I am working on Windows Service in visual studio 2017. In the rest api's call, getting exceptions while debugging code. Sometimes first 2 3 calls working after that getting exceptions.
System.Net.WebException: 'The remote server returned an error: (503)
Server Unavailable.'
The remote server returned an error: (429)
Unable to connect to the remote server
When calling same api's from Postman, getting response successfully.
This is my code
private void timer1_Tick(object sender, ElapsedEventArgs e)
{
WriteToFile("timer1_Tick method called..");
try
{
string jsonString = "";
string jsonstring2 = "";
string prodfetchurl = HOST;
var req = WebRequest.Create(prodfetchurl) as HttpWebRequest;
req.Method = "GET";
InitializeRequest(req);
req.Accept = MIME_TYPE;
//System.Threading.Thread.Sleep(5000);
var response = (HttpWebResponse)req.GetResponse();
WriteToFile("First service called...");
if (response.StatusCode == HttpStatusCode.OK)
{
Stream responseStream = response.GetResponseStream();
StreamReader responseReader = new StreamReader(responseStream);
jsonString = responseReader.ReadToEnd();
}
var deserialsseobj = JsonConvert.DeserializeObject<ProductList>(jsonString).Products.Where(i => i.Failed > 0).ToList();
foreach (var a in deserialsseobj)
{
var pid = a.ID;
string url = FailedDevicesUrl + pid.Value + "/failed";
var req2 = WebRequest.Create(url) as HttpWebRequest;
req2.Method = "GET";
InitializeRequest(req2);
req2.Timeout = 300000;
req2.Accept = MIME_TYPE;
var response1 = (HttpWebResponse)req2.GetResponse();
Stream responsestream2 = response1.GetResponseStream();
WriteToFile("Second service called...");
if (response1.StatusCode == HttpStatusCode.OK)
{
StreamReader responsereader1 = new StreamReader(responsestream2);
jsonstring2 = responsereader1.ReadToEnd();
}
var output = JsonConvert.DeserializeObject<List<FailedDeviceList>>(jsonstring2); // Will get List of the Failed devices
List<int> deviceids = new List<int>();
Reprocessdata reproc = new Reprocessdata();
Reprocessdata.DeviceId rprod = new Reprocessdata.DeviceId();
reproc.ForceFlag = true;
reproc.ProductID = pid.Value;
foreach (var dd in output)
{
rprod.ID = dd.DeviceId;
reproc.DeviceIds.Add(rprod);
}
// Reprocess the Product in Devices
var req3 = WebRequest.Create(ReprocessUrl) as HttpWebRequest;
req3.Method = "POST";
InitializeRequest(req3);
req3.Accept = MIME_TYPE;
req3.Timeout = 300000;
req3.ContentType = "application/json";
using (StreamWriter writer = new StreamWriter(req3.GetRequestStream()))
{
string json = new JavaScriptSerializer().Serialize(reproc);
writer.Write(json);
writer.Close();
}
System.Threading.Thread.Sleep(5000);
var response5 = (HttpWebResponse)req3.GetResponse();
WriteToFile("Third service called...");
if (response5.StatusCode == HttpStatusCode.OK)
{
string result;
using (StreamReader rdr = new StreamReader(response5.GetResponseStream()))
{
result = rdr.ReadToEnd();
}
}
}
response.Close();
}
catch (Exception ex)
{
WriteToFile("Simple Service Error on: {0} " + ex.Message + ex.StackTrace);
}
}
Methods used in above code
protected override void OnStart(string[] args)
{
base.OnStart(args);
timer1 = new System.Timers.Timer();
timer1.Interval = 60000; //every 1 min
timer1.Elapsed += new System.Timers.ElapsedEventHandler(timer1_Tick);
timer1.Enabled = true;
WriteToFile("Service has started..");
}
public void InitializeRequest(HttpWebRequest request)
{
request.Headers.Add("aw-tenant-code", API_TENANT_CODE);
request.Credentials = new NetworkCredential(USER_NAME, PASSWORD);
request.KeepAlive = false;
request.AddRange(1024);
}
When I contacted service provide they said everything fine from there side. Is this my code is buggy or windows service not reliable? How can I fix this issue?
Note: All APIS are working fine from Angular application using Visual Studio Code. It means my code is not working.
