Any ideas why on some links that I try to access using HttpWebRequest I am getting "The remote server returned an error: (304) Not Modified." in the code?
The code I'm using is from Jeff's post here (the page seems to have disappeared, see an archive copy at the Wayback Machine).
Note the concept of the code is a simple proxy server, so I'm pointing my browser at this locally running piece of code, which gets my browsers request, and then proxies it on by creating a new HttpWebRequest, as you'll see in the code. It works great for most sites/links, but for some this error comes up. You will see one key bit in the code is where it seems to copy the http header settings from the browser request to it's request out to the site, and it copies in the header attributes. Not sure if the issue is something to do with how it mimics this aspect of the request and then what happens as the result comes back?
case "If-Modified-Since":
request.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]);
break;
I get the issue for example from http://en.wikipedia.org/wiki/Main_Page
PS. UPDATE HERE
Still can't work this out. Basically I can identify 1 link which has an issue, and it seems to work fine, 2nd time it gets the error, 3rd time OK, 4th time gets the error, 5th time OK etc. As if there is some state not getting cleared or something in the code. I've tried to clean up the code a bit using "using" type statements etc.
Here's the code. If anyone can spot why every 2nd time I browse to a link like http://newsimg.bbc.co.uk/css/screen/1_0_16/nol/v4/story.css (starting at the 2nd time, not the first) via this proxy code I get the error I'd love to hear.
class Program
{
static void Main(string[] args)
{
Proxy p = new Proxy(8080);
Thread proxythread = new Thread(new ThreadStart(p.Start));
proxythread.Start();
Console.WriteLine("Proxy Started. Press Any Key To Stop...");
Console.ReadKey();
p.Stop();
}
}
public class Proxy
{
private HttpListener _listener;
private int _port;
public Proxy(int port)
{
int defaultport = 8080;
// Setup Thread Pool
System.Threading.ThreadPool.SetMaxThreads(50, 1000);
System.Threading.ThreadPool.SetMinThreads(50, 50);
// Sanitize Port Number
if (port < 1024 || port > 65535)
port = defaultport;
// Create HttpListener Prefix
string prefix = string.Format("http://*:{0}/", port);
_port = port;
// Create HttpListener
_listener = new HttpListener();
_listener.Prefixes.Add(prefix);
}
public void Start()
{
_listener.Start();
while (true)
{
HttpListenerContext request = null;
try
{
request = _listener.GetContext();
// Statistics (by Greg)
int availThreads = -1;
int compPortThreads = -1;
ThreadPool.GetAvailableThreads(out availThreads, out compPortThreads);
log("INFO", request.Request.Url.ToString(), "START - [" + availThreads + "]");
ThreadPool.QueueUserWorkItem(ProcessRequest, request);
}
catch (HttpListenerException ex)
{
log("ERROR", "NA", "INFO: HttpListenerException - " + ex.Message);
break;
}
catch (InvalidOperationException ex)
{
log("ERROR", "NA", "INFO: InvalidOperationException - " + ex.Message);
break;
}
}
}
public void Stop()
{
_listener.Stop();
}
private void log(string sev, string uri, string message)
{
Console.Out.WriteLine(Process.GetCurrentProcess().Id + " - " + sev + " (" + uri + "): " + message);
}
private void ProcessRequest(object _listenerContext)
{
#region local variables
HttpWebRequest psRequest; // Request to send to remote web server
HttpWebResponse psResponse; // Response from remote web server
List<byte> requestBody = new List<byte>(); // Byte array to hold the request's body
List<byte> responseBody = new List<byte>(); // Byte array to hold the response's body
byte[] buffer;
string uri = "";
#endregion
var listenerContext = (HttpListenerContext)_listenerContext;
uri = listenerContext.Request.Url.ToString().Replace(string.Format(":{0}", _port), "");
// Create Interent Request
HttpWebRequest internetRequest = (HttpWebRequest)WebRequest.Create(uri);
#region Build Request Up
internetRequest.Method = listenerContext.Request.HttpMethod;
internetRequest.ProtocolVersion = listenerContext.Request.ProtocolVersion;
