5

Does anybody know where an iOS app can see the default headers that NSUrlRequest sets for an HTTP request?

Just creating NSUrlRequest with "http://.." NSURL and then asking: [request allHTTPHeaderFields] returns an empty dictionary. But I know that for example "Accept-Encoding" is set to "gzip". So I want to get all that fields and show them in a HTTP request demo.

I've also tried to swizzle [NSMutableURLRequest setValue:forHTTPHeaderField:], but it seems that it is not used by underlying API (NSURLRequest or NSURLConnection) to set those default fields I'm hunting for.

I'm making just a simple iOS demo which shows HTTP request and response information, so it doesn't really matters if it will be a public or private API used for that.

zubko
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3 Answers3

14

Your app cannot. It's done all down in CFNetwork - Communicating with HTTP Servers. I believe it just adds missing header values not supplied by NSURLRequest.

The defaults are:

  • USER-AGENT "AppName - Eng/1.0 CFNetwork/485.13.9 Darwin/10.7.0"
  • ACCEPT "*/*"
  • ACCEPT-LANGUAGE "en-us"
  • ACCEPT-ENCODING "gzip, deflate"
  • CONNECTION "keep-alive"
Black Frog
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5

hmm... maybe you might want to try within 

- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse

method in your custom nsurlconnection class. although the documentation mentions something about redirects, this is certainly worth looking into.

govi
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  • Nice shot, but unfortunately not 100% hit. – zubko Apr 20 '11 at 20:31
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    Indeed `-(NSURLRequest *)connection:willSendRequest: redirectResponse:` will be called for a simple request when no redirection is needed (despite official docs) and its header will have some fields at this stage: `{ Accept = "*/*"; Accept-Encoding" = "gzip, deflate"; Accept-Language" = "en-us";}` but there more: "Host", "User-Agent" and "Connection" which are set at some lower level - I've run a simple local HTTP server to see all of them. – zubko Apr 20 '11 at 20:40
2

That may be an overkill, but based on Matt Gallagher's blog post I've created even more simpler local HTTP listener and sent a separate [mutableCopy]ed request to it to be able to read and output all HTTP headers that this request has.

Better solution must be to setup a local HTTP request catcher, it must look nicer I think, but for the scope of simple demo just to show all sent/received headers this solution is OK.

zubko
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