Max parameter size for NSData / setHTTPBody?

Question

My iPad app sends a list of files as a string parameter, fileList to a web method like this:

NSString *post = [NSString stringWithFormat:@"sessionID=%@&fileList=%@&dateTime=%@&userID=%@", sessionID, fileList, timeOpened, userID];    
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *comparisonURLString = SERVER_COMPARE_URL_STRING;
NSURL *comparisonURL = [NSURL URLWithString:comparisonURLString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:comparisonURL];

NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];

[request setHTTPMethod:@"POST"];
[request addValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:postData];

When the list of files is above a certain size, it seems to be truncated. I couldn't find anything about a maximum size in the apple documentation. Also, the subsequent parameters seem to be received OK regardless but before I discount this as a possible source of the problem, I was wondering if anyone knows if there is such a limitation?

The server is running IIS7, and the webConfig maxRequestLength is set to 1048576.

-EDIT-

Source of the Problem:

I created a webmethod that only takes in the entire POST as a parameter and it removes everything after an ampersand (&) so I think this may be where the problem lies, rather than parameter size.

@trojanfoe: Yes, sorry. I've edited to question to include that code. — Robert, Feb 28 '13 at 10:41
I don't see where `postLength` is created. Also are you setting the `Content-Type` HTTP request header? — trojanfoe, Feb 28 '13 at 10:43
I've added that `postLength` line but I don't have anything for `Content-Type`. I didn't realise I needed to set that. — Robert, Feb 28 '13 at 10:46

score 2 · Accepted Answer · answered Feb 28 '13 at 10:49

2

I think the issue might be a missing Content-Type HTTP Request header field:

[request setValue:@"application/x-www-form-urlencoded; charset=UTF-8" forHTTPHeaderField:@"Content-Type"];

Also use UTF-8 to encode the payload:

NSData *postData = [post dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];

answered Feb 28 '13 at 10:49

trojanfoe

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OK, then time to turn to the server. Are you able to *mimic* your POST request using some other technology in order to verify that the problem doesn't lie within the server? – trojanfoe Feb 28 '13 at 10:55
I'm able to enter the individual parameters locally on the server, although not the whole POST request. – Robert Feb 28 '13 at 10:56
You need to mimic the POST request elsewhere in order to rule-out a server issue. You might be barking up the wrong tree. – trojanfoe Feb 28 '13 at 10:58
I created a webmethod that only takes in the entire `POST` as a parameter and it removes everything after an ampersand (&) so I think this may be where the problem lies, rather than parameter size. – Robert Feb 28 '13 at 12:15
I was indeed barking up the wrong tree. Some of the document titles contained ampersands. I wrote a little routine to change them to `and` on upload and that seems to have solved it. Thanks for your help. – Robert Mar 01 '13 at 11:33
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@Robert Another approach is to run all your parameters through `[NSString stringByAddingPercentEscapesUsingEncoding:]` before adding them to the payload. – trojanfoe Mar 01 '13 at 11:40

Max parameter size for NSData / setHTTPBody?

1 Answers1