Develop Reference

download file on client-side sent in response of API

I have a task to download whatever file is sent in the response of my API call, Possible extensions are zip, pdf and doc. I just have the API endpoints to download those files returned in the response, no idea about server side code.
The task is not to write or create those files on server and then transmit to local, but need to download it directly on the client side.
I have written a web method which calls the API on click of button and gets the response stream, the code written also downloads the required file correctly , but those downloaded files never open. they are either corrupted or damaged.
Below is my code to download and write the file on client side.
Any idea what is possibly going wrong, or how can i download the files correctly.
Note: This aren't very large files, the max size possibly could be 50Mb or so.
Not sure, what all things from stack overflow i have tried so far, but no luck was for sure.
public string CallService(string hbno)
{
try
{
var httpWebRequest = (HttpWebRequest)WebRequest.Create("URL");
httpWebRequest.ContentType = "application/json";
httpWebRequest.Method = "POST";
DataTable dt = GetPrintLogData(hbno);
if (dt != null && dt.Rows.Count > 0)
{
using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
{
string json = _Serializer.Serialize(body);
streamWriter.Write(json);
streamWriter.Flush();
streamWriter.Close();
}
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
using (var resp = (HttpWebResponse)httpWebRequest.GetResponse())
{
using (var stream = resp.GetResponseStream())
{
if (resp.StatusCode == HttpStatusCode.OK)
{
var cd = new ContentDisposition(resp.Headers["Content-Disposition"]);
StreamToFileAttachment(stream, cd.FileName);
return "successful";
}
else
{
return "Something went wrong";
}
}
}
}
else { return "No match found in database"; }
}
catch (Exception ex)
{
throw;
}
}
public static byte[] ReadFully2(Stream stream)
{
try
{
byte[] buffer = new byte[32768]; //set the size of your buffer (chunk)
using (MemoryStream ms = new MemoryStream()) //You need a db connection instead
{
while (true) //loop to the end of the file
{
int read = stream.Read(buffer, 0, buffer.Length); //read each chunk
if (read <= 0)
{
var test = ms.ToArray().Length;
//check for end of file
return ms.ToArray();
}
else
{
ms.Write(buffer, 0, read); //write chunk to [wherever]
}
}
}
}
catch (Exception ex)
{
//throw;
}
}
static void StreamToFileAttachment(Stream str, string fileName)
{
try
{
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
var length = ReadFully2(str).Length;
byte[] buf = new byte[length]; //declare arraysize
str.Read(buf, 0, buf.Length);
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);
HttpContext.Current.Response.AddHeader("Content-Length", length.ToString());
HttpContext.Current.Response.ContentType = GetMimeTypeByFileName(fileName);
HttpContext.Current.Response.OutputStream.Write(buf, 0, buf.Length);
HttpContext.Current.Response.Flush(); // Sends all currently buffered output to the client.
HttpContext.Current.Response.SuppressContent = true; // Gets or sets a value indicating whether to send HTTP content to the client.
HttpContext.Current.ApplicationInstance.CompleteRequest(); // Causes ASP.NET to bypass all events and filtering in the HTTP pipeline chain of execution and directly execute the EndRequest event.
// HttpContext.Current.Response.End();
}
catch (Exception ex)
{
//throw;
}
}

How do I copy a HttpRequest to another web service?

