I have a problem with httpwebrequest exception. I use the following code to make a request and catch the exception.
try
{
Uri url= new Uri("https://www.example.com");
HttpWebRequest request2 =(HttpWebRequest)WebRequest.Create(url);
request2.Timeout = 10000;
HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse();
response2.Close();
}
catch (TimeoutException)
{
listBox.Items.Insert(0, "Timeout");
}
catch (WebException ex)
{
using (WebResponse response = ex.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)response;
listBox.Items.Insert(0, "Status code(Benchmark):" + httpResponse.StatusCode);
}
}
catch
{
listBox.Items.Insert(0, "Failure");
}
At company network when I enter a non-existing url such as www.oiuahsdupiasduiuhid.com; it throws webexception . I got status code: not found or service unavailable. However If I try it at home, it doesn't throw any exception. It waits around 1 second and then without any error stops working. I delete all exceptions to see what is happening but the problem is it doesn’t show any error.
Do you have any idea about what is the problem?
Or any recommendation, how can I handle this problem with a different way?
Without knowing more about your application design, specifically exception handling further up the call stack, it is hard to say why it is behaving like it is when you are at home.
But when I just tried your exact code, it did throw a WebException, however httpResponse.StatusCode throws a NullReferenceException because httpResponse is null. If you are potentially swallowing this exception further up the call stack, it could explain the situation you are seeing.
httpResponse is going to be null in many WebException cases because your request did not receive any response, specifically in the timeout scenario.
Before casting WebException.Response, you need to check the WebException.Status property. If that status suggests a response was received, then you can go check WebException.Response, otherwise it is just going to be null. Try something like:
if(e.Status == WebExceptionStatus.ProtocolError) {
listBox.Items.Insert("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
}
else
{
listBox.Items.Insert("Status : {0}", ex.Status);
}
As a side note, your response2.Close(); is never going to be called when HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse(); throws an exception, so you should be wrapping it in a using block:
using(HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse())
{
// do something with response
}
Thanks to psubsee2003. I got my answer. here is my code which is working properly. I added following codes to webexception.
if (ex.Status == WebExceptionStatus.ProtocolError)
{
using (WebResponse response = ex.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)response;
listBox2.Items.Insert(0, "Status:" + httpResponse.StatusCode);
}
}
else
{
listBox2.Items.Insert(0, "Status: " + ex.Status);
}
Related
I am initiating an HttpWebRequest and then retrieving it's response. Occasionally, I get a 500 (or at least 5##) error, but no description. I have control over both endpoints and would like the receiving end to get a little bit more information. For example, I would like to pass the exception message from server to client. Is this possible using HttpWebRequest and HttpWebResponse?
Code:
try
{
HttpWebRequest webRequest = HttpWebRequest.Create(URL) as HttpWebRequest;
webRequest.Method = WebRequestMethods.Http.Get;
webRequest.Credentials = new NetworkCredential(Username, Password);
webRequest.ContentType = "application/x-www-form-urlencoded";
using(HttpWebResponse response = webRequest.GetResponse() as HttpWebResponse)
{
if(response.StatusCode == HttpStatusCode.OK)
{
// Do stuff with response.GetResponseStream();
}
}
}
catch(Exception ex)
{
ShowError(ex);
// if the server returns a 500 error than the webRequest.GetResponse() method
// throws an exception and all I get is "The remote server returned an error: (500)."
}
Any help with this would be much appreciated.
Is this possible using HttpWebRequest and HttpWebResponse?
You could have your web server simply catch and write the exception text into the body of the response, then set status code to 500. Now the client would throw an exception when it encounters a 500 error but you could read the response stream and fetch the message of the exception.
So you could catch a WebException which is what will be thrown if a non 200 status code is returned from the server and read its body:
catch (WebException ex)
{
using (var stream = ex.Response.GetResponseStream())
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
}
catch (Exception ex)
{
// Something more serious happened
// like for example you don't have network access
// we cannot talk about a server exception here as
// the server probably was never reached
}
I came across this question when trying to check if a file existed on an FTP site or not. If the file doesn't exist there will be an error when trying to check its timestamp. But I want to make sure the error is not something else, by checking its type.
The Response property on WebException will be of type FtpWebResponse on which you can check its StatusCode property to see which FTP error you have.
