iOS connectionDidFinishLoading doesn't trigger

#import <Foundation/Foundation.h>
#import "Reachability.h"
//implementar protocolo
@protocol RedDelegate <NSObject>

-(void) terminaDescarga:(NSData*)datos
                  conId:(NSInteger)id
                    httpCodeReturn:(int)code
httpStringCodereturn:(NSString*)codestring;


-(void) errorEnDescarga:(NSInteger)codigo descrip:(NSString *)descError conId:(NSInteger)id;

@end

@interface JFRed : NSObject <NSURLConnectionDataDelegate> @property(nonatomic,strong) NSObject<RedDelegate> *delegado;
@property (nonatomic,strong) NSMutableData *datosDescargados;
@property (nonatomic,strong) NSURLConnection @property(nonatomic) NSInteger id;
@property(nonatomic) int httpCodeReturn;
@property(nonatomic) NSString *httpStringCodereturn;

-(void) descargar:(NSString*)direccion conId:(NSInteger)id;
-(void) jsonPostRequest:(NSString *)direccion tipoId:(NSInteger)id postData:(NSString*) postData;
-(void) comprobarRed:(NSString*)direccion;
-(NSDictionary*) connectToWSArticulo:(NSString *) lstrIdArticulo;

@end

#import "JFRed.h"

@implementation JFRed


-(void) descargar:(NSString*)direccion conId:(NSInteger)id
{
    self.id = id; //es el número de tarea que se esta bajando
    NSString *dir = direccion;
    NSURL *url = [NSURL URLWithString:dir];
    NSMutableURLRequest *solicitud = [NSURLRequest requestWithURL:url];
    //inicia la descarga asincrona
    self.conexion = [[NSURLConnection alloc] initWithRequest:solicitud delegate:self];

    if(self.conexion!=nil)
    {
        self.datosDescargados = [NSMutableData data];//inicializa
    }
    
}


-(void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse* httpReturn = (NSHTTPURLResponse*)response;
    self.httpCodeReturn = [httpReturn statusCode];
    self.httpStringCodereturn = [NSHTTPURLResponse localizedStringForStatusCode:self.httpCodeReturn];
    
    self.datosDescargados.length = 0;
}


-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.datosDescargados appendData:data];
}

-(void) connectionDidFinishLoading:(NSURLConnection *)connection
{
        [self.delegado terminaDescarga:self.datosDescargados conId:self.id httpCodeReturn:self.httpCodeReturn httpStringCodereturn:self.httpStringCodereturn];
}


-(void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [self.delegado errorEnDescarga:error.code descrip:[error.userInfo objectForKey:NSLocalizedDescriptionKey ] conId:self.id];   
}



#pragma mark - connectToWSArticulo
-(NSDictionary*) connectToWSArticulo:(NSString *) lstrIdArticulo //antes regrasab un nsmutabala array
{
    NSString *lsStr = @"http://";
    //NSString *lsStr2 = @"/WS_Articulo/ws/ArticulosValorWS/consultaExiInvb?articulo="; Pasada
    NSString *lsStr2 = @"/WS_Cliente/ws/rest/datosArticuloWS/getDatosArticulo?articulo=";
    //Obtengo la dirección IP a realizar la conexión
    //NSString *lstrIp = [self getSettings:@"direccionIP"]; Si es que la IP se encontrara en Settings de la aplicación
    //NSString *lstrIp = @"192.168.1.52:8181"; IP de la intranet(ya no se deberá de usuar)
    NSString *lstrIp = @"189.210.175.215:8085";
    //Concatena variables
    NSString *lsCadena = [NSString stringWithFormat: @"%@%@%@%@",lsStr,lstrIp,lsStr2,lstrIdArticulo];
    NSData *data = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:lsCadena]];
    //NSArray *dictionaryArray = [self convertJsonDataDiccionary:data];// Antes regresaba un array
    NSDictionary *diccionario = [self convertJsonDataDiccionary:data];
    return diccionario;
}


-(NSDictionary *)convertJsonDataDiccionary:(NSData*)data //antes regresaba un nsarray
{
    NSError *error = nil;
    NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    if (error) {
        UIAlertView *alerta = [[UIAlertView alloc] initWithTitle:@"AVISO" message:@"No se puede conectar al servicio, intente de nuevo más tarde, gracias"  delegate: nil cancelButtonTitle:@"Aceptar" otherButtonTitles:nil];
        [alerta show];    }
    //NSArray *array = [dictionary objectForKey:@"ecomExist"]; Aqui convertia el diccionario a array
    return dictionary;
}

@end

JFRed *red = [[JFRed alloc]init];
    red.delegado = self;
    [red descargar:[self.diccioPrincipal valueForKey:@"imgArt"] conId:1];