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Download the first 1000 bytes
I need to download a text file from the internet using C#. The file size can be quiet large and the information I need is always within the first 1000 bytes.
This is what I have so far. I found out that the server might ignore the range header. Is there a way to limit streamreader to only read the first 1000 characters?
string GetWebPageContent(string url)
{
string result = string.Empty;
HttpWebRequest request;
const int bytesToGet = 1000;
request = WebRequest.Create(url) as HttpWebRequest;
//get first 1000 bytes
request.AddRange(0, bytesToGet - 1);
// the following code is alternative, you may implement the function after your needs
using (WebResponse response = request.GetResponse())
{
using (StreamReader sr = new StreamReader(response.GetResponseStream()))
{
result = sr.ReadToEnd();
}
}
return result;
}
Please follow-up in your question from yesterday!
There is a read method that you can specify the number of characters to read.
You can retrieve the first 1000 bytes from the stream, then decode the string from the bytes:
using (WebResponse response = request.GetResponse())
{
using (Stream stream = response.GetResponseStream())
{
byte[] bytes = new byte[bytesToGet];
int count = stream.Read(bytes, 0, bytesToGet);
Encoding encoding = Encoding.GetEncoding(response.Encoding);
result = encoding.GetString(bytes, 0, count);
}
}
Instead of using request.AddRange() which may be ignored by some servers as you said, read 1000 bytes (1 KB = 1024 bytes) from stream and then close it. This is like you get disconnected from server after receiving 1000 bytes. Code:
int count = 0;
int result = 0;
byte[] buffer = new byte[1000];
// create stream from URL as you did above
do
{
// we want to read 1000 bytes but stream may read less. result = bytes read
result = stream.Read(buffer, 0, 1000); // Use try around this for error handling
count += result;
} while ((count < 1000) && (result != 0));
stream.Dispose();
// now buffer has the first 1000 bytes of your request
Related
I have to upload a large file to the server with the following code snippet:
static async Task LordNoBugAsync(string token, string filePath, string uri)
{
HttpWebRequest fileWebRequest = (HttpWebRequest)WebRequest.Create(uri);
fileWebRequest.Method = "PATCH";
fileWebRequest.AllowWriteStreamBuffering = false; //this line tells to upload by chunks
fileWebRequest.ContentType = "application/x-www-form-urlencoded";
fileWebRequest.Headers["Authorization"] = "PHOENIX-TOKEN " + token;
fileWebRequest.KeepAlive = false;
fileWebRequest.Timeout = System.Threading.Timeout.Infinite;
fileWebRequest.Proxy = null;
using (FileStream fileStream = File.OpenRead(filePath) )
{
fileWebRequest.ContentLength = fileStream.Length; //have to provide length in order to upload by chunks
int bufferSize = 512000;
byte[] buffer = new byte[bufferSize];
int lastBytesRead = 0;
int byteCount = 0;
Stream requestStream = fileWebRequest.GetRequestStream();
requestStream.WriteTimeout = System.Threading.Timeout.Infinite;
while ((lastBytesRead = fileStream.Read(buffer, 0, bufferSize)) != 0)
{
if (lastBytesRead > 0)
{
await requestStream.WriteAsync(buffer, 0, lastBytesRead);
//for some reasons didnt really write to stream, but in fact buffer has content, >60MB
byteCount += bufferSize;
}
}
requestStream.Flush();
try
{
requestStream.Close();
requestStream.Dispose();
}
catch
{
Console.Write("Error");
}
try
{
fileStream.Close();
fileStream.Dispose();
}
catch
{
Console.Write("Error");
}
}
...getting response parts...
}
In the code, I made a HttpWebRequest and push the content to server with buffering. The code works perfectly for any files under 60MB.
I tried a 70MB pdf. The buffer array has different content for each buffering. Yet, the request stream does not seem to be getting written. The bytecount also reached 70M, showing the file is properly read.
Edit (more info): I set the break point at requestStream.Close(). It clearly takes ~2 mins for the request stream to write in 60MB files but only takes 2ms for 70MB files.
My calling:
Task magic = LordNoBugAsync(token, nameofFile, path);
magic.Wait();
I am sure my calling is correct (it works for 0B to 60MB files).
Any advice or suggestion is much appreciated.
I am writing an app in C# to measure and display download speed. I have the following code to download a 62MB file in chunks, which seems to work well for my purposes. I plan to extend this to measure the time required for each chunk, so it can be graphed.
Before doing so, I have a few questions to make sure this is actually doing what I think it is doing. Here is the code:
private void DownloadFile()
{
string uri = ConfigurationManager.AppSettings["DownloadFile"].ToString();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(uri));
int intChunkSize = 1048576; // 1 MB chunks
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
byte[] buffer = new byte[intChunkSize];
int intStatusCode = (int)response.StatusCode;
if (intStatusCode >= 200 && intStatusCode <= 299) // success
{
Stream sourceStream = response.GetResponseStream();
MemoryStream memStream = new MemoryStream();
int intBytesRead;
bool finished = false;
while (!finished)
{
intBytesRead= sourceStream.Read(buffer, 0, intChunkSize);
if (intBytesRead > 0)
{
memStream.Write(buffer, 0, intBytesRead);
// gather timing info here
}
else
{
finished = true;
}
}
}
}
}
The questions:
Does response contain all the data when it is instantiated, or just the header info? response.ContentLength does reflect the correct value.
Even though I am using a 1 MB chunk size, the actual bytes read (intBytesRead) in each iteration is much less, typically 16384 bytes (16 KB), but sometimes 1024 (1 KB). Why is this?
Is there any way to force it to actually read 1 MB chunks?