Edit1: Three below services I am using from this document of VMware.
private const string HOST = "https:host/api/mdm/products/search?";
private const string FailedDevicesUrl = "https:host/api/mdm/products/";
private const string ReprocessUrl = "https:host/api/mdm/products/reprocessProduct";
Response http code 429 indicates that you sending too many requests on target web service.
This means service you trying to send requests has a policies that blocks some requests by request-per-time limit.
Also I admit that external service can be manually configured to throw 403 code in specific cases that you can't know about. If that, this information can be explained in external service documentation... or not :)
What you can do with this?
Fit in limitations
You can make detailed research what limits target webservice has and set up your code to fit in this limitations. For example if service has limitation for receiving only one request per 10 minutes - you must set up your timer to send one request each 10 or more minutes. If documentation not provide such information - you can test it manually by finding some patterns with external service responses.
Use proxy
Every limitation policy based on information about requests senders. Usually this information consists of IP address of sender only. This means if you send 2 requests from two different IP addresses - limitation policy will perceive that like 2 different computers sending these requests. So you can find/buy/rent some proxy IP addresses and send requests through there on target web server.
How to connect through proxy in C# using WebRequest you can see in this answer.
Negotiate with external service provider
If you have possibility to communicate with external service developers or help center, you can ask their to reduce limitations for your IP address (if it static) or provide some mechanisms to avoid limitation policy for you. If for some reason they cannot provide this opportunity, at least you can ask detailed information about limitations.
Repetition mechanism
Some times 503 error code that is outer exception you received may be caused by service unavailable. It means that server can be under maintenance or temporary overloaded. So you can write repetition mechanism to make continious sending requests to server until it'll be accessible.
Polly library may help you with repetition mechanism creation
The inner error of that 503 is:
The remote server returned an error: (429)
HTTP 429 indicates too many requests. Maybe your upstream server can’t process all requests sent.
This can happen when you reached rate limiting / throttling value if you’re calling a third party API.
UPDATE
As per page 28 in the API docs, you could configure throttling when creating a new API. Check if the throttling is too small or maybe turn off the throttling and see if that could fix the error?
Related
I am sending cURL request using HttpClient through the method described here under.
The parameter used for this method are:
SelectedProxy = a custom class that stores my proxy's parameters
Parameters.WcTimeout = the timeout
url, header, content = the cURL request (based on this tool to convert to C# https://curl.olsh.me/).
const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;
ServicePointManager.SecurityProtocol = Tls12;
string source = "";
using (var handler = new HttpClientHandler())
{
handler.UseCookies = usecookies;
WebProxy wp = new WebProxy(SelectedProxy.Address);
handler.Proxy = wp;
using (var httpClient = new HttpClient(handler))
{
httpClient.Timeout = Parameters.WcTimeout;
using (var request = new HttpRequestMessage(new HttpMethod(HttpMethod), url))
{
if (headers != null)
{
foreach (var h in headers)
{
request.Headers.TryAddWithoutValidation(h.Item1, h.Item2);
}
}
if (content != "")
{
request.Content = new StringContent(content, Encoding.UTF8, "application/x-www-form-urlencoded");
}
HttpResponseMessage response = new HttpResponseMessage();
try
{
response = await httpClient.SendAsync(request);
}
catch (Exception e)
{
//Here the exception happens
}
source = await response.Content.ReadAsStringAsync();
}
}
}
return source;
If I am running this without proxy, it works like a charm.
When I send a request using a proxy which I tested first from Chrome, I have the following error on my try {} catch {}. Here is the error tree
{"An error occurred while sending the request."}
InnerException {"Unable to connect to the remote server"}
InnerException {"A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond [ProxyAdress]"}
SocketErrorCode: TimedOut
By using a Stopwatch I see that the TimedOut occurred after around 30 sec.
I tried a few different handler based on the following links What's the difference between HttpClient.Timeout and using the WebRequestHandler timeout properties?, HttpClient Timeout confusion or with the WinHttpHandler.
It's worth noting that WinHttpHandler allow for a different error code, i.e. Error 12002 calling WINHTTP_CALLBACK_STATUS_REQUEST_ERROR, 'The operation timed out'. The underlying reason is the same though it helped to target where it bugs (i.e. WinInet) which confirms also what #DavidWright was saying regarding that timeouts from HttpClient manages a different part of the request sending.
Hence my issue is coming from the time it takes to establish a connection to the server, which triggers the 30sec timeout from WinInet.
My question is then How to change those timeout?
