Welcome!
I have a little problem with own application. This app can be connect(sith socket) an FTP server, and its work fine. But my problem is, if the user use bad usernam or password, the program won't receive the response statucode. Whats wrong?
I would like to use this statuscode some clause to examine(usernem or/and password etc.)
Code:
public static void ReadResponse()
{
result = ParseHostResponse();
statusCode = int.Parse(result.Substring(0, 3));
statusMessage = "";
}
The ParseHostResponse() method contains next:
Code:
public static string ParseHostResponse()
{
SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
socketEventArg.RemoteEndPoint = socket.RemoteEndPoint;
socketEventArg.SetBuffer(buffer, BUFFER_SIZE, 0);
socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
statusMessage = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);
statusMessage = statusMessage.Trim('\0');
}
else
{
statusMessage = e.SocketError.ToString();
}
});
socket.ReceiveAsync(socketEventArg);
string[] msg = statusMessage.Split('\n');
if (statusMessage.Length > 2)
{
statusMessage = msg[msg.Length - 2];
}
else
{
statusMessage = msg[0];
}
if (!statusMessage.Substring(3, 1).Equals(" "))
{
return ParseHostResponse();
}
return statusMessage;
}
If I invite to the ReadResponse() method, the Visual Studio answer with this exception: NullReferenceException
in this code:
Code:
.
.
string[] msg = statusMessage.Split('\n');
.
What is the wrong? This code issue to http://msdn.microsoft.com/en-us/library/hh202858%28v=vs.92%29.aspx#BKMK_RECEIVING
Thank you for your help!
I can't help, but have to start with these side remarks:
statusMessage.Trim('\0') does not work (try it)
statusMessage.Split('\n') is inefficient as it involves extra allocations (guess why)
Now to the actual subject: I never used sockets on WP7, but from what I know about async operations it looks to me that you start async op (by calling ReceiveAsync) and use the result (statusMessage) before the answer arrives.
Think a bit about your design of the ParseHostResponse() method:
Bad name: Indicates parsing of a response, while it actually performs communication
Bad functionality: The method indicates sync patter, but internally uses async pattern. I don't know what to suggest here as every solution seems to be wrong. For example waiting for a response will make UI irresposible.
My main recommendation is that you get more information about async programming and then reprogramm your app accordingly.
Related
I am struggling with uploading an image from thew client-side to a folder on the server-side in .Net Core.I used Postman to check if the method on the server-side is working and it does without any problem,but when I try to upload an image from the client-side,I get an error on the server-side of type NullReferenceException:Object reference not set to an instance of an object.This is the Post method on the server-side:
[HttpPost]
public async Task Post(IFormFile file)
{
if (string.IsNullOrWhiteSpace(_environment.WebRootPath))
{
_environment.WebRootPath = Path.Combine(Directory.GetCurrentDirectory(), "wwwroot");
}
var uploads = Path.Combine(_environment.WebRootPath, "uploads");
//var fileName = file.FileName.Split('\\').LastOrDefault().Split('/').LastOrDefault();
if (!Directory.Exists(uploads)) Directory.CreateDirectory(uploads);
if (file.Length > 0)
{
using (var fileStream = new FileStream(Path.Combine(uploads, file.FileName), FileMode.Create))
{
await file.CopyToAsync(fileStream);
}
}
}
Apparently the method is thrown where I check if the length of the file is bigger than 0.On the client-side I get error "500 internal server error" and I tried to check using the debugger where exactly the error is thrown but i can't find anything that could resemble an error of some sort.This is the API method for the client-side:
public async Task UploadPictureAsync(MediaFile image)
{
User user = new User();
string pictureUrl = "http://10.0.2.2:5000/api/UploadPicture";
HttpContent fileStreamContent = new StreamContent(image.GetStream());
// user.Picture=GetImageStreamAsBytes(image.GetStream());
fileStreamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data") {FileName=Guid.NewGuid() + ".Png",Name="image"};
fileStreamContent.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
HttpClientHandler clientHandler = new HttpClientHandler();
clientHandler.ServerCertificateCustomValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; };
using (var client = new HttpClient(clientHandler))
{
using (var formData = new MultipartFormDataContent())
{
formData.Add(fileStreamContent);
var response = await client.PostAsync(pictureUrl, formData);
if(response.IsSuccessStatusCode)
{
var result = response.Content.ReadAsStringAsync().Result;
}
}
}
}
The image is declared in the Model as byte array:
public byte[] Picture { get; set; }
Does someone understand why my POST method has this behavior since the server-side works perfectly but fails when I try to upload an image from the client-side?What I find weird though is that when i read the error and I look at the Content-Type it is "text/plain" instead of "form-data" and I have tried to set it at the MutipartFormDataContent like this:
formData.Headers.ContentType.MediaType = "multipart/form-data";
I also tried to set the MediaTypeHeaderValue on the client like this:
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/octet-stream"));
I still get the wrong content type.
