In my Xamarin application I use HttpWebRequest class to send POST messages to the server (I use it because it is available out-of-the box in PCL libraries).
Here is some request preparation code:
request.BeginGetRequestStream (asyncResult => {
Mvx.Trace ("BeginGetRequestStream callback");
request = (HttpWebRequest)asyncResult.AsyncState;
Stream postStream = request.EndGetRequestStream (asyncResult);
string postData = jsonConverter.SerializeObject (objectToSend);
Mvx.Trace ("Posting following JSON: {0}", postData);
byte[] byteArray = Encoding.UTF8.GetBytes (postData);
postStream.Write (byteArray, 0, byteArray.Length);
MakeRequest (request, timeoutMilliseconds, successAction, errorAction);
}, request);
When I start application and execute this code for the first and the second time everything works fine. But when this is executed for the 3rd time (exactly!) the callback is not called and line "BeginGetRequestStream callback" is never printed to log. Is it a bug in class implementation or maybe I do something incorrectly?
If it is not possible to make this working in Xamarin please suggest reliable and convenient class for sending Http GET and POST request with timeout.
Also created related, more general question: Sending Http requests from Xamarin Portable Class Library
My solution to send and receive messages JSON in Xamarin PCL:
public async Task<string> SendMessageJSON(string message, string url)
{
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
request.ContentType = "application/json";
request.Method = "POST";
// Send data to server
IAsyncResult resultRequest = request.BeginGetRequestStream(null, null);
resultRequest.AsyncWaitHandle.WaitOne(30000); // 30 seconds for timeout
Stream streamInput = request.EndGetRequestStream(resultRequest);
byte[] byteArray = Encoding.UTF8.GetBytes(message);
await streamInput.WriteAsync(byteArray, 0, byteArray.Length);
await streamInput.FlushAsync();
// Receive data from server
IAsyncResult resultResponse = request.BeginGetResponse(null, null);
resultResponse.AsyncWaitHandle.WaitOne(30000); // 30 seconds for timeout
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(resultResponse);
Stream streamResponse = response.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string result = await streamRead.ReadToEndAsync();
await streamResponse.FlushAsync();
return result;
}
Finally solved this by switching to Profile 78 and HttpClient, which works well in all cases.
Related
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.
I want to send a HTTP PUT request to a WCF server from Windows Phone 8, and for identification I have to send a custom header. (assume "mycustomheader" = "abc")
I was using WebClient so far, but the Webclient.Headers seems not to have an Add method, so it is not possible to send headers other then the ones in HttpRequestHeader enum. Is there any way to do this with WebClient?
I saw it is possible to set a custom header with HttpWebRequest class, but I just can't get it to do anything at all. My test code (basically the sample copied from http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.begingetrequeststream.aspx):
public void dosth()
{
HttpWebRequest wr = (HttpWebRequest)WebRequest.Create("http://mycomputer/message");
wr.Method = "PUT";
wr.ContentType = "application/x-www-form-urlencoded";
wr.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), wr);
allDone.WaitOne();
}
private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
Stream postStream = request.EndGetRequestStream(asynchronousResult);
string postData = "{'Command': { 'RequestType' : 'Status', 'Test' : '1' }}";
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
postStream.Write(byteArray, 0, postData.Length);
postStream.Close();
request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
}
private static void GetResponseCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
Stream streamResponse = response.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string responseString = streamRead.ReadToEnd();
streamResponse.Close();
streamRead.Close();
response.Close();
allDone.Set();
}
As I can see with wireshark: nothing is arriving at my computer (same url and everything works fine with WebClient .. except for the custom header). In debugging I can see the GetRequestStreamCallback being fired and running through. But it never arrives in the GetResponseCallback. Most stuff I find regarding this refers to methods like GetResponse() that seem not to be available on
Whats is the way to go here? Is it possible to get the HttpWebRequest to work, or is there some workaround to get the custom header set in WebClient or is there even another better way?
edit: webclient code:
WebClient wc = new WebClient();
wc.Headers[HttpRequestHeader.ContentLength] = data.Length.ToString();
wc.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
wc.UploadStringAsync(new Uri("http://mycomputer/message"), "PUT", data);
sends the correct data to the correct url. However setting custom header seems not to be possible. (even tried \r\n inside a header ... but this is not allowed and throws exception)
Where do you set the header?
Here is how to do it:
request.Headers["mycustomheader"] = "abc";
I’m working with a WPF .net 4.0 Application. I have a search bar. For each search token I need to do 8 http request to 8 separate URLs to get search results. I send 8 requests to server after 400 milliseconds once the user stops typing in search bar. Searching for 6 to 7 search-tokens results comes very nicely. But after that suddenly HttpWebRequest stops working silently. No exception was thrown, no response was received. I'm working with Windows 7, I disabled the firewall too. I don't know where the subsequent http requests are lost.
