iOS How can I get the content of an URL without having memory leaks?

#import "TestConnectionAppDelegate.h"

@implementation TestConnectionAppDelegate

@synthesize window;
@synthesize responseData=_responseData;

- (void)applicationDidFinishLaunching:(UIApplication *)application {    
    [window makeKeyAndVisible];
	
	NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.puzzlemaniak.com"]];
    
    
    [NSURLConnection connectionWithRequest:req delegate:self];
}


- (void)dealloc {
    [window release];
    [super dealloc];
}


- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    
    if (!_responseData) {
        [self setResponseData:[NSMutableData data]];
    }
    
    [_responseData appendData:data];
}


- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)URLresponse {
    
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)URLresponse;
    
    if (![httpResponse isKindOfClass:[NSHTTPURLResponse class]]) {
        NSLog(@"Unknown response type: %@", URLresponse);
        return;
    }
    
    _responseStatusCode = [httpResponse statusCode];
    
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection {
    
    
	NSString* res=[[[NSString alloc] initWithData:_responseData encoding:NSUTF8StringEncoding] autorelease];
	NSLog(@"res:%@",res); 
}


@end

#import <UIKit/UIKit.h>

@interface TestConnectionAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
	NSURLConnection *_connection;
    NSMutableData *_responseData;
    NSMutableString *_xmlChars;
	
    NSInteger _responseStatusCode;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (retain) NSMutableData *responseData;