Checking for valid IP for connection with NSURLConnection - iphone

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.

Answer 2

There's a better way to test whether a server is valid or not. The Reachability class provides good API for this purpose.