MemoryStream??

  • Thread starter Thread starter Charles A. Lackman
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Charles A. Lackman

Hello,

I am working on an updater that Retrieves a file from a web page.


GetRequest.Method = "POST"

SW = New StreamWriter(TheRequest.GetRequestStream)
SW.WriteLine(TransferName)
SW.Close()
TheResponse = TheRequest.GetResponse()
ms = New MemoryStream()
CopyData(TheResponse.GetResponseStream(), ms)
ms.Seek(0, SeekOrigin.Begin)
System.IO.Directory.CreateDirectory(TransferFolder)
Dim st As FileStream = New FileStream(CompleteName, FileMode.Create)
ms.WriteTo(st)
st.Close()
ms.Close()

The application works good about 90% of the time I have noticed that when
the file is really big like 25 Megs, it stops sending at about 16 Megs. Is
this because the computer does not have enough memory to store the complete
file? or could it be something with the web page that is responding to the
request? or could it be something else.

Any suggestions will be greatly appreciated and even modifications to my
code above. I am not sure how to make the memory stream write to the file
every Meg to test the theory.

Thanks,
Chuck
 
I receive the following Error Message.

unable to read data from transport connection

Thanks,

Chuck
 
Replies only posted in microsoft.public.dotnet.general

Charles A. Lackman wrote:

Please don't cross-post. How did you figure
microsoft.public.dotnet.framework.windowsforms was involved in the problem?

Some good advice for getting good response can be found at
,
http://www.chiark.greenend.org.uk/~sgtatham/bugs.html
I receive the following Error Message.

unable to read data from transport connection
Click to expand...

Please include the entire exception, you can get it by (for example):

catch(Exception e) {
Console.WriteLine("EXCEPTION:\n{0}", e);

This will include a stack-trace which makes it possible to pinpoint
where in your program the error ocurred.

BTW: It seems rather a waste to read the entire received file into
memory. Is there something wrong with just writing it directly to the disk?

What's wrong with simply:

void Copy(Stream instream, Stream outstream, byte[] buf) {
int r;
while ( true ) {
r = instream.Read(buf, 0, buf.Length);
if ( r == 0 )
break;
outstream.Write(buf, 0, r);
}
}

using ( Stream s = new FileStream(CompleteName, FileMode.Create) )
Copy(TheResponse.GetResponseStream(), s);
}
 
For one, if your intent is to store it in a file and never use it in memory
then you simply need to put it into the file stream directly. I would
recommend using a buffered loop to stream the file data from the response
stream to the file stream until there is no more data.

c# but easily translated and maybe this is what copy data is?:
FileStream fos = new FileStream(Name, FileMode.Create);
byte[] buf = new byte[4096];
int bytes = 0;
while((bytes = TheResponse.Read(buf, 0, 4096)) > 0) {
fos.Write(buf, 0, bytes);
}
fos.close();
TheResponse.close();

Do you get any exceptions for the failure? Could it be a timeout that you
are experiencing?

Fred
 
Hello,

I have rewritten the stream directly to a file and still get the same error
(Freeze). I also changed the Session timeout on my server to last longer
(still same problem). Hmmm??

The Error I get is:

unable to read data from transport connection

Code For CopyData:

Private Sub CopyData(ByVal FromStream As Stream, ByVal ToStream As Stream)
Dim intBytesRead As Integer
Dim Counter As Integer = 0
Const intSize As Integer = 1024
Dim bytes(intSize) As Byte
ProgressBar1.Step = 1024
intBytesRead = FromStream.Read(bytes, 0, intSize)
While intBytesRead > 0
ToStream.Write(bytes, 0, intBytesRead)
intBytesRead = FromStream.Read(bytes, 0, intSize)
end Sub

Chuck


Fred Hirschfeld said:
For one, if your intent is to store it in a file and never use it in
memory
then you simply need to put it into the file stream directly. I would
recommend using a buffered loop to stream the file data from the response
stream to the file stream until there is no more data.

c# but easily translated and maybe this is what copy data is?:
FileStream fos = new FileStream(Name, FileMode.Create);
byte[] buf = new byte[4096];
int bytes = 0;
while((bytes = TheResponse.Read(buf, 0, 4096)) > 0) {
fos.Write(buf, 0, bytes);
}
fos.close();
TheResponse.close();

Do you get any exceptions for the failure? Could it be a timeout that you
are experiencing?