internetRequest.UserAgent = listenerContext.Request.UserAgent;
foreach (string key in listenerContext.Request.Headers.AllKeys)
{
try
{
switch (key)
{
case "Proxy-Connection":
case "Connection":
internetRequest.KeepAlive = (listenerContext.Request.Headers[key].ToLower() == "keep-alive") ? true : false;
break;
case "Content-Length":
internetRequest.ContentLength = listenerContext.Request.ContentLength64;
break;
case "Content-Type":
internetRequest.ContentType = listenerContext.Request.ContentType;
break;
case "Accept":
internetRequest.Accept = listenerContext.Request.Headers[key];
break;
case "Host":
break;
case "Referer":
internetRequest.Referer = listenerContext.Request.Headers[key];
break;
case "If-Modified-Since":
internetRequest.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]);
break;
default:
internetRequest.Headers.Add(key, listenerContext.Request.Headers[key]);
break;
}
}
catch (Exception ex)
{
Console.WriteLine("Error settup up psRequest object. Error = " + ex.Message + "\n" + ex.StackTrace);
}
}
#endregion
#region Copy content into request
buffer = new byte[1024];
using (Stream instream = listenerContext.Request.InputStream)
{
int incount = instream.Read(buffer, 0, buffer.Length);
while (incount > 0)
{
internetRequest.GetRequestStream().Write(buffer, 0, incount);
incount = instream.Read(buffer, 0, buffer.Length);
}
}
#endregion
// Get Internet Response
HttpWebResponse internetResponse = null;
try
{
using (internetResponse = (HttpWebResponse)internetRequest.GetResponse())
{
#region Configure Local Response Header Keys
foreach (string key in internetResponse.Headers.Keys)
{
try
{
switch (key)
{
case "Transfer-Encoding":
listenerContext.Response.SendChunked = (internetResponse.Headers[key].ToLower() == "chunked") ? true : false;
break;
case "Content-Length":
listenerContext.Response.ContentLength64 = internetResponse.ContentLength;
break;
case "Content-Type":
listenerContext.Response.ContentType = internetResponse.Headers[key];
break;
case "Keep-Alive":
listenerContext.Response.KeepAlive = true;
break;
default:
listenerContext.Response.Headers.Add(key, internetResponse.Headers[key]);
break;
}
}
catch (Exception ex)
{
log("ERROR", uri, "Error settup up listenerContext.Response objects. Error = " + ex.Message + "\n" + ex.StackTrace);
}
}
#endregion
try
{
// Transfer the body data from Internet Response to Internal Response
buffer = new byte[1024];
using (Stream inputStream = internetResponse.GetResponseStream())
{
int outcount = inputStream.Read(buffer, 0, buffer.Length);
while (outcount > 0)
{
listenerContext.Response.OutputStream.Write(buffer, 0, outcount);
outcount = inputStream.Read(buffer, 0, buffer.Length);
}
}
}
catch (Exception ex)
{
log("ERROR", uri, "Could not obtain response from URI: " + ex.Message);
}
finally
{
listenerContext.Response.OutputStream.Close();
}
}
}
catch (Exception ex)
{
//if (ex is InvalidOperationException ||
// ex is ProtocolViolationException ||
// ex is WebException)
//{
// log(uri, "Could not successfully get response: " + ex.GetType() + " - " + ex.Message);
// listenerContext.Response.Close();
// return;
//}
//else { throw; }
log("ERROR", uri, "Could not successfully get response: " + ex.GetType() + " - " + ex.Message);
listenerContext.Response.Close();
}
}
}
And here is an example of what I see - first hit is good, 2nd has error...
Proxy Started. Press Any Key To Stop...
2080 - INFO (http://newsimg.bbc.co.uk:8080/css/screen/1_0_16/nol/v4/story.css): START - [50]
2080 - INFO (http://newsimg.bbc.co.uk:8080/css/screen/1_0_16/nol/v4/story.css): START - [50]
2080 - ERROR (http://newsimg.bbc.co.uk/css/screen/1_0_16/nol/v4/story.css): Could not successfully get response: System.Net.WebException - The remote server returned an error: (304) Not Modified.
First, this is not an error. The 3xx denotes a redirection. The real errors are 4xx (client error) and 5xx (server error).
If a client gets a 304 Not Modified, then it's the client's responsibility to display the resouce in question from its own cache. In general, the proxy shouldn't worry about this. It's just the messenger.