On a side note, it's worth noting that Chrome, which uses WinInet, does not seem to suffer from this timeout, nor Cefsharp on which a big part of my app is based, and through which the same proxies can properly send requests.
So thanks to #DavidWright I understand a few things:
Before that the HttpRequestMessage is sent and the timeout from HttpClient starts, a TCP connection to the server is initiated
The TCP connection has its own timeout, defined at OS level, and we do not identified a way to change it at run time from C# (question pending if anyone want to contribute)
Insisting on trying to connect works as each try benefits from previous tries, though proper exception management & manual timeout counter needs to be implemented (I actually considered a number of tries in my code, assuming each try is around 30sec)
All this together ended up in the following code:
const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;
ServicePointManager.SecurityProtocol = Tls12;
var sp = ServicePointManager.FindServicePoint(endpoint);
sp.ConnectionLeaseTimeout = (int)Parameters.ConnectionLeaseTimeout.TotalMilliseconds;
string source = "";
using (var handler = new HttpClientHandler())
{
handler.UseCookies = usecookies;
WebProxy wp = new WebProxy(SelectedProxy.Address);
handler.Proxy = wp;
using (var client = new HttpClient(handler))
{
client.Timeout = Parameters.WcTimeout;
int n = 0;
back:
using (var request = new HttpRequestMessage(new HttpMethod(HttpMethod), endpoint))
{
if (headers != null)
{
foreach (var h in headers)
{
request.Headers.TryAddWithoutValidation(h.Item1, h.Item2);
}
}
if (content != "")
{
request.Content = new StringContent(content, Encoding.UTF8, "application/x-www-form-urlencoded");
}
HttpResponseMessage response = new HttpResponseMessage();
try
{
response = await client.SendAsync(request);
}
catch (Exception e)
{
if(e.InnerException != null)
{
if(e.InnerException.InnerException != null)
{
if (e.InnerException.InnerException.Message.Contains("A connection attempt failed because the connected party did not properly respond after"))
{
if (n <= Parameters.TCPMaxTries)
{
n++;
goto back;
}
}
}
}
// Manage here other exceptions
}
source = await response.Content.ReadAsStringAsync();
}
}
}
return source;
On a side note, my current implementation of HttpClient may be problematic in the future. Though being disposable, HttpClient should be defined at App level through a static, and not within a using statement. To read more about this go here or there.
My issue is that I want to renew the proxy at each request and that it is not set on a per request basis. While it explains the reasdon of the new ConnectionLeaseTimeout parameter (to minimize the time the lease remains open) it is a different topic
I have had the same problem with HttpClient. Two things need to happen for SendAsync to return: first, setting up the TCP channel over which the communication occurs (the SYN, SYN/ACK, ACK handshake, if you're familiar with that) and second getting back the data that constitutes the HTTP response over that TCP channel. HttpClient's timeout only applies to the second part. The timeout for the first part is governed by the OS's network subsystem, and it's quite difficult to change that timeout in .NET code.
(Here's how you can reproduce this effect. Set up a working client/server connection between two machines, so you know that name resolution, port access, listening, and client and server logic all works. Then unplug the network cable on the server and re-run the client request. It will time out with the OS's default network timeout, regardless of what timeout you set on your HttpClient.)
The only way I know around this is to start your own delay timer on a different thread and cancel the SendAsync task if the timer finishes first. You can do this using Task.Delay and Task.WaitAny or by creating a CancellationTokenSource with your desired timeone (which essentially just does the first way under the hood). In either case you will need to be careful about cancelling and reading exceptions from the task that loses the race.
In our Outlook COM add-in, we're making an API call to our server using the .NET HTTPWebRequest method. One of our customers is running into a System.Net.WebException with the message The remote name could not be resolved: 'mydomain.com' and WebExceptionStatus.NameResolutionFailure as the status. All the users from this particular customer's company are using outlook/the addin from behind a VPN so we are piggy-backing proxy configuration from IE in order to make the request.
Our API calls work for a period of time but then it randomly disconnects and then does not allow future requests to go through either. Once the users close and restart Outlook though, it seems to work just fine again without changing any network configuration or reconnecting to wifi etc.
Other posts like this suggested retrying with a sleep in between. We have added a retry mechanism with 3 attempts, each with a sleep in between but that has not resolved the intermitent issue.