Here's the code I ended up with:
public static bool FileExists(string host, string username, string password, string filename)
{
// create FTP request
FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + host + "/" + filename);
request.Credentials = new NetworkCredential(username, password);
// we want to get date stamp - to see if the file exists
request.Method = WebRequestMethods.Ftp.GetDateTimestamp;
try
{
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
var lastModified = response.LastModified;
// if we get the last modified date then the file exists
return true;
}
catch (WebException ex)
{
var ftpResponse = (FtpWebResponse)ex.Response;
// if the status code is 'file unavailable' then the file doesn't exist
// may be different depending upon FTP server software
if (ftpResponse.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
{
return false;
}
// some other error - like maybe internet is down
throw;
}
}
I faced a similar situation:
I was trying to read raw response in case of an HTTP error consuming a SOAP service, using BasicHTTPBinding.
However, when reading the response using GetResponseStream(), got the error:
Stream not readable
So, this code worked for me:
try
{
response = basicHTTPBindingClient.CallOperation(request);
}
catch (ProtocolException exception)
{
var webException = exception.InnerException as WebException;
var rawResponse = string.Empty;
var alreadyClosedStream = webException.Response.GetResponseStream() as MemoryStream;
using (var brandNewStream = new MemoryStream(alreadyClosedStream.ToArray()))
using (var reader = new StreamReader(brandNewStream))
rawResponse = reader.ReadToEnd();
}
You can also use this library which wraps HttpWebRequest and Response into simple methods that return objects based on the results. It uses some of the techniques described in these answers and has plenty of code inspired by answers from this and similar threads. It automatically catches any exceptions, seeks to abstract as much boiler plate code needed to make these web requests as possible, and automatically deserializes the response object.
An example of what your code would look like using this wrapper is as simple as
var response = httpClient.Get<SomeResponseObject>(request);
if(response.StatusCode == HttpStatusCode.OK)
{
//do something with the response
console.Writeline(response.Body.Id); //where the body param matches the object you pass in as an anonymous type.
}else {
//do something with the error
console.Writelint(string.Format("{0}: {1}", response.StatusCode.ToString(), response.ErrorMessage);
}
Full disclosure
This library is a free open source wrapper library, and I am the author of said library. I make no money off of this but have found it immensely useful over the years and am sure anyone who is still using the HttpWebRequest / HttpWebResponse classes will too.
It is not a silver bullet but supports get, post, delete with both async and non-async for get and post as well as JSON or XML requests and responses. It is being actively maintained as of 6/21/2020
Sometimes ex.Response also throws NullReferenceException so below is the best way to handle
catch (WebException ex)
{
using (var stream = ex?.Response?.GetResponseStream())
if(stream != null)
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
// todo...
}
catch (Exception ex)
{
// todo...
}
**Answer Updated on 14-03-2022**
HttpWebRequest myHttprequest = null;
HttpWebResponse myHttpresponse = null;
try
{
myHttpRequest = (HttpWebRequest)WebRequest.Create(URL);
myHttpRequest.Method = "POST";
myHttpRequest.ContentType = "application/x-www-form-urlencoded";
myHttpRequest.ContentLength = urinfo.Length;
StreamWriter writer = new StreamWriter(myHttprequest.GetRequestStream());
writer.Write(urinfo);
writer.Close();
myHttpresponse = (HttpWebResponse)myHttpRequest.GetResponse();
if (myHttpresponse.StatusCode == HttpStatusCode.OK)
{
//Success code flow
}
myHttpresponse.Close();
}
catch(WebException e) {
Console.WriteLine("This program is expected to throw WebException on successful run."+
"\n\nException Message :" + e.Message);
if(e.Status == WebExceptionStatus.ProtocolError) {
Console.WriteLine("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
Console.WriteLine("Status Description : {0}",
((HttpWebResponse)e.Response).StatusDescription);
}
**Updated Answer with try catch block**
[docs.microsoft][1]
In .NET, I am calling a rest service and getting an exception - 500 Internal Server Error.
HttpWebResponse response = request.GetResponse() as HttpWebResponse
When I analyze this in Fiddler (in TextView), I am getting many details about the proper exception that caused the error.
In my exception object, I can't get this information in the InnerException (it's null) nor in the Response object itself.
Any ideas?
