Trying To Send Multipart/Form Data in Objective-C, To µTorrent's Web API

Question

I've been trying to get this code working to send a torrent's data to the µTorrent Web API, unfortunately, as far as I can tell, nobody has ever tried to make a .torrent file handler for µTorrent in Objective-C before, which isn't all that surprising.

I have this code here at the moment, but I invariably get the error message: "Error: torrent file content not supplied in form parameter".

NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@?token=%@&action=add-file", [self getBaseURL], token]]];
NSString * boundary = @"!@!@!@!@!@!@!@!@!";
NSMutableData * body = [NSMutableData alloc];
NSData * torrentFileContents = [[NSFileManager defaultManager] contentsAtPath:fileName];

[request setHTTPMethod:@"POST"];
[request setValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary] forHTTPHeaderField:@"Content-Type"];
[request setValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary] forHTTPHeaderField:@"enctype"];

[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", @"application/x-bittorrent"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"torrent_file\"; filename=\"%@\"\r\n", fileName] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Length: %ld\r\n", [torrentFileContents length]] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:torrentFileContents]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];


[request setHTTPBody:body];

Answer 1

I found an example of what I wanted to do, written in JS, I was able to make it work by tweaking the code to look like this.

NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@?token=%@&action=add-file", [self getBaseURL], token]]];
NSString * boundary = [NSString stringWithFormat:@"AJAX-----------------------%f", [[[NSDate alloc] init] timeIntervalSince1970]];
NSMutableData * body = [NSMutableData alloc];
NSData * torrentFileContents = [[NSFileManager defaultManager] contentsAtPath:fileName];

[request setHTTPMethod:@"POST"];
[request addValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary] forHTTPHeaderField:@"Content-Type"];

[body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"torrent_file\"; filename=\"%@\"\r\n", fileName] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", @"application/x-bittorrent"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:torrentFileContents]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

[request setHTTPBody:body];

return request;

Answer 2

Why are you putting the content type and length in the request body? Did you try using setValue to add the necessary HTTP headers like Content-Type?

for example:

[request addValue:@"text/xml;charset=utf-8" forHTTPHeaderField:@"Content-Type"];