Convert a JSON NSData to NSDictionary

I'm using an API service of a web service and it is written in their description that they send JSON data wich also matches in my opinion with the response I get from it. Here a part of it which I got from the NSURLConnection-Delegate (connection didReceiveData: (NSData *) data) and converted in a NSString using:

NSLog(@"response: %@", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

Here the snippet:

{"scans": 
{
    "Engine1“: 
    {
        "detected": false, 
        "version": "1.3.0.4959", 
        "result": null, 
        "update": "20140521"
    }, 
    "Engine2“: 
    {
        "detected": false,
         "version": "12.0.250.0",
         "result": null,
         "update": "20140521"
    }, 
        ...
    },
    "Engine13": 
    {
         "detected": false,
         "version": "9.178.12155",
         "result":

In the NSLog-String it stops there. Now I would like to know from you whats wrong that I can't convert this data to a JSON Dictionary with this lines of code:

NSError* error;
    NSMutableDictionary *dJSON = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];

I experiment with some options but always the same error:

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" 
(Unexpected end of file while parsing object.) UserInfo=0x109260850 {NSDebugDescription=Unexpected end of file while parsing object.}

Everything indicates that the JSON packet is incomplete but I don't know how to check it or how to look for the issue which should be located in my code.

Did you implemented all the delegate methods of NSURLConnectionDelagate.It looks like you are taking the data for conversion from "- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data" delagate method. If so you may get incomplete data and that can not be converted.

Try this:

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    // A response has been received, this is where we initialize the instance var you created
    // so that we can append data to it in the didReceiveData method
    // Furthermore, this method is called each time there is a redirect so reinitializing it
    // also serves to clear it
    lookServerResponseData = [[NSMutableData alloc] init];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // Append the new data to the instance variable you declared
    [lookServerResponseData appendData:data];
}


- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // The request is complete and data has been received
    // You can parse the stuff in your instance variable now
    NSError *errorJson=nil;
    NSDictionary* responseDict = [NSJSONSerialization JSONObjectWithData:lookServerResponseData options:kNilOptions error:&errorJson];

     NSLog(@"responseDict=%@",responseDict);

    [lookServerResponseData release];
    lookServerResponseData = nil;
}

Here, lookServerResponseData is instance of NSMutableData declared globally.

Hope it will help.