This is intended behavior.
When you make an HTTP request, the server normally returns code 200 OK. If you set If-Modified-Since, the server may return 304 Not modified (and the response will not have the content). This is supposed to be your cue that the page has not been modified.
The authors of the class have foolishly decided that 304 should be treated as an error and throw an exception. Now you have to clean up after them by catching the exception every time you try to use If-Modified-Since.
Just pressing F5 is not always working.
why?
Because your ISP is also caching web data for you.
Solution: Force Refresh.
Force refresh your browser by pressing CTRL + F5 in Firefox or Chrome to clear ISP cache too, instead of just pressing F5
You then can see 200 response instead of 304 in the browser F12 developer tools network tab.
Another trick is to add question mark ? at the end of the URL string of the requested page:
http://localhost:52199/Customers/Create?
The question mark will ensure that the browser refresh the request without caching any previous requests.
Additionally in Visual Studio you can set the default browser to Chrome in Incognito mode to avoid cache issues while developing, by adding Chrome in Incognito mode as default browser, see the steps (self illustrated):
It is not an issue it is because of caching...
To overcome this add a timestamp to your endpoint call, e.g. axios.get('/api/products').
After timestamp it should be axios.get(/api/products?${Date.now()}.
It will resolve your 304 status code.
I think you have not installed these features. see below in picture.
I also suffered from this problem some days ago. After installing this feature then I solved it. If you have not installed this feature then installed it.
Install Process:
go to android studio
Tools
Android
SDK Manager
Appearance & Behavior
Android SDK
Related
So I have to API's running on Kubernetes. One has a controller function as such:
string filePath = "/blobs/data/runsession/" + folderName;
if (!Directory.Exists(filePath))
return null;
var tempFile = Path.Combine(Path.GetTempPath(), guid.ToString());
logger.Info("GetTempPath()" + Path.GetTempPath());
logger.Info("Temp path is: " + tempFile);
ZipFile.CreateFromDirectory(filePath, (tempFile + ".zip"));
byte[] fileBytes = File.ReadAllBytes(tempFile + ".zip");
HelpMethods.GetNetworkTimeStamp("Stop", 2);
return fileBytes;
This controller method works fine and when I call it from postman it returns a file.
Now in the other API I want to call this function from one of my service classes as such:
public async Task<byte[]> DownloadRunSession(string foldername)
{
try
{
var request = new RestRequest($"blob/{foldername}")
{
Timeout = -1,
};
var response = await client.ExecuteGetAsync(request);
if (!response.IsSuccessful)
{
Console.WriteLine("File download failed");
Console.WriteLine(response.Content.ToString());
return null;
}
return response.RawBytes;
}catch(Exception e)
{
Console.WriteLine(e.Message);
Console.WriteLine(e.StackTrace);
return null;
}
Now the server logs on the API that sends the file Give me a status 200 but says "the application aborted the connection", and the API that is supposed to receive the file gets no response and the response variable is always "null".
Any one that has had a similar dilemma and knows how to solve it?
I have strange problem with my Game written in Unity (Mono). I have login functionality and then, after successfull login i'm sending some kind of keep-alive requests to ensure token is updated (I'm sending it every 30s).
The problem is, that after some time (sometimes it's 1 hour, sometimes 2.5 hours) all my requests have timeout status.
