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How To Get Raw HttpWebRequest (c#)

We have a program that has been running for years making API calls to a web server using HttpWebRequest and yesterday it started giving an error (something like "connection forcibly closed by remote host"). The request works just fine when made through a web browser so I would love to be able to see the difference in requests. With the Firefox developer console, I can see the raw request that is made through the browser (that works) and I need to compare that to the http request that is made from our program. It seems like it should be simple (and very useful) to stream the request out to a string or a file so I can look at it (but I have not had any luck finding how to do that).
Can you tell me how to modify the below code to store the request that HttpWebRequest would send to a file or a string (instead of a network stream)?
public string Post(string uri, string data, string contentType, string method = "POST")
{
byte[] dataBytes = Encoding.UTF8.GetBytes(data);
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
request.ContentLength = dataBytes.Length;
request.ContentType = contentType;
request.Method = method;
using(Stream requestBody = request.GetRequestStream())
{
requestBody.Write(dataBytes, 0, dataBytes.Length);
}
using(HttpWebResponse response = (HttpWebResponse)request.GetResponse())
using(Stream stream = response.GetResponseStream())
using(StreamReader reader = new StreamReader(stream))
{
return reader.ReadToEnd();
}
}

You can't simply log the httprequest. Because you should also consider logging all the headers.
I suggest you to use some http sniffer to log the traffic(if you can't debug or modify your code)
In addition you can catch the exceptions by using WebException and get the raw error message from the server. Maybe it'll give you idea what the problem is.
catch (WebException ex)
{
using (var stream = ex.Response.GetResponseStream())
using (var reader = new StreamReader(stream))
{
var responseString = reader.ReadToEnd();
}
}

Debugging an HttpWebResponse

This is being done on a Windows Forms App. I've spent a ton of time stepping through this code with the debugger. What I've found are the following things and they all seem to be at this line:
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
1. If I include
request.SendChunked = true;
I get this error at the response line previously stated:
'System.Net.WebException: The remote server returned an error: (415) Unsupported Media Type.
2. If I comment out the code in #1, I receive this error at that main response line that I mentioned in the beginning:
'System.Net.WebException: The underlying connection was closed: The connection was closed unexpectedly.
3. If I go with route #1, the "Connection" of the request remains as "KeepAlive" all the way through. But if I go with route #2, the "Connection" of the request changes to "null" at the response line that I mentioned in the beginning.
private void HttpPost()
{
HttpWebRequest request = null;
Uri uri = new Uri("https://post.craigslist.org/bulk-rss/post");
request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
XmlDocument doc = new XmlDocument();
doc.Load("XMLFile1.xml");
//request.ContentLength = doc.InnerXml.Length;
request.SendChunked = true;
using (Stream writeStream = request.GetRequestStream())
{
UTF8Encoding encoding = new UTF8Encoding();
byte[] bytes = encoding.GetBytes(doc.InnerXml);
//request.ContentLength = bytes.Length;
writeStream.Write(bytes, 0, bytes.Length);
}
string result = string.Empty;
request.ProtocolVersion = System.Net.HttpVersion.Version11;
request.KeepAlive = false;
try
{
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
using (Stream responseStream = response.GetResponseStream())
{
using (System.IO.StreamReader readStream = new System.IO.StreamReader(responseStream, Encoding.UTF8))
{
result = readStream.ReadToEnd();
}
}
}
}
catch (Exception e)
{
string innerException = String.Format("Inner exception: '{0}'", e.Data);
string exceptionCause = String.Format("An error occurred: '{0}'", e);
System.IO.File.WriteAllText(#"C:\Users\Nathan\Documents\DebugOutputFile\exception.txt", exceptionCause);
System.IO.File.WriteAllText(#"C:\Users\Nathan\Documents\DebugOutputFile\innerException.txt", innerException);
}
}
I feel like these things are adding up towards a solution, but I could really use some guidance.

