ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
{
    dispatch_semaphore_t sem;
    NSMutableData *alldata;
}

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    sem = dispatch_semaphore_create(0);
    alldata = [[NSMutableData alloc] init];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

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

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    dispatch_semaphore_signal(sem);
}

- (IBAction)clicked:(id)sender {
    //run clickThread function in a separate thread
    [self performSelectorInBackground:@selector(clickThread) withObject:nil];
}

- (void) makeconnection:(NSString*)url {
    NSURLRequest *request = [NSURLRequest requestWithURL: [NSURL URLWithString:url]];
    [NSURLConnection connectionWithRequest:request delegate:self];
}

- (void) clickThread {
    NSLog(@"making connection with google");
    //NSURLConnection will only work if it is run on the main thread
    [self performSelectorOnMainThread:@selector(makeconnection:) withObject:@"http://www.google.com" waitUntilDone:NO];
    
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"google done");
    NSLog(@"%@", [[NSString alloc] initWithData:alldata encoding:NSUTF8StringEncoding]);
    
    NSLog(@"making connection with yahoo");
    sem = dispatch_semaphore_create(0);
    alldata = [[NSMutableData alloc] init];
    [self performSelectorOnMainThread:@selector(makeconnection:) withObject:@"http://www.yahoo.com" waitUntilDone:NO];
    
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"yahoo done");
    NSLog(@"%@", [[NSString alloc] initWithData:alldata encoding:NSUTF8StringEncoding]);
}
@end