To be sure about my connection status I made some checks in code: I'm making simple GET to http://google.com and to main website of my API (not an API call. Just website GET). When I got timeout on API next time i figured out that:
After 1 timeout I have it always. Restarting application helps
I'm getting timeouts on API call and on GET request for base API website
Google is still responding with status 200 (no timeouts here)
Implementation:
On beginning i've been using RestSharp to handle requests, but the problem occured and there was a decision to throw RestSharp away and now we're using classic WebClient
class BetterWebClient : WebClient
{
private WebRequest _Request = null;
public TimeSpan? Timeout { get; set; }
protected override WebRequest GetWebRequest(Uri address)
{
this._Request = base.GetWebRequest(address);
if ( Timeout.HasValue )
{
_Request.Timeout = (int)Timeout.Value.TotalMilliseconds;
}
else
{
_Request.Timeout = 10*1000; //10s
}
if (this._Request is HttpWebRequest)
{
((HttpWebRequest)this._Request).AllowAutoRedirect = true;
}
return this._Request;
}
}
My HandleRequest function (which also calls Google and API website) looks like this:
public static void HandleRequest<TR>(string url, RestResponse<TR> executeGetRequest) where TR : new()
{
using (BetterWebClient w = new BetterWebClient() {Timeout = TimeSpan.FromSeconds(2)})
{
try
{
string downloadString = w.DownloadString("http://www.google.com");
Debug.Log("Google request: OK");
}
catch ( Exception )
{
Debug.LogError("Google request failed");
}
try
{
string downloadString = w.DownloadString("myAPIwebsite");
Debug.Log("WorldOfRescue.com request: OK");
}
catch ( Exception )
{
Debug.LogError("WorldOfRescue.com request failed");
}
}
var client = new BetterWebClient() {Timeout = TimeSpan.FromSeconds(5)};
client.Headers.Add("Accept", "application/json");
client.Headers.Add("Content-Type", "application/json");
try
{
string downloadString = client.DownloadString(url);
Debug.Log("Request for "+url+ " completed. Response: " + downloadString);
}
catch ( WebException e )
{
Debug.Log(e.Status);
throw;
}
catch ( Exception e )
{
Debug.Log(e.ToString());
throw;
}
finally
{
client.Dispose();
}
}
Do you have any idea why it happens? It looks like something is blocking me to send request to specific website, but in same time other website is working fine.
REQUEST :
URL: http://localhost:8080/RESTfulExample/rest/file/upload
METHOD : POST
HEADER: Content-Type : multipart/form-data
RESPONSE :
HTTP Status 400 - Bad Request
The same code is working with html forms but in postman it's throwing 400 BAD REQUEST, I looked up on google for solution and found that boundary is missing, How to resolve it ? As I have to recieve files from multiple clients like mobile application and web clients via Jquery and rest client.
#Path("/file")
public class UploadFileService {
#POST
#Path("/upload")
#Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadFile(#FormDataParam("file") InputStream uploadedInputStream,
#FormDataParam("file") FormDataContentDisposition fileDetail) {
try {
String uploadedFileLocation = "/home/nash/" + fileDetail.getFileName();
// save it
writeToFile(uploadedInputStream, uploadedFileLocation);
String output = "File uploaded to : " + uploadedFileLocation;
System.out.println("File uploaded..........");
return Response.status(200).entity(output).build();
} catch (Exception e) {
e.printStackTrace();
System.out.println("Exception " + e);
return null;
}
}
// save uploaded file to new location
private void writeToFile(InputStream uploadedInputStream, String uploadedFileLocation) {
try {
OutputStream out = new FileOutputStream(new File(uploadedFileLocation));
int read = 0;
byte[] bytes = new byte[1024];
out = new FileOutputStream(new File(uploadedFileLocation));
while ((read = uploadedInputStream.read(bytes)) != -1) {
out.write(bytes, 0, read);
}
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Please follow these steps:
Add jersey-multipart dependency.
In Your Application Class (or in web.xml) enable MultipartFeature.class.
DO NOT Add Content-Type header in your postman request.
For me the above steps worked. Do let me know if that helped you or not.
I am calling a web service from BlackBerry using J2ME code. When I try to open a connection using HttpConnection, it is checking only the GPRS connection. Now, I want to check the Wi-Fi connection and call a webservice through Wi-Fi.
The following code is my connection section. How to change the code for a Wi-Fi connection?
public boolean HttpUrl()
{
HttpConnection conn = null;
OutputStream out = null;
String url = "http://www.google.com";
try
{
conn = (HttpConnection) new ConnectionFactory().getConnection(url).getConnection();
if (conn != null)
{
conn.setRequestMethod(HttpConnection.POST);
conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("User-Agent", "Profile/MIDP-2.0 Configuration/CLDC-1.0");
}
}
catch (Exception e)
{
return false;
}
finally
{
try
{
out.close();
}
catch (Exception e2)
{
}
}
//Only if exception occurs, we close the connection.
//Otherwise the caller should close the connection himself.
try
{
conn.close();
}
catch (Exception e1)
{
}
return true;
}
Check this way:
HttpConnection conn = null;
String URL = "http://www.myServer.com/myContent;deviceside=true;interface=wifi";
conn = (HttpConnection)Connector.open(URL);
source
Making Connections
Rafael's answer will certainly work if you know you'll only be using Wi-Fi.