Option 1: Change your content type to match the body encoding
request.ContentType = "application/xml";
Option 2: Change your body encoding to match the specified content-type
If your server expects only "application/x-www-form-urlencoded", then you need to change your body encoding to suit it, for example, like this:
using (Stream writeStream = request.GetRequestStream())
{
UTF8Encoding encoding = new UTF8Encoding();
string response = String.Concat("arg=", HttpUtility.UrlEncode(doc.InnerXml))
byte[] bytes = encoding.GetBytes(doc.InnerXml);
//request.ContentLength = bytes.Length;
writeStream.Write(bytes, 0, bytes.Length);
}
You need to know the parameter name (above was set to "arg") and add a reference to System.Web, if you haven't.
See following XML...
<?xml version="1.0" encoding="UTF-8"?><test></test>
and encoded string for reference (your request body should look similar to this):
arg=%3C%3Fxml%20version%3D%221.0%22%20encoding%3D%22UTF-8%22%3F%3E%3Ctest%3E%3C%2Ftest%3E
Explanation
If you look at the response you are getting with the first approach: 415 - Unsupported Media Type, you can notice that the content type you are specifying ("application/x-www-form-urlencoded") doesn't match what you are sending in the body (an XML document). Chunk encoding should be enabled when sending files.
Note
When you are having trouble with a request done in source code, try to test the request alone with a web debugging tool, like Fiddler. There you would compose and issue the request until you get the response you want. Then you can compare that with what you are sending from source code (again you should use the same tool for inspecting your request).

HttpWebRequest.GetResponse() keeps getting timed out

i wrote a simple C# function to retrieve trade history from MtGox with following API call:
https://data.mtgox.com/api/1/BTCUSD/trades?since=<trade_id>
documented here: https://en.bitcoin.it/wiki/MtGox/API/HTTP/v1#Multi_currency_trades
here's the function:
string GetTradesOnline(Int64 tid)
{
Thread.Sleep(30000);
// communicate
string url = "https://data.mtgox.com/api/1/BTCUSD/trades?since=" + tid.ToString();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string json = reader.ReadToEnd();
reader.Close();
reader.Dispose();
response.Close();
return json;
}
i'm starting at tid=0 (trade id) to get the data (from the very beginning). for each request, i receive a response containing 1000 trade details. i always send the trade id from the previous response for the next request. it works fine for exactly 4 requests & responses. but after that, the following line throws a "System.Net.WebException", saying that "The operation has timed out":
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
here are the facts:
catching the exception and retying keeps causing the same exception
the default HttpWebRequest .Timeout and .ReadWriteTimeout are already high enough (over a minute)
changing HttpWebRequest.KeepAlive to false didn't solve anything either
it seems to always work in the browser even while the function is failing
it has no problems retrieveing the response from https://www.google.com
the amount of successful responses before the exceptions varies from day to day (but browser always works)
starting at the trade id that failed last time causes the exception immediately
calling this function from the main thread instead still caused the exception
running it on a different machine didn't work
running it from a different IP didn't work
increasing Thread.Sleep inbetween requests does not help
any ideas of what could be wrong?

I had the very same issue.
For me the fix was as simple as wrapping the HttpWebResponse code in using block.
using (HttpWebResponse response = (HttpWebResponse) request.GetResponse())
{
// Do your processings here....
}
Details: This issue usually happens when several requests are made to the same host, and WebResponse is not disposed properly. That is where using block will properly dispose the WebResponse object properly and thus solving the issue.

There are two kind of timeouts. Client timeout and server timeout. Have you tried doing something like this:
request.Timeout = Timeout.Infinite;
request.KeepAlive = true;
Try something like this...

I just had similar troubles calling a REST Service on a LINUX Server thru ssl. After trying many different configuration scenarios I found out that I had to send a UserAgent in the http head.
Here is my final method for calling the REST API.
private static string RunWebRequest(string url, string json)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
// Header
request.ContentType = "application/json";
request.Method = "POST";
request.AllowAutoRedirect = false;
request.KeepAlive = false;
request.Timeout = 30000;
request.ReadWriteTimeout = 30000;
request.UserAgent = "test.net";
request.Accept = "application/json";
request.ProtocolVersion = HttpVersion.Version11;
request.Headers.Add("Accept-Language","de_DE");
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
byte[] bytes = Encoding.UTF8.GetBytes(json);
request.ContentLength = bytes.Length;
using (var writer = request.GetRequestStream())
{
writer.Write(bytes, 0, bytes.Length);
writer.Flush();
writer.Close();
}
var httpResponse = (HttpWebResponse)request.GetResponse();
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
var jsonReturn = streamReader.ReadToEnd();
return jsonReturn;
}
}

