iOS: Two requests from one call? - ios

Question

I'm writing an iPad app that needs to communicate with a backend server. The first order of business in using this backend is to login, and for this the server has a URL that we can POST to, which I do like this:
// Create the request.
NSString* loginURL = #"http://foo.local/signature/service/auth/rest/firewall/login";
NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:loginURL]];
NSString* credentials = #"{\"userName\":\"foo2#foolinator.com\", \"password\":\"password\"}";
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:[credentials dataUsingEncoding:NSASCIIStringEncoding
allowLossyConversion:YES]];
// Logging in...
NSError* error = nil;
NSURLResponse* response;
NSData* result = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*) response;
NSString* responseString = [NSHTTPURLResponse localizedStringForStatusCode:[httpResponse statusCode]];
NSLog(#"Response String is: %#\n", responseString);
NSLog(#"Header fields are: %#\n", [httpResponse allHeaderFields]);
What's odd is that the response I'm getting is Error 405: Method Not Allowed. I would've expected this if I was doing a GET, but I'm doing a POST.
I installed WireShark to examine the HTTP requests and it seems that there's actually two being made. The first one, is a POST call, and the server returns some cookie information as a response, and then a second GET call, which is what the code above gets back.
Why does this happen? Is it something to do with the response from the server the first time?

Answer 1

While you research your web service's login API, a couple of unrelated observations:
You should be sending this asynchronously if doing this from the main queue. Never issue synchronous network requests from the main queue. If you do this synchronously on the main queue (a) you risk having the iOS watch-dog process kill your app, which happens if the main queue becomes unresponsive while some synchronous network request is being processed; and (b) it's a bad UX to simply freeze an app during a network request ... if you need, disable the UI and show an indeterminate progress indicator (a UIActivityIndicatorView) while the network request is in progress.
You should probably be setting a value forHTTPHeaderField for Content-Length. It's probably not required, but it's good practice.
You probably should not be using a string with the JSON with the userid and password, but rather you should probably build this from a NSDictionary using something like NSJSONSerialization. As it is, if your password, for example, had any characters that needed to be escaped (e.g. a quotation mark), the existing code might not work. Using NSJSONSerialization is an easy way to ensure that your JSON is properly formatted.
You probably should not be sending a password in plaintext in your JSON request. At the very least, I hope your server employs HTTPS.
Anyway, with these observations, assuming your server really is expecting a JSON request, I might suggest something like:
// hopefully your production server is employing HTTPS
NSString *loginURL = #"https://foo.local/signature/service/auth/rest/firewall/login";
// use NSJSONSerialization to create JSON rather than building it in a NSString
NSDictionary *postDictionary = #{#"userName": userName, #"password": password}; // assuming you have NSString variables, `userName` and `password`
NSError *error = nil;
NSData *postData = [NSJSONSerialization dataWithJSONObject:postDictionary options:0 error:&error];
NSAssert(postData, #"dataWithJSONObject failed: %#", error);
// when creating request, also set Content-Length
NSURL *url = [NSURL URLWithString:loginURL];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:postData];
[request setValue:#"application/json; charset=utf-8" forHTTPHeaderField:#"Content-Type"];
// issue request asynchronously
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
if (connectionError) {
NSLog(#"sendAsynchronousRequest error: %#", connectionError);
return;
}
// process the server response here
}];
You might still want to use a NSURLConnectionDataDelegate/NSURLConnectionDelegate based request (you can identify redirects, challenges, cancel it if you need, etc.), but the above might be a good start at an asynchronous JSON-based request.