My dart server has a function which receives a POST request from a client. I want to use information from that request to issue a POST to another server, then use the response from this other server to send a response back to the original client request. When I issue my POST to the other server, it closes the stream on the inbound client request and I can no longer respond. Is there a way to keep the request stream 'alive' while I do a POST? Or, is there another way to do this? I did try to issue the POST on a different Isolate, but that didn't help, the http request stream is still getting closed.
void postRequest(HttpRequest request) async {
final endPoint = 'https://www.anotherserver.com/information';
final client = Client();
final data = request.headers.value('data'); // Get data from client
final response = client.post(endPoint, body: data); // Send data to other server
// Do stuff with the response from endPoint server
// For simplicity of this example, just send back the response body back to the client
// This write call to the request causes an "Stream Sink Closed" exception
// It appears the POST call to the endPoint server, caused the client request stream
// to get closed.
request.response.write(response.body);
await request.response.flush();
await request.response.close();
}
I was not awaiting the client.post.... I need to do a better job of watching out for that.
Related
I am using the TIdHTTP component and it's GET function.
The GET function sends a complete request, which is fine.
However I would like to spare/save some traffic from a GET response and only want to receive the Responsecode which is in the first "line" of a HTTP response.
Is there a possibility of disconnecting the connection in order to save traffic from any further content?
As mentioned, I only need the responsecode from a website.
I alternatively thought about using Indy's TCP component (with SSL IOHandler) and craft an own HTTP Request Header and then receive the responsecode and disconnect on success - but I don't know how to do that.
TIdHTTP has an OnHeadersAvailable event that is intended for this very task. It is triggered after the response headers have been read and before the body content is read, if any. It has a VContinue output parameter that you can set to False to cancel any further reading.
Update: Something I just discovered: When setting VContinue=False in the OnHeadersAvailable event, TIdHTTP will set Response.KeepAlive=False and skip reading the response body (OK so far), but after the response is done being processed, TIdHTTP checks the KeepAlive value, and the property getter returns True if the socket hasn't been closed on the server's end (HTTP 1.1 uses keep-alives by default). This causes TIdHTTP to not close its end of the socket, and will leave any response body unread. If you then re-use the same TIdHTTP object for a new HTTP request, it will end up processing any unread body data from the previous response before it sees thee response headers of the new request.
You can work around this issue by setting the Request.Connection property to 'close' before calling TIdHTTP.Get(). That tells the server to close its end of the socket connection after sending the response (although, I just found that when requesting an HTTPS url, especially after an HTTP request directs to HTTPS, TIdHTTP clears the Request.Connection value!). Or, simply call TIdHTTP.Disconnect() after TIdHTTP.Get() exits.
I have now updated TIdHTTP to:
no longer clear the Request.Connection when preparing an HTTPS request.
close its end of the socket connection if either:
OnHeadersAvailable returns VContinue=False
the Request.Connection property (or, if connected to a proxy, the Request.ProxyConnection property) has been set to 'close', regardless of the server's response.
Usually you would use TIdHttp.Head, because HEAD requests are intended for doing just that.
If the server does not accept HEAD requests like in OP's case, you can assign the OnWorkBegin event of your TIdHttp instance, and call TIdHttp(Sender).Disconnect; there. This immediately closes the connection, the download does not continue, but you still have the meta data like response code, content length etc.
I'm getting strange errors in ASP.NET Core when calling Web API that I have created for the application. GET requests go through fine and return all of the data that they should, but my POST/PUT commands all return a 502, specifically from the MVC application. I can call the API's from Postman and get a proper response and the object is created in the database.
502 - Web server received an invalid response while acting as a
gateway or proxy server. There is a problem with the page you are
looking for, and it cannot be displayed. When the Web server (while
acting as a gateway or proxy) contacted the upstream content server,
it received an invalid response from the content server.
I am impersonating an Integrated Windows Login with the following code for all web requests to the API:
async Task Action()
{
response = await _service.CreateIncident(model);
}
await WindowsIdentity.RunImpersonated(identity.AccessToken, Action);
CreateIncident(model):
using (var client = new HttpClient(new HttpClientHandler { UseDefaultCredentials = true }))
{
var newIncident = new StringContent(JsonConvert.SerializeObject(model), Encoding.UTF8, "application/json");
var response = await client.PostAsync(hostUri, newIncident);
return response;
}
There is also one GET Request that I make through Ajax to get an incremented ID to display to the user before they create their new Incident that returns a 502 Bad Gateway as well. Is this an IIS Setting that is incorrect?