I have two identical web services currently installed on the same PC for testing purposes. A request that is received by the first service, is suposed go to the second one as well. My intention was to do this using a HttpModule. I handle the request during application.BeginRequest.
public void AsyncForwardRequest(HttpRequest request)
{
try
{
// Prepare web request...
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(WSaddress);
req.Credentials = CredentialCache.DefaultCredentials;
req.Headers.Add("SOAPAction", request.Headers["SOAPAction"]);
req.ContentType = request.Headers["Content-Type"];
req.Accept = request.Headers["Accept"];
req.Method = request.HttpMethod;
// Send the data.
long posStream = request.InputStream.Position;
long len = request.InputStream.Length;
byte[] buff = new byte[len];
request.InputStream.Seek(0, SeekOrigin.Begin);
if (len < int.MaxValue && request.InputStream.Read(buff, 0, (int)len) > 0)
{
using (Stream stm = req.GetRequestStream())
{
stm.Write(buff, 0, (int)len);
}
request.InputStream.Position = posStream;
DebugOutputStream(request.InputStream);
request.InputStream.Seek(0, SeekOrigin.Begin);
IAsyncResult result = (IAsyncResult)req.BeginGetResponse(new AsyncCallback(RespCallback), req);
}
}
catch (Exception ex)
{
App.Error2(String.Format("RequestDuplicatorModule - BeginRequest; ERROR begin request: {0}", ex.Message), ex);
}
private static void RespCallback(IAsyncResult asynchronousResult)
{
try
{
// State of request is asynchronous.
var req = (HttpWebRequest)asynchronousResult.AsyncState;
WebResponse resp = (HttpWebResponse)req.EndGetResponse(asynchronousResult);
Stream responseStream = resp.GetResponseStream();
System.IO.Stream stream = responseStream;
Byte[] arr = new Byte[1024 * 100];
stream.Read(arr, 0, 1024 * 100);
if (arr.Length > 0)
{
string body = (new ASCIIEncoding()).GetString(arr);
Debug.Print(body);
}
}
catch (WebException ex)
{
App.Error2(String.Format("RequestDuplicatorModule - BeginRequest; ERROR begin request: {0}", ex.Message), ex);
}
}
This (HttpWebResponse)req.EndGetResponse(asynchronousResult) throws an exception: 500 Internal Server Error and fails. The original request goes through fine.
request.InnerStream:
...
Does this have anything to do with the web service addresses being different? In my case they're:
http://localhost/WS/service.asmx
http://localhost/WS_replicate/service.asmx

I would at least implement this, to be able to read the content of a httpwebrequest that has a status 500:
catch (WebException ex)
{
HttpWebResponse webResponse = (HttpWebResponse)ex.Response;
Stream dataStream = webResponse.GetResponseStream();
if (dataStream != null)
{
StreamReader reader = new StreamReader(dataStream);
response = reader.ReadToEnd();
}
}
Not answering your question though, i would suggest having a simple amsx that reads the request, and posts the request to the two different web services. If you need some code for that let me know.
Additional advantages would be that the asmx will be easier to support for the developer as well as the one dealing with the deployment. You could add configuration options to make the actual url's dynamic.

Was able to modify the AsyncForwardRequest method so that I can actually edit the SoapEnvelope itself:
string buffString = System.Text.UTF8Encoding.UTF8.GetString(buff);
using (Stream stm = req.GetRequestStream())
{
bool stmIsReadable = stm.CanRead; //false, stream is not readable, how to get
//around this?
//solution: read Byte Array into a String,
//modify <wsa:to>, write String back into a
//Buffer, write Buffer to Stream
buffString = buffString.Replace("http://localhost/WS/Service.asmx", WSaddress);
//write modded string to buff
buff = System.Text.UTF8Encoding.UTF8.GetBytes(buffString);
stm.Write(buff, 0, (int)buff.Length);
}

Sending image with HttpListener only working for some images

I'm trying create a small http proxy service. This is not working so well. It is able to serve HTML okayish, however it chokes up on images. That is, some images.
Sending in a url through my proxy yields 19.4 kb in the response (according to firebug)
Visiting that url directly also yields 19.4 kb in the response, again according to firebug. The difference is, it doesn't show up when I put it through my proxy, but it does when I browse directly.
A completely different url works just fine. Does anyone have any idea?
private void DoProxy()
{
var http = listener.GetContext();
string url = http.Request.QueryString["url"];
WebRequest request = HttpWebRequest.Create(url);
WebResponse response = request.GetResponse();
http.Response.ContentType = response.ContentType;
byte[] content;
using (Stream responseStream = response.GetResponseStream())
content = ReadAll(responseStream);
http.Response.ContentLength64 = content.Length;
http.Response.OutputStream.Write(content, 0, content.Length);
http.Response.Close();
}
private byte[] ReadAll(Stream stream)
{
IList<byte> array = new List<byte>();
int b;
while ((b = stream.ReadByte()) != -1)
array.Add(Convert.ToByte(b));
return array.ToArray();
}

