So, to confirm, you've implemented the
urlSession(_:dataTask:didReceive:)
delegate callback and it’s not getting called, right?
Weird. I tried this out here in my office and, while I saw some weird stuff, I definitely get the response data back from the server.
Consider the test code pasted in at the end of this post. When I run
startIdentity()
, it prints this:
| 2017-05-02 10:01:35.288 xxsi[2506:145728] success, status: 200 |
| 2017-05-02 10:01:35.288 xxsi[2506:145728] response: { |
| args = { |
| }; |
| data = ""; |
| files = { |
| }; |
| form = { |
| greetings = "Hello Cruel World!"; |
| salutations = "Goodbye Cruel World!"; |
| }; |
| headers = { |
| Accept = "*/*"; |
| "Accept-Encoding" = "gzip, deflate"; |
| "Accept-Language" = "en-us"; |
| Connection = close; |
| "Content-Length" = 383; |
| "Content-Type" = "multipart/form-data; boundary=Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278"; |
| Host = "httpbin.org"; |
| "User-Agent" = "xxsi/1.0 CFNetwork/811.4.18 Darwin/16.5.0"; |
| }; |
| json = "<null>"; |
| origin = "88.97.8.212"; |
| url = "https://httpbin.org/post"; |
| } |
As expected:
Now look at when happens when I run
startChunked()
:
| 2017-05-02 10:01:40.811 xxsi[2506:145728] data chunk: <7b0a2020 …> |
| 2017-05-02 10:01:40.811 xxsi[2506:145728] success, status: 200 |
| 2017-05-02 10:01:40.812 xxsi[2506:145728] response: { |
| args = { |
| }; |
| data = ""; |
| files = { |
| }; |
| form = { |
| }; |
| headers = { |
| Accept = "*/*"; |
| "Accept-Encoding" = "gzip, deflate"; |
| "Accept-Language" = "en-us"; |
| Connection = close; |
| "Content-Type" = "multipart/form-data; boundary=Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278"; |
| Host = "httpbin.org"; |
| "Transfer-Encoding" = Chunked; |
| "User-Agent" = "xxsi/1.0 CFNetwork/811.4.18 Darwin/16.5.0"; |
| }; |
| json = "<null>"; |
| origin = "88.97.8.212"; |
| url = "https://httpbin.org/post"; |
| } |
There’s two things to note here:
As before, the server has sent me some JSON and I’ve been able to parse and print it
The server did not recognise my form data.
AFAICT I’ve done nothing wrong here. Looking at a packet trace of what I sent on the wire, the only difference between the two requests is the transfer encoding. The identity request uses no transfer encoding and the chunked request uses a transfer encoding of
Chunked
. This is both expected (NSURLSession doesn’t know the length of the body stream and thus
has to use chunked encoding) and correct (HTTP 1.1 requires that the server support chunked encoding). However, it’s clear that
httpbin.org
is not handling this properly.
Coming back to your situation, I’m not sure what this means for you. To do a streamed upload you’re going to have to use chunked encoding. I presume that the server you’re talking to will accept that, but it’s hard to know for sure because I don’t control the server.
IMO your best way forward here is to:
Learn how to use packet tracing technologies so you can see exactly what’s happening on the wire
Find a working client (perhaps the server’s SDK includes some sample code) and compare its on-the-wire behaviour to that of your client’s
I discuss this idea in depth in my Debugging HTTP Server-Side Errors post.
Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"
| import UIKit |
| |
| class MainViewController : UITableViewController, URLSessionDataDelegate { |
| |
| var session: URLSession! |
| var accumulated = Data() |
| |
| override func viewDidLoad() { |
| super.viewDidLoad() |
| let config = URLSessionConfiguration.default |
| config.requestCachePolicy = .reloadIgnoringLocalCacheData |
| self.session = URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue.main) |
| } |
| |
| override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { |
| switch (indexPath.section, indexPath.row) { |
| case (0, 0): self.startIdentity() |
| case (0, 1): self.startChunked() |
| default: fatalError() |
| } |
| self.tableView.deselectRow(at: indexPath, animated: true) |
| } |
| |
| func startIdentity() { |
| self.session.uploadTask(with: MainViewController.testRequest, from: MainViewController.testBody) { (data, response, error) in |
| MainViewController.print(error: error, response: response, body: data) |
| }.resume() |
| } |
| |
| func startChunked() { |
| self.accumulated.removeAll() |
| self.session.uploadTask(withStreamedRequest: MainViewController.testRequest).resume() |
| } |
| |
| func urlSession(_ session: URLSession, task: URLSessionTask, needNewBodyStream completionHandler: @escaping (InputStream?) -> Void) { |
| let bodyStream = InputStream(data: MainViewController.testBody) |
| completionHandler(bodyStream) |
| } |
| |
| func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) { |
| NSLog("data chunk: %@", data as NSData) |
| self.accumulated.append(data) |
| } |
| |
| func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) { |
| MainViewController.print(error: error, response: task.response, body: self.accumulated) |
| } |
| |
| static let testRequest: URLRequest = { |
| var result = URLRequest(url: URL(string: "http://httpbin.org/post")!) |
| result.httpMethod = "POST" |
| result.setValue("multipart/form-data; boundary=Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278", forHTTPHeaderField: "Content-Type") |
| return result |
| }() |
| |
| static let testBody: Data = { |
| var result = Data() |
| |
| func add(_ string: String) { |
| result.append(string.data(using: String.Encoding.utf8)!) |
| } |
| |
| |
| add("\r\n") |
| add("--Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278\r\n") |
| add("Content-Disposition: form-data; name=\"greetings\"\r\n") |
| add("Content-Type: text/plain; charset=UTF-8\r\n") |
| add("\r\n") |
| add("Hello Cruel World!") |
| add("\r\n") |
| add("--Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278\r\n") |
| add("Content-Disposition: form-data; name=\"salutations\"\r\n") |
| add("Content-Type: text/plain; charset=UTF-8\r\n") |
| add("\r\n") |
| add("Goodbye Cruel World!") |
| add("\r\n") |
| add("--Boundary-0DFADA5A-6C2F-4FD9-9E92-CCBB2A100278--\r\n") |
| add("\r\n") |
| |
| |
| return result |
| }() |
| |
| static func print(error: Error?, response: URLResponse?, body: Data?) { |
| if let error = error as NSError? { |
| NSLog("failed, error: %@ / %d", error.domain, error.code) |
| } else { |
| let response = response! as! HTTPURLResponse |
| let body = body! |
| |
| NSLog("success, status: %d", response.statusCode) |
| |
| if let root = try? JSONSerialization.jsonObject(with: body, options: []) { |
| NSLog("response: %@", "\(root)") |
| } else { |
| NSLog("response not parsed") |
| } |
| } |
| } |
| } |