Our domain is hooked up to an AWS Classic Load Balancer so mydomain.com actually resolves a CNAME record to an AWS static domain, pointing to the ELB. I'm not sure if that would have any impact on the request or routing it.
The strange part is we also have a web browser component that loads a web page in a sidebar from the exact same domain as the API calls. It works perfectly and loads a URL from the same domain. The users can also load the URL in their browsers without any issues. It just appears that the HTTPWebRequest is running into the domain resolution issue. We've checked that it's not just a matter of a weak wifi signal. Since they are able to use IE which has the same proxy config to access the site just fine, I don't think it's that.
We're at a loss for how to gracefully recover and have the request try again. I've looked into suggestions from this answer and this other answer, we'll be trying those next. Unfortunately, we are not able to make the requests use direct IP addresses as some of the other answers suggest. That also eliminates the ability to edit the hosts file to point straight to it. The reason is we can't assign a static IP on a classic ELB.
We're considering trying to set the host to use the CNAME record from AWS directly but this is going to cause SSL errors as it doesn't have a valid cert for the CNAME entry. Is there a way to get around that by masking it via a header, similar to the IP approach?
Feel free to ask for more information, I will do my best to provide it.
Any suggestions on what to try / troubleshoot are welcome!
Update: We’re targeting .NET v4.5
Here's the code
var result = string.Empty;
bool retrying = false;
int retries = 0;
HttpWebRequest webRequest = null;
try
{
ServicePointManager.ServerCertificateValidationCallback =
CertificateCheck;
ServicePointManager.MaxServicePoints = 4;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
retry:
webRequest = (HttpWebRequest)WebRequest.Create(uriParam);
webRequest.Timeout = 120000;
webRequest.Method = "POST";
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Accept = acceptParam;
webRequest.Headers.Add("Cookie", cookieParam);
webRequest.UseDefaultCredentials = true;
webRequest.Proxy = null;
webRequest.KeepAlive = true; //default
webRequest.ServicePoint.ConnectionLeaseTimeout = webRequest.Timeout;
webRequest.ServicePoint.MaxIdleTime = webRequest.Timeout;
webRequest.ContentLength = dataParam.Length;
using (var reqStream = webRequest.GetRequestStream())
{
reqStream.Write(dataParam, 0, dataParam.Length);
reqStream.Flush();
reqStream.Close();
}
try
{
using (WebResponse webResponse = webRequest.GetResponse())
{
using (var responseStream = webResponse.GetResponseStream())
{
if (responseStream != null)
{
using (var reader = new StreamReader(responseStream))
{
result = reader.ReadToEnd();
}
}
}
webResponse.Close();
}
}
catch (WebException)
{
if (retrying && retries == 3)
{
//don't retry any more
return string.Empty;
}
retrying = true;
retries++;
webRequest.Abort();
System.Threading.Thread.Sleep(2000);
goto retry;
}
}
catch (Exception ex)
{
Log.Error(ex);
result = string.Empty;
}
finally
{
webRequest?.Abort();
}
return result;
I've been working on a project which makes use of an RTC API and forms authentication. I've hit a bit of bizarre behaviour and I just can't figure this one out.
The scenario that has played out to date is that I can successfully run this project locally end to end. That is, this specific piece of code can:
Contact the remote server and successfully authenticate
After authentication I'm able to pass XML to update a ticket in RTC
The problem starts when I publish to our IIS (7.5) server. All works fine right up until the last .GetResponse call which uses a PUT method to pass my XML to update the ticket in RTC. I keep getting 'The operation has timed out'.
I've spent literally days trying to figure this one out doing all manner of things but nothing has proved useful.
As a test I changed the PUT method on the second call to a GET. And it works! If I used a PUT with the .AllowAutoRedirect = false it works in that I get a response back, but then nothing happens on the RTC side so the request is clearly being ignored. I also noticed that the status being returned is marked as 'Found' instead of 'OK'.
Some people thought at this stage perhaps it was a lack of connectivity between the remote server and the web server. This wouldn't be the case as authentication works and this happens against the same server. I have also manually passed the XML / PUT call using the RESTClient on the web server which was accepted fine.
I just can't understand why it works end to end when running locally, but plays up once deployed to IIS?