Try looking at the WebException.Response Property:
catch(WebException ex)
{
Console.WriteLine(ex.Message);
if (ex.Status == WebExceptionStatus.ProtocolError)
{
Console.WriteLine("Status Code : {0}", ((HttpWebResponse)ex.Response).StatusCode);
Console.WriteLine("Status Description : {0}", ((HttpWebResponse)ex.Response).StatusDescription);
using (Stream responseStream = ex.Response.GetResponseStream())
{
if (responseStream != null)
{
using (StreamReader responseReader = new StreamReader(responseStream))
{
Console.WriteLine(responseReader.ReadToEnd());
}
}
}
}
}
The "inner" exception is happening on the remote host. The WebException has a Response property which you can read to get the details.
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);
}
}
I am initiating an HttpWebRequest and then retrieving it's response. Occasionally, I get a 500 (or at least 5##) error, but no description. I have control over both endpoints and would like the receiving end to get a little bit more information. For example, I would like to pass the exception message from server to client. Is this possible using HttpWebRequest and HttpWebResponse?
Code:
try
{
HttpWebRequest webRequest = HttpWebRequest.Create(URL) as HttpWebRequest;
webRequest.Method = WebRequestMethods.Http.Get;
webRequest.Credentials = new NetworkCredential(Username, Password);
webRequest.ContentType = "application/x-www-form-urlencoded";
using(HttpWebResponse response = webRequest.GetResponse() as HttpWebResponse)
{
if(response.StatusCode == HttpStatusCode.OK)
{
// Do stuff with response.GetResponseStream();
}
}
}
catch(Exception ex)
{
ShowError(ex);
// if the server returns a 500 error than the webRequest.GetResponse() method
// throws an exception and all I get is "The remote server returned an error: (500)."
}
Any help with this would be much appreciated.
Is this possible using HttpWebRequest and HttpWebResponse?
You could have your web server simply catch and write the exception text into the body of the response, then set status code to 500. Now the client would throw an exception when it encounters a 500 error but you could read the response stream and fetch the message of the exception.
So you could catch a WebException which is what will be thrown if a non 200 status code is returned from the server and read its body:
catch (WebException ex)
{
using (var stream = ex.Response.GetResponseStream())
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
}
catch (Exception ex)
{
// Something more serious happened
// like for example you don't have network access
// we cannot talk about a server exception here as
// the server probably was never reached
}
I came across this question when trying to check if a file existed on an FTP site or not. If the file doesn't exist there will be an error when trying to check its timestamp. But I want to make sure the error is not something else, by checking its type.
The Response property on WebException will be of type FtpWebResponse on which you can check its StatusCode property to see which FTP error you have.
Here's the code I ended up with:
public static bool FileExists(string host, string username, string password, string filename)
{
// create FTP request
FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + host + "/" + filename);
request.Credentials = new NetworkCredential(username, password);
// we want to get date stamp - to see if the file exists
request.Method = WebRequestMethods.Ftp.GetDateTimestamp;
try
{
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
var lastModified = response.LastModified;
// if we get the last modified date then the file exists
return true;
}
catch (WebException ex)
{
var ftpResponse = (FtpWebResponse)ex.Response;
// if the status code is 'file unavailable' then the file doesn't exist
// may be different depending upon FTP server software
if (ftpResponse.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
{
return false;
}
// some other error - like maybe internet is down
throw;
}
}
I faced a similar situation:
I was trying to read raw response in case of an HTTP error consuming a SOAP service, using BasicHTTPBinding.
However, when reading the response using GetResponseStream(), got the error:
Stream not readable
So, this code worked for me:
try
{
response = basicHTTPBindingClient.CallOperation(request);
}
catch (ProtocolException exception)
{
var webException = exception.InnerException as WebException;
var rawResponse = string.Empty;
var alreadyClosedStream = webException.Response.GetResponseStream() as MemoryStream;
using (var brandNewStream = new MemoryStream(alreadyClosedStream.ToArray()))
using (var reader = new StreamReader(brandNewStream))
rawResponse = reader.ReadToEnd();
}
You can also use this library which wraps HttpWebRequest and Response into simple methods that return objects based on the results. It uses some of the techniques described in these answers and has plenty of code inspired by answers from this and similar threads. It automatically catches any exceptions, seeks to abstract as much boiler plate code needed to make these web requests as possible, and automatically deserializes the response object.
