Develop Reference

GDax API GET request always returns Error 400

I'm trying to get the order book from GDAX (link to documentation of the call) but when doing it from the c# executable I always get Error 400 - Bad request.
When taking the actual URL and pasting it into my browser, it works fine.
String URL = "https://api.gdax.com/products/BTC-USD/book?level=2";
WebRequest request = WebRequest.Create(URL);
WebResponse response = request.GetResponse();

The actual issue with your API call is , the API is expecting a user-agent string while making the request: Below is the code in working condition:
try
{
String URL = "http://api.gdax.com/products/BTC-USD/book?level=2";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.UserAgent = ".NET Framework Test Client";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
var encoding = ASCIIEncoding.ASCII;
using (var reader = new System.IO.StreamReader(response.GetResponseStream(), encoding))
{
string responseText = reader.ReadToEnd();
}
}
catch(WebException ex)
{
HttpWebResponse xyz = ex.Response as HttpWebResponse;
var encoding = ASCIIEncoding.ASCII;
using (var reader = new System.IO.StreamReader(xyz.GetResponseStream(), encoding))
{
string responseText = reader.ReadToEnd();
}
}
Basically ProtocolError indicates that you have received the response but there is an error related to protocol, which you can observe, when you read the response content from exception. I have added catch to handle the exception and read ex.Response (which is HttpWebResponse) and could see that the API is asking for user-agent to be suppllied while making the call. I got to see the error as "{"message":"User-Agent header is required."}"
You can ignore the code inside the exception block, I used it only to see what is the actual response message, which contains actual error details
Note: I have boxed WebRequest to HttpWebRequest to have additional http protocol related properties and most importantly "UserAgent" property which is not available with the WebRequest class.

You need to Accept the certificarte, Google for access to a https webrequest.
Like this

Consuming Twitters 1.1 API using OAuth, getting no response and it happens instantly

I am trying to swap my website over to consuming the new Twitter 1.1 API with uses OAuth 1.0a. I am able to get the correct response using a REST client and I am now trying to duplicate that on my website using c#.
I have constructed my headers the appropriate way and I have verified that they are in the correct format for what Twitter is looking for.
The issue I am having is that I do not think I am actually sending the request. I say this because my application returns almost instantly. The request should take a second or so to send at least, and my response has totally empty, with no 401 or 400 status code.
Below I have the code that actually sends the request. I am actually sending the request and if so why am I not getting any status code or anything.
Thanks in advance for the help.
//string url = "https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name=MYSCREENNAME&count=2";
string url = "https://api.twitter.com/1.1/statuses/user_timeline.json";
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.Method = "GET";
webRequest.Headers.Add("Authorization", authorizationHeaderParams);
try {
var response = webRequest.GetResponse() as HttpWebResponse;
if (response != null && response.StatusCode != HttpStatusCode.OK) {
lblresponse.InnerText = "The request did not complete and returned status code: {0} " + response.StatusCode;
}
if (response != null) {
var reader = new StreamReader(response.GetResponseStream());
reader.ReadToEnd();
lblresponse.InnerText += "success";
}
} catch {
lblresponse.InnerText += "fail";
}
So yeah this code goes straight to the catch block. My thoughts are I am not actually sending the request, since it takes no time to happen. I know there are some libraries designed to make this easier but I would much rather learn how to do it myself (with the help of you guys).
Thanks.

The request is going to throw an exception in the case of a 400 or 401. So catch System.Web.Exception in the catch block to see if there's a 400 or 401.
catch(System.Web.Exception ex) {
var errorReponse = (HttpWebResponse)ex.Response;
var statusCode = errorReponse.StatusCode;
lblresponse.InnerText += "fail";
}