I would try and flush/close the OutputStream before you close the response.
Also as a second suggestion have a look at the HTTP traffic from the original site and then through your proxy site using an HTTP debugger like Fiddler - there must be a difference when using your proxy.
Also to make the ReadAll method more effective, in general I would avoid to load the full content into memory, because this will blow up on huge files - just stream them directly from the input stream to the output stream. If you still want to use byte arrays consider the following (untested but should work):
private byte[] ReadAll(Stream stream)
{
byte[] buffer = new byte[8192];
int bytesRead = 1;
List<byte> arrayList = new List<byte>();
while (bytesRead > 0)
{
bytesRead = stream.Read(buffer, 0, buffer.Length);
arrayList.AddRange(new ArraySegment<byte>(buffer, 0, bytesRead).Array);
}
return arrayList.ToArray();
}

You can try to replace
http.Response.Close();
with
http.Response.Flush();
http.Response.End();

A problem could be that you don't specify the MIME type of the response. Browsersthese days are very forgiving, but maybe there is a circumstance where the browser doesn't know how to handle whatever you are sticking through its throat.
I have written the most smallish file-based http server, presented here, which as far as I can remember can serve images without much problem.

Just separate the text response and image response, and write the outputs separately. I did like below and it worked for me.
static void Main(string[] args)
{
HttpListener server = new HttpListener();
server.Prefixes.Add("http://localhost:9020/");
server.Start();
Console.WriteLine("Listening...");
while (true)
{
try
{
HttpListenerContext context = server.GetContext();
HttpListenerResponse response = context.Response;
String localpath = context.Request.Url.LocalPath;
string page = Directory.GetCurrentDirectory() + localpath;
string msg = "";
bool imgtest = false;
if (localpath == "/")
page = "index.html";
Console.WriteLine(localpath);
if (!page.Contains("jpg") && !page.Contains("png"))//Separates image request
{
TextReader tr = new StreamReader(page);
msg = tr.ReadToEnd();
tr.Dispose();
}
else
{
byte[] output = File.ReadAllBytes(page);
response.ContentLength64 = output.Length;
Stream st1 = response.OutputStream;
st1.Write(output, 0, output.Length);
imgtest = true;
}
if (imgtest==false)
{
byte[] buffer = Encoding.UTF8.GetBytes(msg);
response.ContentLength64 = buffer.Length;
Stream st = response.OutputStream;
st.Write(buffer, 0, buffer.Length);
context.Response.Close();
}
}
catch (Exception ex)
{
Console.WriteLine("Error: "+ex);
Console.ReadKey();
}
}

FtpWebRequest closing the upload stream hangs on large files

I am trying to use an FtpWebRequest to upload some files. This works for smallish files (say <2MB), but when I am trying to load a 16MB file, the files uploads successfully, but when I call request.GetRequestStream().Close, the code hangs (or timesout if the timeout is low enough).
I could just a) not close it and b)not bother to get the response from the server, but that doesn't seem right! See code below (using SSL or not, the same problem occurs.)
output.Close() is the line that hangs....
public static void SendFileViaFtp(string file, string url, bool useSsl, ICredentials credentials)
{
var request = (FtpWebRequest)WebRequest.Create(url + Path.GetFileName(file));
request.EnableSsl = useSsl;
request.UseBinary = true;
request.Credentials = credentials;
request.Method = WebRequestMethods.Ftp.UploadFile;
request.Timeout = 10000000;
request.ReadWriteTimeout = 10000000;
request.KeepAlive = true;
var input = File.Open(file, FileMode.Open);
var output = request.GetRequestStream();
var buffer = new byte[1024];
var lastBytesRead = -1;
var i = 0;
while (lastBytesRead != 0)
{
i++;
lastBytesRead = input.Read(buffer, 0, 1024);
Debug.WriteLine(lastBytesRead + " " + i);
if (lastBytesRead > 0)
{
output.Write(buffer, 0, lastBytesRead);
}else
{
Debug.WriteLine("Finished");
}
}
input.Close();
output.Close();
var response = (FtpWebResponse)request.GetResponse();
response.Close();
}
Thanks,