An example of what your code would look like using this wrapper is as simple as
var response = httpClient.Get<SomeResponseObject>(request);
if(response.StatusCode == HttpStatusCode.OK)
{
//do something with the response
console.Writeline(response.Body.Id); //where the body param matches the object you pass in as an anonymous type.
}else {
//do something with the error
console.Writelint(string.Format("{0}: {1}", response.StatusCode.ToString(), response.ErrorMessage);
}
Full disclosure
This library is a free open source wrapper library, and I am the author of said library. I make no money off of this but have found it immensely useful over the years and am sure anyone who is still using the HttpWebRequest / HttpWebResponse classes will too.
It is not a silver bullet but supports get, post, delete with both async and non-async for get and post as well as JSON or XML requests and responses. It is being actively maintained as of 6/21/2020
Sometimes ex.Response also throws NullReferenceException so below is the best way to handle
catch (WebException ex)
{
using (var stream = ex?.Response?.GetResponseStream())
if(stream != null)
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
// todo...
}
catch (Exception ex)
{
// todo...
}
**Answer Updated on 14-03-2022**
HttpWebRequest myHttprequest = null;
HttpWebResponse myHttpresponse = null;
try
{
myHttpRequest = (HttpWebRequest)WebRequest.Create(URL);
myHttpRequest.Method = "POST";
myHttpRequest.ContentType = "application/x-www-form-urlencoded";
myHttpRequest.ContentLength = urinfo.Length;
StreamWriter writer = new StreamWriter(myHttprequest.GetRequestStream());
writer.Write(urinfo);
writer.Close();
myHttpresponse = (HttpWebResponse)myHttpRequest.GetResponse();
if (myHttpresponse.StatusCode == HttpStatusCode.OK)
{
//Success code flow
}
myHttpresponse.Close();
}
catch(WebException e) {
Console.WriteLine("This program is expected to throw WebException on successful run."+
"\n\nException Message :" + e.Message);
if(e.Status == WebExceptionStatus.ProtocolError) {
Console.WriteLine("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
Console.WriteLine("Status Description : {0}",
((HttpWebResponse)e.Response).StatusDescription);
}
**Updated Answer with try catch block**
[docs.microsoft][1]
When using the WebClient class you can check for errors and empty results by using
e.error != null
and
e.result == null
respectively. How would I handle this using the HttpWebRequest class? All examples seem to omit this yet its vital in applications.
The HttpWebRequest uses the IAsyncResult and Begin/End pairs for an operation.
You will have passed a Callback method delegate to Begin operation and then in that callback you call the End method for that operation. To catch an error that may have occured in the asynchronous part of the operation you place a try block around your call to the End method.
For example when calling BeginGetResponse you might pass this call back:-
private void Callback(IAsyncResult asyncResult)
{
try
{
HttpWebResponse resp = (HttpWebResponse)myRequest.EndGetResponse(asyncResult);
}
catch (Exception e)
{
//Something bad happened during the request
}
}
Try a REST client Framework like Spring.Rest ("Spring.Rest" on NuGet), it will do all this boilerplate code for you :
RestTemplate client = new RestTemplate("http://exemple.com/");
client.GetForObjectAsync<string>("path/", r =>
{
if (r.Error != null)
{
}
});
You can use try-catch for that.
try {
// Create a web request for an invalid site. Substitute the "invalid site" strong in the Create call with a invalid name.
HttpWebRequest myHttpWebRequest = (HttpWebRequest) WebRequest.Create("invalid site");
// Get the associated response for the above request.
HttpWebResponse myHttpWebResponse = (HttpWebResponse) myHttpWebRequest.GetResponse();
myHttpWebResponse.Close();
}
catch(WebException e) {
Console.WriteLine("This program is expected to throw WebException on successful run."+
"\n\nException Message :" + e.Message);
if(e.Status == WebExceptionStatus.ProtocolError) {
Console.WriteLine("Status Code : {0}", ((HttpWebResponse)e.Response).StatusCode);
Console.WriteLine("Status Description : {0}", ((HttpWebResponse)e.Response).StatusDescription);
}
}
catch(Exception e) {
Console.WriteLine(e.Message);
}
http://msdn.microsoft.com/en-us/library/system.net.webexception.status.aspx