how to solve this error ?

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Xcode

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.responseData = [NSMutableData data];
    //NSURLRequest *request = [NSURLRequest requestWithURL:
                            //// [NSURL URLWithString:@"https://maps.googleapis.com/maps/api/place/search/json?location=-33.8670522,151.1957362&radius=500&types=food&name=harbour&sensor=//false&key=AIzaSyAbgGH36jnyow0MbJNP4g6INkMXqgKFfHk"]];
    //NSURLRequest *request = [NSURLRequest requestWithURL:
    //[NSURL URLWithString:@"http://162.242.142.88/CarShareService/CarShareService.svc/Login?UserName=alex@rentcentric.com&Password=12345"]];
    NSString * key = [NSString stringWithFormat:@"UserName=%@&Password=",@"alex@rentcentric.com" ,@"12345" ];
    NSURL * url = [NSURL URLWithString:@"http://162.242.142.88/CarShareService/CarShareService.svc/Login"];
    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];
    [request setHTTPMethod:@"GET"];
    [request setHTTPBody:[key dataUsingEncoding:NSUTF8StringEncoding]];
    [[NSURLConnection alloc] initWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    NSLog(@"didReceiveResponse");
    [self.responseData setLength:0];

}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [self.responseData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    NSLog(@"didFailWithError");

    NSLog([NSString stringWithFormat:@"Connection failed: %@", [error description]]);
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"connectionDidFinishLoading");
    NSLog(@"Succeeded! Received %d bytes of data",[self.responseData length]);
    // convert to JSON

    NSError *myError = nil;







    NSDictionary *res = [NSJSONSerialization JSONObjectWithData:self.responseData options:NSJSONReadingMutableLeaves error:&myError];

    //[self setResponseSerializer:responseData];
    NSDictionary *posts = [res objectForKey:@"StatusInfo.StatusCode"];
    if(res == nil){
        NSLog(@"JSON Error: %@", myError);
        return;
    }else{

         NSLog(@"JSON Error%@",myError);
    }

the error is
Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x8d6ca50 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}