Question

I currently have an ap that attempts to open a webview based on certain servers I am communicating with.

However, I allow the user the capability to type in their own server IPs in case both the iphone/ipad and server(or other device) are not on the same network. However, I am attempting to use NSURLConnection to detect if I can open a connection with the given IP however NSURLConnection never returns an error, even if the server address(or even a random web address) is completely bogus.

the .h

        @interface DetailViewController : UIViewController <UIPopoverControllerDelegate, UISplitViewControllerDelegate, UITableViewDataSource, UITableViewDelegate,UIWebViewDelegate, NSURLConnectionDataDelegate> {

the relevant code in the .m

   - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:
         (NSIndexPath *)indexPath
       {
        dev_ip = @"http://www.asdfasfdfa.com/";
        //dev_ip = (random ip)
        NSMutableURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:dev_ip]];

        NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
        if (conn) {
            NSLog(@"Connection established");    

        }
        else{
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:[NSString stringWithFormat:@"No Device at designated IP"]

                                                           delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
            [alert show];
        }
      }

this if/else always outputs ‘Connection established.’ Is this something NSURLConnection should not be used for? If so, what can I use to detect devices at given IP’s for connectivity. I need to stop the user from attempting to connect to bad IP’s so whats the best method in doing so?

Answer 1

NSURLConnection, when used with delegation, will call delegate methods when it connects, fails to connect and receive data. You should look into NSURLConnectionDelegate.

Here’s a quick example:

    // In your .h

    @interface MyClass : NSObject <NSURLConnectionDelegate, NSURLConnectionDataDelegate>

    @end

EDIT You actually need both delegates.

---

    // In your .m

    @implementation MyClass

    - (void)myMethodToConnect {

         NSString *dev_ip = @"http://74.125.137.101"; // Google.com

         NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:dev_ip]];

         NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    }

    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

        switch ([(NSHTTPURLResponse *)response statusCode]) { // Edited this!
            case 200: {
                NSLog(@"Received connection response!");
                break;
            }
            default: {
                NSLog(@"Something bad happened!");
                break;
            }
        }

    }

    - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
        NSLog(@"Error connecting. Error: %@", error);
    }
    @end

Also, just throwing it out there too, you don’t necessarily have to use an asynchronous call. You can send a synchronous call which doesn’t require you to implement a delegate. Here’s how:

    NSString *dev_ip = @"http://www.asdfasdfasdf.com/";
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:dev_ip]];
    NSURLResponse *response = nil;
    NSError *error = nil;

    NSData *connectionData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

You can check the response value and errors.