I have also tried a different approach with Stream instead of MediaFile but without any luck as it did not even hit the break point in debugger mode for the response.Any help would be appreciated! :)
I have managed to find the answer finalllyyyyy!!!The problem was on the client-side as I suspected and guess what,it was all about the correct name.It turns out that since on the server side I have IFormFile file I had to change the client side to take the parameter name "file" instead of image as well so that it could work.Thank you #Jason for the suggestions as I didn't understand the error from the first place and did some debugging on the server-side to help me figure it out.
We are using xamarin forms. After an Android or IOS device resumes from background, we are making a REST call in .net that is being triggered by a timer. The first attempt on IOS returns a "The Descriptor is not a socket" error and the Android returns a "Connection refused" error. The same code works fine in Windows. Future attempts (every few seconds) in all 3 platforms work fine. Has anyone seen this and have a fix?
Code
//app on resume event
protected async override void OnResume()
{
// Handle when your app resumes
if (MainPage is RootPage)
{
RootPage mainPage = MainPage as RootPage;
if (mainPage.Detail is NavigationPage)
{
NavigationPage nvPage = mainPage.Detail as NavigationPage;
if(nvPage.CurrentPage is ThingsPage)
{
ThingsPage thPage = nvPage.CurrentPage as ThingsPage;
thPage.TurnOnTimer();
}
}
}
}
//code on the page
public void TurnOnTimer()
{
if (viewModel != null)
{
viewModel.ContinueTimer = true;
viewModel.StartAnotherTimer();
}
}
//code in view model
public async void StartAnotherTimer()
{
while (ContinueTimer)
{
try
{
DevicesUpdate devicesUpdate = await DataSource.GetDevices(LocationID, ControllerID, lastDevicesUpdateReceivedAt);
}
catch (Exception ex)
{
}
// Update the UI (because of async/await magic, this is still in the UI thread!)
if (ContinueTimer)
{
await Task.Delay(TimeSpan.FromSeconds(3));
}
}
}
public static async Task<DevicesUpdate> GetDevices(Guid locationID, Guid controllerID, DateTime lastUpdateReceivedAt)
{
DevicesUpdate devicesUpdate = await GetLastUpdatedDevices(controllerID, lastUpdateReceivedAt);
}
//code in view model
public static async Task<DevicesUpdate> GetLastUpdatedDevices(Guid controllerID,
DateTime lastUpdate)
{
System.Net.Http.HttpClient client = new System.Net.Http.HttpClient();
string url = string.Format("http://appname.azurewebsites.net/api/devices?controllerid={1}&lastUpdate={2}"
, Constants.WebServerURL, controllerID, lastUpdate);
System.Net.Http.HttpResponseMessage response = await client.GetAsync(new Uri(url));
string result = await response.Content.ReadAsStringAsync();
if (response.IsSuccessStatusCode)
{
DevicesUpdate devices = JSONHelper.Deserialize<DevicesUpdate>(result);
return devices;
}
else
{
if (response.ReasonPhrase == "UserException")
{
throw new UserException(result);
}
else
{
//throw error because the response from rest api is not a success
throw new System.Net.Http.HttpRequestException(result);
}
}
}
You might have a few things happening here that's causing problems.
GetDevices doesn't return anything. (I hope you just left out the return for brevity sake)
You are never setting ContinueTimer to false.
What iOS version are you on? In later versions, you HAVE to use HTTPS or explicitly allow non-secure connections. This shouldn't be a problem because Azure has ssl.
If you plan on running this in the background, you need to register your app as a background process.
If you don't plan on running this in the background, you might have issues with previous attempts being ran (or still trying to execute, or just have failed) and then calling more.
What is the reason for calling the 3 second timer for the network calls? What if the call takes more than 3 seconds (then you are making duplicate calls even though the first might succeed).
If you want to make your network calls more robust, check out this Blog Post by Rob Gibbons about resilient network calls.
First thing I would do is remove it from the timer because it seems like the underlying sockets are having issues cross-thread.
Would using Thread.CurrentPrincipal's claims in a referenced library that uses ConfigureAwait(false) pose any problems or will the flowing of ExecutionContext's logical call context take care of me there? (my reading and testing so far indicates that it will).