System.Net.WebException

is seems to me that WebRequest.Create(url) fails a litle to soon..
Explanations:
on a url that it failed (or throwed a System.Net.WebException) ... copy-paste -ing that url into the browser seems to work..browser gives response!.. sometimes with a remarcable delay (~10 seconds).. but WebRequest in less than 3 seconds throws exception
Example of valid url on which it fails:
http://tracker.podtropolis.com:2710/announce?info_hash=%92%FD%2F%0B%40%F64%C5%86%19%D6%3E%B1%28%B2%81%A1J%D4%F6&peer_id=-AZ2060-%AD%18%05o%11%A6%26%B3%C3%D16%AC&port=6881&downloaded=0&uploaded=0&left=647749313&numwant=30&compact=1&event=started
if it has any meaning firefox reacts 10 times more slowly on this url that explorer, also sometimes firefox crashes on loading such a url
So question Why is WebRequest failing so soon?? I would like it to try a litle harder to get response from URL...
And this is the method that catches exeption (here i check if url is valid OR ~ "is tracker alive??")
public static bool isURLValid(string url)
{
try
{
HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
request.Method = "HEAD";
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
//Returns TURE if the Status code == 200
return (response.StatusCode == HttpStatusCode.OK);
}
catch (Exception ex) //(WebException ex)
{
Logger.e(TAG, "isURLValid", ex);
return false; //Any exception will returns false.
}
}
if valid i get stream (i know .. I know ..double contact.. but still)
inputStream = WebRequest.Create(fullURL).GetResponse().GetResponseStream();
So.. thoughts?

How to ignore 401 unauthorized error from webrequest to get website status

I am writing an application to check the status of some internal web applications. Some of these applications use Windows authentication. When I use this code to check the status, it throws The remote server returned an error: (401) Unauthorized.. Which is understandable because I haven't provided any credentials to the webiste so I am not authorized.
WebResponse objResponse = null;
WebRequest objRequest = HttpWebRequest.Create(website);
objResponse = objRequest.GetResponse();
Is there a way to ignore the 401 error without doing something like this?
WebRequest objRequest = HttpWebRequest.Create(website);
try
{
objResponse = objRequest.GetResponse();
}
catch (WebException ex)
{
//Catch and ignore 401 Unauthorized errors because this means the site is up, the app just doesn't have authorization to use it.
if (!ex.Message.Contains("The remote server returned an error: (401) Unauthorized."))
{
throw;
}
}

I would suggest to try this:
try
{
objResponse = objRequest.GetResponse() as HttpWebResponse;
}
catch (WebException ex)
{
objResponse = ex.Response as HttpWebResponse;
}
finally
The WebException has the response all information you want.

When the server is down or unreachable you will get a timeout exception. I know that the only way to handle that is with a try/catch.
I'm quite sure this is the case for most errors (401/404/501), so: No, you can't ignore (prevent) the exceptions but you will have to handle them. They are the only way to get most of the StatusCodes your App is looking for.

The short of it is you'll want to check the myHttpWebResponse.StatusCode for the status code and act accordingly.
Sample code from reference:
public static void GetPage(String url)
{
try
{
// Creates an HttpWebRequest for the specified URL.
HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(url);
// Sends the HttpWebRequest and waits for a response.
HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
if (myHttpWebResponse.StatusCode == HttpStatusCode.OK)
Console.WriteLine("\r\nResponse Status Code is OK and StatusDescription is: {0}",
myHttpWebResponse.StatusDescription);
// Releases the resources of the response.
myHttpWebResponse.Close();
}
catch(WebException e)
{
Console.WriteLine("\r\nWebException Raised. The following error occured : {0}",e.Status);
}
catch(Exception e)
{
Console.WriteLine("\nThe following Exception was raised : {0}",e.Message);
}
}

How do I get headers from a 401 Server Error

I'm writing a port scanner to detect web services running on the local network. Some of these web services require basic authentication - I don't know the username/ password for these services, I just want to list them, so I can't provide the credentials at this stage. I'm using the code:
var request = (HttpWebRequest)WebRequest.Create("http://" + req);
request.Referer = "";
request.Timeout = 3000;
request.UserAgent = "Mozilla/5.0";
request.AllowAutoRedirect = false;
request.Method = WebRequestMethods.Http.Head;
HttpWebResponse response = null;
try
{
response = (HttpWebResponse) request.GetResponse();
// I want to parse the headers here for the server name but as the exception is thrown the response object is null.
}
catch (Exception ex)
{
//401 error is caught here - response is null
}
I'm then parsing out the server name from the headers that are returned - I know they are being returned because I can see them with fiddler but the HttpWebResponse object is set to null as the GetResponse() method is throwing an exception. Basically - how do I get it to not throw and exception but return the headers along with a status code of 401.

If you catch a WebException you'll have access to ex.Response and you can retrieve your headers from there.