If you use WindowsIdentity.RunImpersonated and an asynchronous function, it will not work. You must be synchronous when doing non-GET requests. I have updated my GitHub issue, I'm hoping to get this bug addressed. If you are a future visitor to this topic, you can see where this ended up here.
I think it also depends on the size of the data. Smaller packages work, larger ones don't.
I'm trying to implementing a proxy server with Dart: a web app running on the browser makes a request to my dart server app (proxy server) running locally, and then the proxy server makes a request to the external server. I then add CORS headers to the response that is going to be sent back to the client (web app).
Here's how I implemented the proxy server:
import 'dart:io';
import 'dart:convert';
main() async {
var server = await HttpServer.bind(InternetAddress.ANY_IP_V6, 8080);
print('Server listening on port ${server.port}...');
var client = 0;
HttpClient proxy;
await for (HttpRequest request in server) {
print('Request received from client ${++client}.');
// Adds CORS headers.
request.response.headers.add('Access-Control-Allow-Origin', '*');
proxy = new HttpClient()
..getUrl(Uri.parse('http://example.com/'))
// Makes a request to the external server.
.then((HttpClientRequest proxyRequest) => proxyRequest.close())
// Sends the response to the web client.
.then((HttpClientResponse proxyResponse) =>
proxyResponse.transform(UTF8.decoder).listen((contents) =>
request.response
..write(contents)
..close()
));
print('Response sent to client $client.');
}
}
This works fine most of the times, but sometimes the client only receives part of the response. I think sometimes the request.response.close() is being executed before the request.response.write(contents) finished executing, and so the response is sent before it has finished writing the contents.
Is there any way to solve this and only send the response once the contents have been written? Thanks.
You close the response after you receive the first chunk of data (..close()) . You should remove the close() from there and listen to the close event of the proxyResponse stream and close the response from there.
I'm trying to send an XMLHttpRequest object to my Rails server but the headers are causing my function to stop. Here are my observations:
When I comment out the 3 lines of code that set the headers, then xhr.readyState will eventually equal 4 (alert boxes within the anonymous function fire off).
If any one of the 3 header lines are uncommented, then the xhr object never changes state (none of the alert boxes ever fire off).
function saveUserProfile(){
var user_email = $('#userEmail_box').val();
var xhr = new XMLHttpRequest();
xhr.onreadystatechange=function(){
if (xhr.readyState==4 && xhr.status==200)
{
alert("Yes: " + xhr.readyState);
}
alert("No: " + xhr.readyState);
}
var method = 'POST';
var params = 'userEmail=user_email';
var url = 'http://localhost:3000/xhr_requests.json';
var async = true;
//Need to send proper header information with POST request
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.setRequestHeader('Content-length', params.length);
xhr.setRequestHeader('Connection', 'close');
xhr.open(method, url, async);
xhr.send(params);
}
My three questions are:
What do I need to change in the code above in order to send data through the POST method?
I'm under the impression that the POST method requires some headers to be sent but am not clear about which ones though "xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');" seems to be one that is often mentioned in references. Can somebody help me understand a) why headers need to be sent and b) which ones need to be sent?
I'm using a rails server and am developing locally. Ultimately, this code will be executed on the client side of a mobile device which will go to a hosted rails server for passing and receiving data. Are there limitations with using the POST method with a rails server? Keep in mind that I plan to use JSON when sending information to the client from the server.
Thanks!
UPDATE: The headers should come AFTER the opening the xhr request but BEFORE sending it:
xhr.open(method, url, async);
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.setRequestHeader('Content-length', params.length);
xhr.setRequestHeader('Connection', 'close');
xhr.send(params);
Hope this post saves somebody else 4 hours.
Does your web page with the JavaScript code also live on localhost:3000? If not, this is considered a cross-domain request, and your server will need to return special headers. So you have two options:
1) Host the web page on the same domain as the server, which will make this a same-domain request.
2) Have your server return the appropriate CORS headers. You can learn more about CORS here: http://www.html5rocks.com/en/tutorials/cors/
Is there any way to accept POST type requests without using Nerve lib in Node.js?
By default the http.Server class of Node.js accepts any http method.
You can get the method using request.method (api link).
Example:
var sys = require('sys'),
http = require('http');
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.write(request.method);
response.end();
}).listen(8000);
sys.puts('Server running at http://127.0.0.1:8000/');
This will create a simple http server on the port 8000 that will echo the method used in the request.
If you want to get a POST you should just check the request.method for the string "POST".
Update regarding response.end:
Since version 0.1.90, the function to close the response is response.end instead of response.close. Besides the name change, end can also send data and close the response after this data is sent unlike close. (api example)