Example WebAPI Controller Action:
[CustomAuthorizeThatSetsCurrentUsersClaimsToThreadCurrentContextAndHttpContextCurrentUser]
public async Task<Order> Get(int orderId)
{
return await _orderBusinessLogicLibrary.LoadAsync(orderId); // defaults to .ConfigureAwait(true)
}
Example load functions from external, referenced library:
[ClaimsPrincipalPermission(
SecurityAction.Demand,
Operation="Read",
Resource="Orders")]
[ClaimsPrincipalPermission(
SecurityAction.Demand,
Operation="Read",
Resource="OrderItems")]
public async Task<Order> Load(int orderId)
{
var order = await _repository.LoadOrderAsync(orderId).ConfigureAwait(false);
// here's the key line.. assuming this lower-level function is also imposing
// security constraints in the same way this method does, would
// Thread.CurrentPrincipal still be correct inside the function below?
order.Items = await _repository.LoadOrderItemsAsync(orderId).ConfigureAwait(false);
return order;
}
Also, the answer can't be "well don't use ConfigureAwait(false) then!". That can cause other problems such as deadlock (Don't Block on Async Code).
From my tests, it appears that Thread.CurrentPrincipal will flow correctly, even if you use ConfigureAwait(false). The following WebAPI code sets the principal and then blocks on an async call, forcing another thread to resume the async method. That other thread does inherit the correct principal.
private async Task<string> Async()
{
await Task.Delay(1000).ConfigureAwait(false);
return "Thread " + Thread.CurrentThread.ManagedThreadId + ": " + Thread.CurrentPrincipal.Identity.Name + "\n";
}
public string Get(int id)
{
var user = new ClaimsPrincipal(new ClaimsIdentity(
new[]
{
new Claim(ClaimTypes.Name, "Bob"),
}
));
HttpContext.Current.User = user;
Thread.CurrentPrincipal = user;
var ret = "Thread " + Thread.CurrentThread.ManagedThreadId + ": " + Thread.CurrentPrincipal.Identity.Name + "\n";
ret += Async().Result;
return ret;
}
When I run this code on a new instance of IISExpress, I get:
"Thread 7: Bob\nThread 6: Bob\n"
However, I should point out that using ConfigureAwait(false) to avoid deadlock is not recommended. This is especially true on ASP.NET. If at all possible, use ConfigureAwait(false) and also use async all the way. Note that WebAPI is a fully-async stack and you should be able to do this.
Reccently, I am working on a project in Windows Phone. and In this project, to validate a user, I need to check at 3 web API, the logic is like below:
Step 1: access web api 1 to get the token
Step 2: access web api 2 to get the username/password by the token retrieved in Step 1
Step 3: access web API 3 to validate the user name/password in step 2
you can see we need to access those 3 API in order. as well know, window phone now access the network asynchronously, which causes a big challenge on make those API access in order, and which make the soure code hard to maintainace.
I also consider the synchronous source code like below, but I found there are some problems to access the network,many exeption will be thrown. For example, when an exception is thrown, I try to use asynchronous web request to access the same URL, it is OK. I am strugglig in it now. And I have to introduce thread to call it to avoid to block the UI thread.
internal static class HttpWebRequestExtensions
{
public const int DefaultRequestTimeout = 60000;
public static bool IsHttpExceptionFound = false;
public static WebResponse GetResponse(this WebRequest request, int nTimeOut = DefaultRequestTimeout)
{
var dataReady = new AutoResetEvent(false);
HttpWebResponse response = null;
var callback = new AsyncCallback(delegate(IAsyncResult asynchronousResult)
{
try
{
response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
dataReady.Set();
}
catch(Exception e)
{
IsHttpExceptionFound = true;
}
});
request.BeginGetResponse(callback, request);
if (dataReady.WaitOne(nTimeOut))
{
return response;
}
return null;
}
public static WebResponse PostRequest(this HttpWebRequest request, String postData, int nTimeOut = DefaultRequestTimeout)
{
var dataReady = new AutoResetEvent(false);
HttpWebResponse response = null;
var callback = new AsyncCallback(delegate(IAsyncResult asynchronousResult)
{
Stream postStream = request.EndGetRequestStream(asynchronousResult); //End the operation.
byte[] byteArray = Encoding.UTF8.GetBytes(postData); //Convert the string into a byte array.
postStream.Write(byteArray, 0, postData.Length); //Write to the request stream.
postStream.Close();
dataReady.Set();
});
request.BeginGetRequestStream(callback, request);
if (dataReady.WaitOne(nTimeOut))
{
response = (HttpWebResponse)request.GetResponse(nTimeOut);
if (IsHttpExceptionFound)
{
throw new HttpResponseException("Failed to get http response");
}
return response;
}
return null;
}
}
Any suggestion on using asynchronous web request to solve my case?