try
// after finished uploading
request.Abort(); // <=== MAGIC PART
// befor response.Close()
var response = (FtpWebResponse)request.GetResponse();
response.Close();
taken from here

try to close output before input.
make sure the last buffer isn't to large, or you could write a few empty bytes.
I don't know if it's necessary but i always set the request contentlength to the inputfile-length.
Here is an good example: http://dotnet-snippets.de/dns/ftp-file-upload-mit-buffer-SID886.aspx

KeepAliveException when using HttpWebRequest.GetResponse

I am trying to POST an attachment to CouchDB using the HttpWebRequest. However, when I attempt "response = (HttpWebResponse)httpWebRequest.GetResponse();" I receive a WebException with the message "The underlying connection was closed: A connection that was expected to be kept alive was closed by the server."
I have found some articles stating that setting the keepalive to false and httpversion to 1.0 resolves the situation. I am finding that it does not yeilding the exact same error, plus I do not want to take that approach as I do not want to use the 1.0 version due to how it handles the connection.
Any suggestions or ideas are welcome. I'll try them all until one works!
public ServerResponse PostAttachment(Server server, Database db, Attachment attachment)
{
Stream dataStream;
HttpWebResponse response = null;
StreamReader sr = null;
byte[] buffer;
string json;
string boundary = "----------------------------" + DateTime.Now.Ticks.ToString("x");
string headerTemplate = "Content-Disposition: form-data; name=\"_attachments\"; filename=\"" + attachment.Filename + "\"\r\n Content-Type: application/octet-stream\r\n\r\n";
byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(headerTemplate);
byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create("http://" + server.Host + ":" +
server.Port.ToString() + "/" + db.Name + "/" + attachment.Document.Id);
httpWebRequest.ContentType = "multipart/form-data; boundary=" + boundary;
httpWebRequest.Method = "POST";
httpWebRequest.KeepAlive = true;
httpWebRequest.ContentLength = attachment.Stream.Length + headerbytes.Length + boundarybytes.Length;
if (!string.IsNullOrEmpty(server.EncodedCredentials))
httpWebRequest.Headers.Add("Authorization", server.EncodedCredentials);
if (!attachment.Stream.CanRead)
throw new System.NotSupportedException("The stream cannot be read.");
// Get the request stream
try
{
dataStream = httpWebRequest.GetRequestStream();
}
catch (Exception e)
{
throw new WebException("Failed to get the request stream.", e);
}
buffer = new byte[server.BufferSize];
int bytesRead;
dataStream.Write(headerbytes,0,headerbytes.Length);
attachment.Stream.Position = 0;
while ((bytesRead = attachment.Stream.Read(buffer, 0, buffer.Length)) > 0)
{
dataStream.Write(buffer, 0, bytesRead);
}
dataStream.Write(boundarybytes, 0, boundarybytes.Length);
dataStream.Close();
// send the request and get the response
try
{
response = (HttpWebResponse)httpWebRequest.GetResponse();
}
catch (Exception e)
{
throw new WebException("Invalid response received from server.", e);
}
// get the server's response json
try
{
dataStream = response.GetResponseStream();
sr = new StreamReader(dataStream);
json = sr.ReadToEnd();
}
catch (Exception e)
{
throw new WebException("Failed to access the response stream.", e);
}
// close up all our streams and response
sr.Close();
dataStream.Close();
response.Close();
// Deserialize the server response
return ConvertTo.JsonToServerResponse(json);
}

After a considerable amount of research on the topic, I have decided to use PUT. While Futon uses the POST method, it is undocumented. For anyone reading this in the future, use the PUT method, it will make your life much easier.