This is not a solution, but just an alternative:
These days i almost only use WebClient instead of HttpWebRequest. Especially WebClient.UploadString for POST and PUT and WebClient.DownloadString. These simply take and return strings. This way i don't have to deal with streams objects, except when i get a WebException. i can also set the content type with WebClient.Headers["Content-type"] if necessary. The using statement also makes life easier by calling Dispose for me.
Rarely for performance, i set System.Net.ServicePointManager.DefaultConnectionLimit high and instead use HttpClient with it's Async methods for simultaneous calls.
This is how i would do it now
string GetTradesOnline(Int64 tid)
{
using (var wc = new WebClient())
{
return wc.DownloadString("https://data.mtgox.com/api/1/BTCUSD/trades?since=" + tid.ToString());
}
}
2 more POST examples
// POST
string SubmitData(string data)
{
string response;
using (var wc = new WebClient())
{
wc.Headers["Content-type"] = "text/plain";
response = wc.UploadString("https://data.mtgox.com/api/1/BTCUSD/trades", "POST", data);
}
return response;
}
// POST: easily url encode multiple parameters
string SubmitForm(string project, string subject, string sender, string message)
{
// url encoded query
NameValueCollection query = HttpUtility.ParseQueryString(string.Empty);
query.Add("project", project);
query.Add("subject", subject);
// url encoded data
NameValueCollection data = HttpUtility.ParseQueryString(string.Empty);
data.Add("sender", sender);
data.Add("message", message);
string response;
using (var wc = new WebClient())
{
wc.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
response = wc.UploadString( "https://data.mtgox.com/api/1/BTCUSD/trades?"+query.ToString()
, WebRequestMethods.Http.Post
, data.ToString()
);
}
return response;
}
Error handling
try
{
Console.WriteLine(GetTradesOnline(0));
string data = File.ReadAllText(#"C:\mydata.txt");
Console.WriteLine(SubmitData(data));
Console.WriteLine(SubmitForm("The Big Project", "Progress", "John Smith", "almost done"));
}
catch (WebException ex)
{
string msg;
if (ex.Response != null)
{
// read response HTTP body
using (var sr = new StreamReader(ex.Response.GetResponseStream())) msg = sr.ReadToEnd();
}
else
{
msg = ex.Message;
}
Log(msg);
}

For what it's worth, I was experiencing the same issues with timeouts every time I used it, even though calls went through to the server I was calling. The problem in my case was that I had Expect set to application/json, when that wasn't what the server was returning.

"Request timed out" when makinng two HttpWebRequests to the same Java server from C# over .NET Compact

I have a client application running on C# on a .NETCF 3.5 device POSTing to a Java servlet located remotely. I am receiving a "Request Timed out" during my third HTTP POST to the same servlet. For example, if the servlet manages login to our Java server, the first two login attempts from the client would go through (same client device) and when I attempt the third one, it will return in a "Request timed out" exception from the server. I have noticed this happen always and I can't figure out the problem. I read that C# by default sends the Request 100 continue in the HTTP headers so I used the ServicePointManager to set the request 100 to false to no avail.
Here is the code that is throwing this error:
serverUrl = url;
string responseFromServer = "";
try
{
System.Net.ServicePointManager.Expect100Continue = false;
int tmp = ServicePointManager.DefaultConnectionLimit;
// Create a request using a URL that can receive a post.
request = (HttpWebRequest)WebRequest.Create(url);
// Set the Method property of the request to POST.
request.Method = "POST";
// Create POST data and convert it to a byte array.
byte[] byteArray = System.Text.Encoding.UTF8.GetBytes(url);
// Set the ContentType property of the WebRequest.
request.ContentType = "application/x-www-form-urlencoded";
// Set the ContentLength property of the WebRequest.
request.ContentLength = byteArray.Length;
request.Timeout = (50 * 100);
request.Proxy = System.Net.GlobalProxySelection.GetEmptyWebProxy();
// Get the request stream.
Stream dataStream = request.GetRequestStream();
// Write the data to the request stream.
dataStream.Write(byteArray, 0, byteArray.Length);
// Close the Stream object.
dataStream.Close();
// Get the response.
response = (HttpWebResponse)request.GetResponse();
// Get the stream containing content returned by the server.
dataStream = response.GetResponseStream();
// Open the stream using a StreamReader for easy access.
StreamReader reader = new StreamReader(dataStream);
// Read the content.
responseFromServer = reader.ReadToEnd();
// Clean up the streams.
reader.Close();
dataStream.Close();
response.Close();
return responseFromServer;
}
catch (Exception WebExp)
{
Logging.Instance.Log(Logging.Levels.Error, "Error in DoPost while retrieving : "+url+ " " + WebExp.Message.ToString());
Logging.Instance.Log(Logging.Levels.Error, WebExp.StackTrace.ToString());
throw WebExp;
}
Any help would be much appreciated. Thanks!

