由Download方法代码的这一部分引起的:
catch (Exception e)
{
fileStream.Close();
responseStream.Close(); // <<<<<<<<<<<<<<
response.Close();
throw e;
}
我继续进行调查，但似乎“超时pb”假说是最一致的。今晚我将尝试使用较大的超时值。
最佳答案
只是想加强ScottE的诊断，并且要更加具体。超时很可能是问题所在。
FtpWebRequest的.Net实现是错误的，或者the MSDN document有错字，FtpWebRequest.Timeout的默认值不是-1(无限)。是100000(100秒)。
此外，还有另一个超时问题。一些测试表明，responseStream的超时值始终为300000(300秒)。我不知道该值是如何分配的。无论如何，需要修改此值以容纳大文件。
总之，解决方案是将FtpWebRequest.Timeout和Stream.Timeout设置为足够大的值。
关于c# - 基础连接已关闭:接收时发生意外错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/6304689/