I tried using log tracing and I'm not entirely sure if I'm getting anything useful from it. It might be totally unrelated but I can see this in the log that is generated on the IIS server:
<EventData>
<Data Name="ContextId">{00000000-0000-0000-12AF-0080000000F8}</Data>
<Data Name="ModuleName">ManagedPipelineHandler</Data>
<Data Name="Notification">128</Data>
<Data Name="HttpStatus">500</Data>
<Data Name="HttpReason">Internal Server Error</Data>
<Data Name="HttpSubStatus">0</Data>
<Data Name="ErrorCode">0</Data>
<Data Name="ConfigExceptionInfo"></Data>
</EventData>
As I say, I'm not sure if this is even related to the problem I'm having, but rather than ignore it I thought I'd share.
Code that forms the call (excuse the standard of coding, it's work in progress and got messy trying out different things to fix this problem)
//Setup webrequest
CookieContainer _cookies = new CookieContainer();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(getPath);
var test44 = test4.ToString();
request.CookieContainer = _cookies;
request.ContentType = "application/rdf+xml";
request.Accept = "application/rdf+xml";
request.Method = "PUT";
request.AllowAutoRedirect = true;
request.AllowWriteStreamBuffering = true;
request.Timeout = 40000;
byte[] bytes = Encoding.ASCII.GetBytes(test44);
request.ContentLength = bytes.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(bytes, 0, bytes.Length);
dataStream.Close();
//Pass request
logger.Info("Made it up to start of RTC request for secure document.");
using (HttpWebResponse getrespn = requestSecureDocument(request, "https://myserver:9100/jazz", "username", "pass", test44))
{
//Stream ReceiveStream = getrespn.GetResponseStream();
// Encoding encode = System.Text.Encoding.GetEncoding("utf-8");
//StreamReader readStream = new StreamReader(ReceiveStream);
//response = readStream.ReadToEnd();
getrespn.Close();
}
The segment of code which interacts with the RTC server (based on the example from: https://nkumar83.wordpress.com/2013/06/13/consuming-rtc-rational-team-concert-oslc-apis-using-c-post-1-authentication/ with my own tweaks):
public static HttpWebResponse requestSecureDocument(HttpWebRequest _requestItem, string _rtcServerURL, string _userName, string _password, string passXml)
{
try
{
//FormBasedAuth Step 1: Request the resource
HttpWebRequest _request = (HttpWebRequest)WebRequest.Create(_requestItem.RequestUri);
_request.CookieContainer = _requestItem.CookieContainer;
//store the response in _docResponse variable
HttpWebResponse _docResponse = (HttpWebResponse)_request.GetResponse();
//HttpStatusCode.OK indicates that the request succeeded
if (_docResponse.StatusCode == HttpStatusCode.OK)
{
//X-com-ibm-team... header signifies form based authentication is being used
string _rtcAuthHeader = _docResponse.Headers["X-com-ibm-team-repository-web-auth-msg"];
if ((_rtcAuthHeader != null) && _rtcAuthHeader.Equals("authrequired"))
{
_docResponse.GetResponseStream().Flush();
_docResponse.Close();
//Prepare form for authentication
HttpWebRequest _formPost = (HttpWebRequest)WebRequest.Create(_rtcServerURL + "/j_security_check");
_formPost.Method = "POST";
_formPost.Timeout = 30000;
_formPost.CookieContainer = _request.CookieContainer;
_formPost.Accept = "text/xml";
_formPost.ContentType = "application/x-www-form-urlencoded";
string _authString = "j_username=" + _userName + "&j_password=" + _password;
Byte[] _outBuffer = Encoding.UTF8.GetBytes(_authString);
_formPost.ContentLength = _outBuffer.Length;
Stream _str = _formPost.GetRequestStream();
_str.Write(_outBuffer, 0, _outBuffer.Length);
_str.Close();
//FormBasedAuth Step 2: Submit the login form and get response
HttpWebResponse _formResponse = (HttpWebResponse)_formPost.GetResponse();
_rtcAuthHeader = _formResponse.Headers["X-com.ibm-team.repository-web-auth-msg"];
//Check if auth failed
if ((_rtcAuthHeader != null) && _rtcAuthHeader.Equals("authfailed"))
{
//auth fialed
var fail = "";
}
else
{
//login successful
//FormBasedAuth Step 3: Resend the request for the protected resource
_formResponse.GetResponseStream().Flush();
_formResponse.Close();
using (HttpWebResponse getresp = (HttpWebResponse)_requestItem.GetResponse()) *** THIS IS TH LINE WHICH THROWS THE EXCEPTION ***
{
return getresp;
}
}
}
}
return _docResponse;
}
catch (WebException e)
{
var filePath = AppDomain.CurrentDomain.GetData("DataDirectory") + #"/trapA.xml";
using (StreamWriter writer = new StreamWriter(filePath, true))
{
writer.WriteLine("Message: Failed to trigger getresponse successfully: " + e);
}
}
return null;
}
Hope someone out there can help :o)
Well I'm pleased to say I've finally got to the bottom of this one. Turns out the problem wasn't anything to do with IIS and does actually work when published 'if' I'm not using the RTC client to make updates to a ticket.
