Upload files (images, pdf) with parameters to the server - ios

Question

I would like to upload 1pdf file and array of images.
I can upload 1pdf and 2jpg files, if jpg files more than two I get message: Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (No value.) UserInfo=0x174268000 {NSDebugDescription=No value.}
Why is this happening? Also I tested server with POSTMAN and it work well.
NSURL *URL = [NSURL URLWithString:constFileUploadURL];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
[request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
[request setHTTPShouldHandleCookies:NO];
[request setTimeoutInterval:60];
[request setHTTPMethod:#"POST"];
NSString *boundary = #"0xLhTaLbOkNdArZ";
NSString *contentType = [NSString stringWithFormat:#"multipart/form-data; boundary=%#", boundary];
[request addValue:contentType forHTTPHeaderField:#"Content-Type"];
NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"user_id\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
NSString *userid = [NSString stringWithFormat:#"%li",userID];
[body appendData:[userid dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithString:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"key\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[constBackendKey dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithString:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
for (NSData *data in arrayWithFiles)
{
NSString *fileName;
if ([arrayWithFiles indexOfObject:data] == 0)
{
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
fileName = #"Content-Disposition: form-data; name=\"files\"; filename=\"PdfFile.pdf\"\r\n";
[body appendData:[fileName dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithString:#"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:data]];
[body appendData:[[NSString stringWithString:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}
else
{
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"files%ld\"; filename=\"image%ld.jpg\"\r\n",[arrayWithFiles indexOfObject:data],[arrayWithFiles indexOfObject:data]] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithString:#"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:data]];
[body appendData:[[NSString stringWithString:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}
}
[body appendData:[[NSString stringWithFormat:#"--%#--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[request setHTTPBody:body];
_connection = [NSURLConnection connectionWithRequest:request delegate:self];

Answer 1

Cod works, problem was on server side. File uploading 50mb, a post size 8mb.