Can anyone show me lights to fix this issue?
Below is my code for HttpWebRequest call.
public static void SendReq(string url)
{
// Create a new HttpWebRequest object.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.ContentType = "application/x-www-form-urlencoded";
request.Proxy = new WebProxy("192.168.1.1", 8000);
// Set the Method property to 'POST' to post data to the URI.
request.Method = "POST";
// start the asynchronous operation
request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
}
private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
Stream postStream = request.EndGetRequestStream(asynchronousResult);
string postData = this.PostData;
// Convert the string into a byte array.
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Write to the request stream.
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
// Start the asynchronous operation to get the response
request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
}
private static void GetResponseCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
using(HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult))
{
using(Stream streamResponse = response.GetResponseStream())
{
using(StreamReader streamRead = new StreamReader(streamResponse))
{
string responseString = streamRead.ReadToEnd();
Debug.WriteLine(responseString);
}
}
}
}
I think i am very late, but i still want to answer your question, may be it can be helpful to others. By default HTTP Request you make are HTTP 1.1 requests. And HTTP 1.1 Request by default has Keep-Alive connection. so when you make too many request to same server .net framework only make x no. of request.
you should close all your response by response.Close()
you can also specify how many simultaneous requests you can make.
ServicePointManager.DefaultConnectionLimit = 20;
Note that you have to set DefaultConnectionLimit before the first request you make. you can find more information
here on msdn.
All i can see is that in GetRequestStreamCallback you should replace
postStream.Write(byteArray, 0, postData.Length);
by
postStream.Write(byteArray, 0, byteArray.Length);
since these length aren't necessarily equal.
#Somnath
I am not sure if you found this answer, but if anyone else stumbles across this post with the same issue that Somnath and I were having.
We all try to do our due diligence in keeping memory clean and clear, but with streams we always will save unexplained issues if we make sure to flush the stream before we close it.
Replace This :
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
With This :
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Flush();
postStream.Close();
I followed all suggestion provide by all of you but couldn't stop the silent failure of HTTP request. But I found a workaround. Even myself could not reach to a final conclusion till now.
But my workaround is working well as off now without any failure.
In SendReq(string url) function i have added the following lines of code
System.Net.ServicePointManager.DefaultConnectionLimit = 100; // Just selected a random number for testing greater than 2
System.Net.ServicePointManager.SetTcpKeepAlive(true, 30, 30); // 30 is based on my server i'm hitting
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
request.KeepAlive = true;
I have create an "csv file" in my windows phone,
I want to post it, in a server, in the web and I don't find how I want to proceed for that,
I don't want just make a "post request" with parameters, I want to post my File in the server...
Actually, I'm connect to this server, but it don't find my file...
public void SentPostReport()
{
//Post response.
string url = this.CurentReportkPI.configXml.gw; // string url
Uri uri = new Uri(url);
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Accept = "application/CSV";
request.Method = "POST";
request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
}
private void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
Stream postStream = request.EndGetRequestStream(asynchronousResult);
// I create My csv File
CreateCsv reportCsv = new CreateCsv();
string pathReportFile = reportCsv.CreateNewReport(this.report);
string CsvContent = reportCsv.ReadFile(pathReportFile);
// Convert the string into a byte array.
byte[] byteArray = Encoding.UTF8.GetBytes(CsvContent);
// Write to the request stream.
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
// Start the asynchronous operation to get the response
request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
}
private static void GetResponseCallback(IAsyncResult asynchronousResult)
{
Debug.WriteLine("GetResponseCallback");
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
Stream streamResponse = response.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string responseString = streamRead.ReadLine();
// Close the stream object
streamResponse.Close();
streamRead.Close();
// Release the HttpWebResponse
response.Close();
}
Have you an idea when I proceed for resolve my problem,and send my CSV File with my request ?
Thanks.
Not sure if this is the problem here, but on a POST request, you are supposed to set the ContentLength and ContentType ("application/x-www-form-urlencoded") headers, amongst other things...
Please check this "how-to" article on a fully correct POST request -- It's not for Windows Phone, but I think you'll still get the full ideia!
On the other hand, I'd suggest you just go with RestSharp that will solve all these problems for you!
you can do this easily using RestSharp or Hammock with the AddFile method. Here's an example of what i did for uploading a photo using Hammock:
var request = new RestRequest("photo", WebMethod.Post);
request.AddParameter("photo_album_id", _album.album_id);
request.AddFile("photo", filename, e.ChosenPhoto);
request.Client.BeginRequest(request, (restRequest, restResponse, userState) =>
{
// handle response
}
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();
}
}