The short story is that our RTC client uses a custom script to post out to our web api. However the RTC client appears to put a record lock on the ticket your trying to update which is persisted until a response from our API is provided. Of course this can't happen because part of the response is to confirm if the update was successful which can't happen due to the lock made by the RTC client.
The solution was to get the call in from RTC closed as quickly as possible. So the segment of code which authenticates and calls back out to RTC to make updates is now wrapped around with some new code to create a new thread. This has allowed the connection to be closed in about 5 seconds, all the while our app continues to make the necessary calls to complete the transaction.
Thread t = new Thread(() = > {
//code here
}
I may well be approaching this incorrectly, but what I'm trying to do is consume a GET request so I can manipulate the response into a format that I want. I need to be able to launch this from a browser, so I thought about building another RESTful service for this purpose.
i.e. Service ABC returns a string using a GET request. I want to take that string, do some manipulation and return it. I still need to be able to launch from a browser, so what I'm planning is to create a RESTful service XYZ, where the GET request in XYZ launches a call to the GET request of ABC, takes that response, converts it into my collection, and returns that collection. I'll then display in MVC.
Firstly: is this a dumb choice? I don't know a lot about different types of services.
Secondly: I have been able to get the ABC service data using a Console client, but not using a web-based client or service. Is this to be expected?
Code:
string webPath = #"http://ABCService.co.uk/";
string methodCall = #"methodABC/uid";
RestClient restClient = new RestClient(webPath);
RestRequest request = new RestRequest(methodCall, Method.GET);
var restResponse = restClient.Execute(request);
var content = restResponse.Content;
This works fine in the console (and I've actually been able to get the data just using a WebClient too), but neither method works from inside an MVC controller or service. I just get this as an ErrorException in restResponse:
Exception: "{"Unable to connect to the remote server" InnerException
= {"A connection attempt failed because the connected party did not properly respond after a period of time, or established connection
failed because connected host has failed to respond 80.64.52.36:80"}
Service ABC is up and running, can be accessed from a browser and console app. Note that I have no ability to alter any settings within Service ABC.
Many thanks
I resolved this by setting the proxy to null, rather than using a default proxy.
public string ReadWebReport(string path)
{
string str = String.Empty;
HttpWebRequest Request = WebRequest.Create(path) as HttpWebRequest;
Request.Method = "GET"; //Or PUT, DELETE, POST
Request.ContentType = "application/x-www-form-urlencoded";
Request.Proxy = null; //<-- inserted line
using (HttpWebResponse Response = Request.GetResponse() as HttpWebResponse)
{
if (Response.StatusCode != HttpStatusCode.OK)
throw new Exception("The request did not complete successfully and returned status code " + Response.StatusCode);
using (StreamReader Reader = new StreamReader(Response.GetResponseStream()))
{
str = Reader.ReadToEnd();
}
}
return str;
}
I am writing a program. my program receive data from a server through HTTP protocol. the data will be pushed by server to my program.
I tried to use WebRequest, but only received one session of data.
How can i keep the connection alive, to receive the data from server continuosly,
Any help is appreciated.
the following is the SDK document:
Under the authorization of GUEST or ADMIN, it is possible to get the series of live images
(Server push). To get the images, send the request to “/liveimg.cgi?serverpush=1” as shown
in the Figure. 2-1-1.
When the camera receives the above request from the client, it sends the return as shown
in the Figure. 2-2.
Each JPEG data is separated by “--myboundary”, and “image/jpeg” is returned as
“Content-Type” header, after “--myboundary”. For “Content-Length” header, it returns the
number of bytes in the --myboundary data (excluding “--myboundary”, each header, and
\r\n as delimiter). After the “Content-Length” header and “\r\n” (delimiter), the actual
data will be sent.