There's an example here of using asynchronous web services in a chained manner to call the Microsoft Translator service on WP7
Maybe it will give you some pointers?
http://blogs.msdn.com/b/translation/p/wp7translate.aspx
I have a Action that sends a simple email:
[HttpPost, ActionName("Index")]
public ActionResult IndexPost(ContactForm contactForm)
{
if (ModelState.IsValid)
{
new EmailService().SendAsync(contactForm.Email, contactForm.Name, contactForm.Subject, contactForm.Body, true);
return RedirectToAction(MVC.Contact.Success());
}
return View(contactForm);
}
And a email service:
public void SendAsync(string fromEmail, string fromName, string subject, string body, bool isBodyHtml)
{
MailMessage mailMessage....
....
SmtpClient client = new SmtpClient(settingRepository.SmtpAddress, settingRepository.SmtpPort);
client.EnableSsl = settingRepository.SmtpSsl;
client.Credentials = new NetworkCredential(settingRepository.SmtpUserName, settingRepository.SmtpPassword);
client.SendCompleted += client_SendCompleted;
client.SendAsync(mailMessage, Tuple.Create(client, mailMessage));
}
private void client_SendCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
{
Tuple<SmtpClient, MailMessage> data = (Tuple<SmtpClient, MailMessage>)e.UserState;
data.Item1.Dispose();
data.Item2.Dispose();
if (e.Error != null)
{
}
}
When I send a email, I am using Async method, then my method SendAsync return immediately, then RedirectToAction is called. But the response(in this case a redirect) isn´t sent by ASP.NET until client_SendCompleted is completed.
Here's what I'm trying to understand:
When watching the execution in Visual Studio debugger, the SendAsync returns immediately (and RedirectToAction is called), but nothing happens in the browser until email is sent?
If i put a breakpoint inside client_SendCompleted, the client stay at loading.... until I hit F5 at debugger.
This is by design. ASP.NET will automatically wait for any outstanding async work to finish before finishing the request if the async work was kicked off in a way that calls into the underlying SynchronizationContext. This is to ensure that if your async operation tries to interact with the HttpContext, HttpResponse, etc. it will still be around.
If you want to do true fire & forget, you need to wrap your call in ThreadPool.QueueUserWorkItem. This will force it to run on a new thread pool thread without going through the SynchronizationContext, so the request will then happily return.
Note however, that if for any reason the app domain were to go down while your send was still in progress (e.g. if you changed the web.config file, dropped a new file into bin, the app pool recycled, etc.) your async send would be abruptly interrupted. If you care about that, take a look at Phil Haacks WebBackgrounder for ASP.NET, which let's you queue and run background work (like sending an email) in such a way that will ensure it gracefully finishes in the case the app domain shuts down.
This is an interesting one. I've reproduced the unexpected behaviour, but I can't explain it. I'll keep digging.
Anyway the solution seems to be to queue a background thread, which kind of defeats the purpose in using SendAsync. You end up with this:
MailMessage mailMessage = new MailMessage(...);
SmtpClient client = new SmtpClient(...);
client.SendCompleted += (s, e) =>
{
client.Dispose();
mailMessage.Dispose();
};
ThreadPool.QueueUserWorkItem(o =>
client.SendAsync(mailMessage, Tuple.Create(client, mailMessage)));
Which may as well become:
ThreadPool.QueueUserWorkItem(o => {
using (SmtpClient client = new SmtpClient(...))
{
using (MailMessage mailMessage = new MailMessage(...))
{
client.Send(mailMessage, Tuple.Create(client, mailMessage));
}
}
});
With .Net 4.5.2, you can do this with ActionMailer.Net:
var mailer = new MailController();
var msg = mailer.SomeMailAction(recipient);
var tcs = new TaskCompletionSource<MailMessage>();
mailer.OnMailSentCallback = tcs.SetResult;
HostingEnvironment.QueueBackgroundWorkItem(async ct =>
{
msg.DeliverAsync();
await tcs.Task;
Trace.TraceInformation("Mail sent to " + recipient);
});
Please read this first: http://www.hanselman.com/blog/HowToRunBackgroundTasksInASPNET.aspx
I sent the bug to Microsoft Connect https://connect.microsoft.com/VisualStudio/feedback/details/688210/smtpclient-sendasync-blocking-my-asp-net-mvc-request