This behaviour is due to wrong Exception handling regarding to the WebResponse. You have always to handle the response and close it. Otherwise the third attempt of HTTP Webrequest will fail with timeout which is limited by WinCE.
Following source code will be safe:
HttpWebResponse response = null;
try
{
//...
response = (HttpWebResponse)request.GetResponse();
//...
}
catch(Exception e)
{
// logging, etc.
throw e;
}
finally
{
if(response!=null)
{
response.Close();
}
}

500 internal server error at GetResponse()

I have a heavy traffic aspx page calling a web service upon every user`s request as follows.
string uri = "Path.asmx";
string soap = "soap xml string";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Headers.Add("SOAPAction", "\"http://xxxxxx"");
request.ContentType = "text/xml;charset=\"utf-8\"";
request.Accept = "text/xml";
request.Method = "POST";
using (Stream stm = request.GetRequestStream())
{
using (StreamWriter stmw = new StreamWriter(stm))
{
stmw.Write(soap);
}
}
WebResponse response = request.GetResponse();
response.close();
Everything is working fine but sometimes I am getting the following error.
The remote server returned an error: (500) Internal Server Error.
at System.Net.HttpWebRequest.GetResponse()
Does anybody have any idea about this error or can anybody tell me if I am doing wrong.

For me this error occurred because I had 2 web API actions that had the exact same signatures and both had the same verbs, HttpPost, what I did was change one of the verbs (the one used for updating) to PUT and the error was removed. The following in my catch statement helped in getting to the root of the problem:
catch (WebException webex)
{
WebResponse errResp = webex.Response;
using (Stream respStream = errResp.GetResponseStream())
{
StreamReader reader = new StreamReader(respStream);
string text = reader.ReadToEnd();
}
}

From that error, I would say that your code is fine, at least the part that calls the webservice. The error seems to be in the actual web service.
To get the error from the web server, add a try catch and catch a WebException. A WebException has a property called Response which is a HttpResponse. you can then log anything that is returned, and upload you code. Check back later in the logs and see what is actually being returned.

Finally I get rid of internal server error message with the following code. Not sure if there is another way to achieve it.
string uri = "Path.asmx";
string soap = "soap xml string";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Headers.Add("SOAPAction", "\"http://xxxxxx"");
request.ContentType = "text/xml;charset=\"utf-8\"";
request.Accept = "text/xml";
request.Method = "POST";
using (Stream stm = request.GetRequestStream())
{
using (StreamWriter stmw = new StreamWriter(stm))
{
stmw.Write(soap);
}
}
using (WebResponse webResponse = request.GetResponse())
{
}

Have you tried to specify UserAgent for your request? For example:
request.UserAgent = "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)";

looking at your error message first of all I would suggest you to recompile your whole application, make sure all the required dlls are there in bin folder when you recompile it.

In my case my request object inherited from base object. Without knowingly I added a property with int? in my request object and my base object also has same property ( same name ) with int datatype. I noticed this and deleted the property which I added in request object and after that it worked fine.

For me the error was misleading. I discovered the true error by testing the errant web service with SoapUI.

In my case I just remove the SoapAction instruction from the HttpWebRequest object. So, I don't define .Headers.Add("SOAPAction","someurl") in HttpWebRequest definitions and my code works fine.
ResultXML is an XDocument.
ResultString is a string.
try
{
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Url);
//req.Headers.Add("SOAPAction", "http://tempuri.org/IWebService/GetMessage");
req.ProtocolVersion = HttpVersion.Version11;
req.ContentType = "text/xml;charset=\"utf-8\"";
req.Accept = "text/xml";
req.KeepAlive = true;
req.Method = "POST";
using (Stream stm = req.GetRequestStream())
{
using (StreamWriter stmw = new StreamWriter(stm))
stmw.Write(soapStr);
}
using (StreamReader responseReader = new StreamReader(req.GetResponse().GetResponseStream()))
{
string result = responseReader.ReadToEnd();
ResultXML = XDocument.Parse(result);
ResultString = result;
}
}