Does it serve any purpose here to actually write the data to the MemoryStream?
Thanks.
Dan
I want to download the first N Megabytes of huge XML File, so then I can close the broken tags with HTMLAgilityPack. Unfortunately, I can't use XMLReader.
I tried setting the Range on the HTTP Headers but that didn't seem to work, so now I'm trying this:
public string download(string url, int mb)
{
Int32 bytesToGet = 1048576 * mb;
HttpWebRequest request;
request = WebRequest.Create(url) as HttpWebRequest;
var buffer = new char[bytesToGet];
using (WebResponse response = request.GetResponse())
{
using (StreamReader sr = new StreamReader(response.GetResponseStream()))
{
sr.Read(buffer, 0, bytesToGet);
}
}
return new string(buffer);
}
but this still doesn't work either. I tried it with mb=5 and I get just a few lines of the XML file.
You're only calling Read() once, which doesn't promise to fill your buffer. Keep count of bytes downloaded and keep reading until your buffer is full or the end of the stream is reached:
int offset = 0;
int bytesRead = 0;
do
{
bytesRead = sr.Read(buffer, offset, bytesToGet - offset);
offset += bytesRead;
} while (bytesRead > 0);
I keep getting this error:
The specified argument is outside the range of valid values.
When I run this code in C#:
string sourceURL = "http://192.168.1.253/nphMotionJpeg?Resolution=320x240&Quality=Standard";
byte[] buffer = new byte[200000];
int read, total = 0;
// create HTTP request
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(sourceURL);
req.Credentials = new NetworkCredential("username", "password");
// get response
WebResponse resp = req.GetResponse();
// get response stream
// Make sure the stream gets closed once we're done with it
using (Stream stream = resp.GetResponseStream())
{
// A larger buffer size would be benefitial, but it's not going
// to make a significant difference.
while ((read = stream.Read(buffer, total, 1000)) != 0)
{
total += read;
}
}
// get bitmap
Bitmap bmp = (Bitmap)Bitmap.FromStream(new MemoryStream(buffer, 0, total));
pictureBox1.Image = bmp;
This line:
while ((read = stream.Read(buffer, total, 1000)) != 0)
Does anybody know what could cause this error or how to fix it?
Thanks in advance
Does anybody know what could cause this error?
I suspect total (or rather, total + 1000) has gone outside the range of the array - you'll get this error if you try to read more than 200K of data.
Personally I'd approach it differently - I'd create a MemoryStream to write to, and a much smaller buffer to read into, always reading as much data as you can, at the start of the buffer - and then copying that many bytes into the stream. Then just rewind the stream (set Position to 0) before loading it as a bitmap.
Or just use Stream.CopyTo if you're using .NET 4 or higher:
Stream output = new MemoryStream();
using (Stream input = resp.GetResponseStream())
{
input.CopyTo(output);
}
output.Position = 0;
Bitmap bmp = (Bitmap) Bitmap.FromStream(output);
I am developing c# application, in which i am downloading package(zip file) from server machine.It was downloading properly, but recently our package data has got some changes which is flex application.And by using c# we are downloading it into c drive or d drive.
Now with the new package i am facing some problem as
Unable to read data from the transport connection: An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.
My code is below
byte[] packageData = null;
packageData = touchServerClient.DownloadFile("/packages/" + this.PackageName);
public byte[] DownloadFile(string url)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(remoteSite.Url + url);
try
{
request.Method = "GET";
request.KeepAlive = false;
request.CookieContainer = new CookieContainer();
if (this.Cookies != null && this.Cookies.Count > 0)
request.CookieContainer.Add(this.Cookies);
HttpWebResponse webResponse = (HttpWebResponse)request.GetResponse();
// Console.WriteLine(response.StatusDescription);
Stream responseStream = webResponse.GetResponseStream();
int contentLength = Convert.ToInt32(webResponse.ContentLength);
byte[] fileData = StreamToByteArray(responseStream, contentLength);
return fileData;
}
public static byte[] StreamToByteArray(Stream stream, int initialLength)
{
// If we've been passed an unhelpful initial length, just
// use 32K.
if (initialLength < 1)
{
initialLength = 32768;
}
byte[] buffer = new byte[initialLength];
int read = 0;
int chunk;
while ((chunk = stream.Read(buffer, read, buffer.Length - read)) > 0)
{
read += chunk;
// If we've reached the end of our buffer, check to see if there's
// any more information
if (read == buffer.Length)
{
int nextByte = stream.ReadByte();
// End of stream? If so, we're done
if (nextByte == -1)
{
return buffer;
}
// Nope. Resize the buffer, put in the byte we've just
// read, and continue
byte[] newBuffer = new byte[buffer.Length * 2];
Array.Copy(buffer, newBuffer, buffer.Length);
newBuffer[read] = (byte)nextByte;
buffer = newBuffer;
read++;
}
}
// Buffer is now too big. Shrink it.
byte[] ret = new byte[read];
Array.Copy(buffer, ret, read);
return ret;
}
In the above function(StreamToByteArray) , i am getting error as
Unable to read data from the transport connection: An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.
Please help me on this, coz i am not supposed to change the code also.
Thanks in advance
Sangita
A few things to try:
Wrap your stream handling in a using statement.
This will clean up that resource.
using (Stream responseStream = webResponse.GetResponseStream())
{
int contentLength = Convert.ToInt32(webResponse.ContentLength);
byte[] fileData = StreamToByteArray(responseStream, contentLength);
return fileData;
}
Make sure there are no other heavy memory processes running on the same box. Particularly if they are making Socket-bound calls.
Try upping the value of the MaxUserPort registry value. Here is the article if you didn't see the link provided in the comments.