Is it advisable to use Reachability to check the availability of a remote host?

Question

How reasonable is it to use the Reachability class (from Apple) to check the availability of a remote host? e.g. www.google.com

or should i use

NSString *connectedString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://www.google.com/"]]; 

if ([connectedString length] != 0) // Host Available

What is the best option since I heard Reachability has a bug with checking host availability ?

Answer 1

Here is a good way to check if the host is accessible:

    NSURLResponse *response=nil;
    NSError *error=nil;
    NSData *data = nil;
    NSURLRequest *request = [NSURLRequest requestWithURL:your_url];

    data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

If the host is offline, you will receive an error code in error, nilin, dataand nilin the responsevariables.
If the host is online and responding, there will be several response, dataand error==nil.

Answer 2

, . , . , , Wi-Fi. "" .

Answer 3

, , . , .

ReachabilityManager, Reachability, URLConnection, , . , Reachability ( Tony Million, , Apple).

/ , , ( ) /. , .

, , , . -.

, singleton, , . AppDelegate.

, , / , , .

UnitTests, , .

NSObject :

.h

#import <Foundation/Foundation.h>
@interface ReachabilityManager : NSObject

+ (void)startReachabilityWithHost : (NSURL *)hostName;

@end

.m

#import "ReachabilityManager.h"
#import "Reachability.h"

@implementation ReachabilityManager

static ReachabilityManager *_sharedReachabilityManager;
static Reachability *reachability;
static NSURL *_hostName;
static BOOL isServerReachable;
+ (void)initialize
{
    static BOOL initialized = NO;
    if(!initialized)
    {
        initialized = YES;
        _sharedReachabilityManager = [[ReachabilityManager alloc] init];
    }
}

+ (void)startReachabilityWithHost : (NSURL *)hostName{
    _hostName = hostName;

    reachability = [Reachability reachabilityWithHostname:hostName.host];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(reachabilityChanged:)
                                                 name:kReachabilityChangedNotification
                                               object:nil];
    [reachability startNotifier];
}

+ (void)stopReachability{
    [reachability stopNotifier];
    [[NSNotificationCenter defaultCenter]removeObserver:kReachabilityChangedNotification];
}

+(void)reachabilityChanged: (NSNotification *)notification{
    dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        BOOL isServerCurrentlyReachable = NO;
        do{
            isServerCurrentlyReachable = [self checkConnectivityToServer];
            BOOL wasServerPreviouslyReachable = isServerReachable;
            isServerReachable = isServerCurrentlyReachable;

            if (NO == wasServerPreviouslyReachable && YES == isServerCurrentlyReachable)
            {
                NSLog(@"REACHABLE!");
                [[NSNotificationCenter defaultCenter]postNotificationName:@"kNetworkReachabilityCustom" object:[NSNumber numberWithBool:YES]];
            }
            else if (YES == wasServerPreviouslyReachable && NO == isServerCurrentlyReachable)
            {
                NSLog(@"UNREACHABLE!");
                [[NSNotificationCenter defaultCenter]postNotificationName:@"kNetworkReachabilityCustom" object:[NSNumber numberWithBool:NO]];
            }
            [NSThread sleepForTimeInterval:5.0];
        }while(!isServerCurrentlyReachable);
    });

}


+(BOOL)checkConnectivityToServer{
    NSURLResponse *response;
    NSError *error=nil;
    NSData *data = nil;
    NSURLRequest *request = [NSURLRequest requestWithURL:_hostName];

    data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

    return (data && response);

}


@end

Answer 4

, - , Reachability. .

Answer 5

, Reachability. http://www.raddonline.com/blogs/geek-journal/iphone-sdk-testing-network-reachability/

NSString *connectedString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://www.google.com/"]]; 

if ([connectedString length] != 0) // Host Available

, , , . .

Answer 6

developer.apple.com .

// Create the request.

NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.apple.com/"]

                        cachePolicy:NSURLRequestUseProtocolCachePolicy

                    timeoutInterval:60.0];

// create the connection with the request

// and start loading the data

NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

if (theConnection) {

    // Create the NSMutableData to hold the received data.

    // receivedData is an instance variable declared elsewhere.

    receivedData = [[NSMutableData data] retain];

} else {

    // Inform the user that the connection failed.

}