This data transmission will continue until the client stop the connection (disconnect), or
some network error occurs.
int len;
string uri = #"http://192.168.0.2/liveimg.cgi?serverpush=1";
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(uri);
req.Credentials = new NetworkCredential("admin", "admin");
req.KeepAlive = true;
string line = "";
HttpWebResponse reply = (HttpWebResponse)req.GetResponse();
Stream stream = reply.GetResponseStream();
System.Diagnostics.Debug.WriteLine(reply.ContentType);
StreamReader reader = new StreamReader(stream);
do
{
line = reader.ReadLine();
System.Diagnostics.Debug.WriteLine(line);
System.Threading.Thread.Sleep(300);
} while (line.Length>0);
You can keep an HTTP connection open for an extended period of time, if the server supports doing so. (As already mentioned, this will significantly limit the number of simultaneous users you can support.)
The server will need to be set Response.Buffer=false, and have an extended ScriptTimeout (I'm assuming your using ASP.NET on the server side). Once you do that, your page can keep sending Response.Write data as needed until whatever it is doing is done.
Your client will need to process the incoming Response before the connection is complete rather than blocking for the complete response.
You may want to take a look at StreamHub Push Server - its a popular Comet server and has an .NET Client SDK which allows you to receive real-time push updates in C# (or VB / C++).
If I'm understanding you correctly, your server is going to respond to some event by sending data to your client outside of the client making a request/response. Is this correct? If so, I wouldn't recommend trying to keep the connection open unless you have a very small number of clients -- there are a limited number of connections available, so keeping them open may rapidly result in an exception.
Probably the easiest solution would be to have the clients poll periodically for new data. This would allow you to use a simple server and you'd only have to code a thread on the client to request any changes or new work once every minute or thirty seconds or whatever your optimal time period is.
If you truly want to have the server notify the clients proactively, without them polling, then you'll have to do something other than a simple web server -- and you'll also have to code and configure the client to accept incoming requests. This may be difficult if your clients are running behind firewalls and such. If you go this route, WCF is probably your best choice, as it will allow you to configure server and client appropriately.
You need to get a cookie from IP cam and include that cookie in header of your next HttpWebRequest. Otherways it will always try to redirect you to "index.html".
Here is how you can do it...
BitmapObject is a class that serves as a container for Jpeg image, current date and eventual error text. Once a connection is established it will pool an image every 200 ms. Same should be applicable for continuous image stream obtained through "serverpush".
public void Connect()
{
try
{
request = (HttpWebRequest)WebRequest.Create("Http://192.168.0.2/index.html");
request.Credentials = new NetworkCredential(UserName,Password);
request.Method = "GET";
response = (HttpWebResponse)request.GetResponse();
WebHeaderCollection headers = response.Headers;
Cookie = headers["Set-Cookie"];//get cookie
GetImage(null);
}
catch (Exception ex)
{
BitmapObject bitmap = new BitmapObject(Properties.Resources.Off,DateTime.Now);
bitmap.Error = ex.Message;
onImageReady(bitmap);
}
}
private Stream GetStream()
{
Stream s = null;
try
{
request = (HttpWebRequest)WebRequest.Create("http://192.168.0.2/liveimg.cgi");
if (!Anonimous)
request.Credentials = new NetworkCredential(UserName, Password);
request.Method = "GET";
request.KeepAlive = KeepAlive;
request.Headers.Add(HttpRequestHeader.Cookie, Cookie);
response = (HttpWebResponse)request.GetResponse();
s = response.GetResponseStream();
}
catch (Exception ex)
{
BitmapObject bitmap = new BitmapObject(Properties.Resources.Off,DateTime.Now);
bitmap.Error = ex.Message;
onImageReady(bitmap);
}
return s;
}
public void GetImage(Object o)
{
BitmapObject bitmap = null;
stream = GetStream();
DateTime CurrTime = DateTime.Now;
try
{
bitmap = new BitmapObject(new Bitmap(stream),CurrTime);
if (timer == null)//System.Threading.Timer
timer = new Timer(new TimerCallback(GetImage), null, 200, 200);
}
catch (Exception ex)
{
bitmap = new BitmapObject(Properties.Resources.Off, CurrTime);
bitmap.Error = ex.Message;
}
finally
{
stream.Flush();
stream.Close();
}
onImageReady(bitmap);
}
If you are using a standard web server, it will never push anything to you - your client will have to periodically pull from it instead.
To really get server push data you have to build such server yourself.