Fred

Charles A. Lackman said:
Hello,

I am working on an updater that Retrieves a file from a web page.


GetRequest.Method = "POST"

SW = New StreamWriter(TheRequest.GetRequestStream)
SW.WriteLine(TransferName)
SW.Close()
TheResponse = TheRequest.GetResponse()
ms = New MemoryStream()
CopyData(TheResponse.GetResponseStream(), ms)
ms.Seek(0, SeekOrigin.Begin)
System.IO.Directory.CreateDirectory(TransferFolder)
Dim st As FileStream = New FileStream(CompleteName, FileMode.Create)
ms.WriteTo(st)
st.Close()
ms.Close()

The application works good about 90% of the time I have noticed that when
the file is really big like 25 Megs, it stops sending at about 16 Megs. Is
this because the computer does not have enough memory to store the complete
file? or could it be something with the web page that is responding to
the
request? or could it be something else.

Any suggestions will be greatly appreciated and even modifications to my
code above. I am not sure how to make the memory stream write to the
file
every Meg to test the theory.

Thanks,
Chuck
Click to expand...
Click to expand...
 
NOTE:

I am grabbing 4 files, three of which are under 10 megs. The larger file of
26 megs the third file to download. All the other files download just fine.
It's just the file that is over 15 Megs is size.

Chuck


Fred Hirschfeld said:
For one, if your intent is to store it in a file and never use it in
memory
then you simply need to put it into the file stream directly. I would
recommend using a buffered loop to stream the file data from the response
stream to the file stream until there is no more data.

c# but easily translated and maybe this is what copy data is?:
FileStream fos = new FileStream(Name, FileMode.Create);
byte[] buf = new byte[4096];
int bytes = 0;
while((bytes = TheResponse.Read(buf, 0, 4096)) > 0) {
fos.Write(buf, 0, bytes);
}
fos.close();
TheResponse.close();

Do you get any exceptions for the failure? Could it be a timeout that you
are experiencing?

Fred

Charles A. Lackman said:
Hello,

I am working on an updater that Retrieves a file from a web page.


GetRequest.Method = "POST"

SW = New StreamWriter(TheRequest.GetRequestStream)
SW.WriteLine(TransferName)
SW.Close()
TheResponse = TheRequest.GetResponse()
ms = New MemoryStream()
CopyData(TheResponse.GetResponseStream(), ms)
ms.Seek(0, SeekOrigin.Begin)
System.IO.Directory.CreateDirectory(TransferFolder)
Dim st As FileStream = New FileStream(CompleteName, FileMode.Create)
ms.WriteTo(st)
st.Close()
ms.Close()

The application works good about 90% of the time I have noticed that when
the file is really big like 25 Megs, it stops sending at about 16 Megs. Is
this because the computer does not have enough memory to store the complete
file? or could it be something with the web page that is responding to
the
request? or could it be something else.

Any suggestions will be greatly appreciated and even modifications to my
code above. I am not sure how to make the memory stream write to the
file
every Meg to test the theory.

Thanks,
Chuck
Click to expand...
Click to expand...
 
Fred said:
c# but easily translated and maybe this is what copy data is?:
FileStream fos = new FileStream(Name, FileMode.Create);
byte[] buf = new byte[4096];
int bytes = 0;
while((bytes = TheResponse.Read(buf, 0, 4096)) > 0) {
fos.Write(buf, 0, bytes);
}
fos.close();
TheResponse.close();
Click to expand...

The above code leaks the openend file in case of exceptions, and the use
of 4096 as a constant for Read would probably be better substituted with
buf.Length.

And you would probably want some cleanup code to remove the file if
something goes wrong, something along the lines of:

Stream s = null;
try {
using ( s = new FileStream(Name, FileMode.Create) ) {
byte[] buf = new byte[size];
int r;
while ( (r = TheResponse.Read(buf,0,buf.Length) != 0 )
s.Write(buf, 0, r);
} catch ( Exception e ) {
if ( s != null )
File.Delete(Name);
throw;
}
 
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