However, if you only need to support BlackBerry OS 5.0 - 7.1, I would recommend that you do use the ConnectionFactory. Normally, you will not limit your code to only using one transport. You'll normally support (almost) any transport the device has, but you may want to code your app to choose certain transports first.
For example,
class ConnectionThread extends Thread
{
public void run()
{
ConnectionFactory connFact = new ConnectionFactory();
connFact.setPreferredTransportTypes(new int[] {
TransportInfo.TRANSPORT_TCP_WIFI,
TransportInfo.TRANSPORT_BIS_B,
TransportInfo.TRANSPORT_MDS,
TransportInfo.TRANSPORT_TCP_CELLULAR
});
ConnectionDescriptor connDesc;
connDesc = connFact.getConnection("http://www.google.com");
if (connDesc != null)
{
HttpConnection httpConn;
httpConn = (HttpConnection)connDesc.getConnection();
try
{
// TODO: set httpConn request method and properties here!
final int iResponseCode = httpConn.getResponseCode();
UiApplication.getUiApplication().invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("Response code: " +
Integer.toString(iResponseCode));
}
});
}
catch (IOException e)
{
System.err.println("Caught IOException: "
+ e.getMessage());
}
}
}
}
will choose the Wi-Fi transport if Wi-Fi is available, but use the GPRS connection if it isn't. I think this is generally considered best practice for the 5.0+ devices.
Request Properties
This code
conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");
is not right. Content-Length should be the size, in bytes, of your HTTP POST parameters. See an example here.
Threading
Remember that making network connections is slow. Do not block the user interface by running this code on the main/UI thread. Put your code into a background thread to keep the UI responsive while you request remote content.
I'm using Web API to stream large files to clients, but I'd like to log if the download was successful or not. That is, if the server sent the entire content of the file.
Is there some way to get a a callback or event when the HttpResponseMessage completes sending data?
Perhaps something like this:
var stream = GetMyStream();
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContent(stream);
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
// This doesn't exist, but it illustrates what I'm trying to do.
response.OnComplete(context =>
{
if (context.Success)
Log.Info("File downloaded successfully.");
else
Log.Warn("File download was terminated by client.");
});
EDIT: I've now tested this using a real connection (via fiddler).
I inherited StreamContent and added my own OnComplete action which checks for an exception:
public class StreamContentWithCompletion : StreamContent
{
public StreamContentWithCompletion(Stream stream) : base (stream) { }
public StreamContentWithCompletion(Stream stream, Action<Exception> onComplete) : base(stream)
{
this.OnComplete = onComplete;
}
public Action<Exception> OnComplete { get; set; }
protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
{
var t = base.SerializeToStreamAsync(stream, context);
t.ContinueWith(x =>
{
if (this.OnComplete != null)
{
// The task will be in a faulted state if something went wrong.
// I observed the following exception when I aborted the fiddler session:
// 'System.Web.HttpException (0x800704CD): The remote host closed the connection.'
if (x.IsFaulted)
this.OnComplete(x.Exception.GetBaseException());
else
this.OnComplete(null);
}
}, TaskContinuationOptions.ExecuteSynchronously);
return t;
}
}
Then I use it like so:
var stream = GetMyStream();
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContentWithCompletion(stream, ex =>
{
if (ex == null)
Log.Info("File downloaded successfully.");
else
Log.Warn("File download was terminated by client.");
});
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
return response;
I am not sure if there is direct signaling that all is ok, but you can use a trick to find out that the connection is exist just before you end it up, and right after you fully send the file.
For example the Response.IsClientConnected is return true if the client is still connected, so you can check something like:
// send the file, make a flush
Response.Flush();
// and now the file is fully sended check if the client is still connected
if(Response.IsClientConnected)
{
// log that all looks ok until the last byte.
}
else
{
// the client is not connected, so maybe have lost some data
}
// and now close the connection.
Response.End();
if the server sent the entire content of the file
Actually there is nothing to do :)
This might sound very simplistic but you will know if an exception is raised - if you care about server delivering and not client cancelling halfway. IsClientConnected is based on ASP.NET HttpResponse not the WebApi.