How to write a simple Ping method in Cocoa/Objective-C

Question

I need to write a simple ping method in Cocoa/Objective-C. It also needs to work on the iPhone.

I found an example that uses icmp, will this work on the iPhone?

I'm leaning towards a solution using NSNetServices, is this a good idea?

The method only needs to ping a few times and return the average and -1 if the host is down or unreachable.

Gene Myers · Answer 1 · 2021-04-10T23:38:42.130

NOTE- I would recommend Chris' solution below which actually answers the question asked, directly. This post from 12 years ago was in response to the original authors upvoted answer, to which I had a better solution. As the author upvoted the answer above that used Reachability, I assumed that he was in fact more interested in reachability than actually in sending a ping, hence my answer. Please consider this before downvoting this answer.

StreamSCNetworkCheckReachabilityByName is deprecated and NOT available for the iPhone. Note: SystemConfiguration.framework is required

bool success = false;
const char *host_name = [@"stackoverflow.com" 
                         cStringUsingEncoding:NSASCIIStringEncoding];

SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL,
                                                                        host_name);
SCNetworkReachabilityFlags flags;
success = SCNetworkReachabilityGetFlags(reachability, &flags);

//prevents memory leak per Carlos Guzman's comment
CFRelease(reachability);

bool isAvailable = success && (flags & kSCNetworkFlagsReachable) && 
                             !(flags & kSCNetworkFlagsConnectionRequired);
if (isAvailable) {
    NSLog(@"Host is reachable: %d", flags);
}else{
    NSLog(@"Host is unreachable");
}

Hi. Excelent code and helpful, but only one thing. You require add the code `CFRelease(reachability)` after call `SCNetworkReachabilityGetFlags` to release reachability variable (to prevent memory leaks) as is mentioned in [documentation](https://developer.apple.com/reference/systemconfiguration/1514904-scnetworkreachabilitycreatewithn?language=objc) — Carlos Guzman, Oct 23 '16 at 14:47
`SCNetworkReachabilityGetFlags` is a poor substitute of ping – if the device is connected to a network, `kSCNetworkFlagsReachable` will be set and `kSCNetworkFlagsConnectionRequired` will be unset even though the target host is offline. — adib, Feb 14 '17 at 13:45
I was improving on the accepted answer. I don't debate that SCNetworkReachabilityGetFlags is a poor substitute for 'ping', but if you are just trying to determine reachability, as was rjstelling objective, then this is a fine solution. If you need to monitor latency or provide a heartbeat, then a 'ping' solution is arguably better. — Gene Myers, Feb 14 '17 at 13:51

score 32 · Answer 2 · answered Jan 27 '12 at 05:44

32

I had this same problem, and ended up writing a simple wrapper around SimplePing to achieve this, wrote a blog about it and there's some code on github, hopefully will help someone here:

http://splinter.com.au/how-to-ping-a-server-in-objective-c-iphone

answered Jan 27 '12 at 05:44

Chris

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Upvote for a solution that actually answers the question (vs all this useless Reachability stuff which people seem to like but which is totally not addressing the question asked!). Thank you! – Bill Patterson Mar 22 '13 at 04:51
Yes, this is the actual answer. – user623396 Nov 10 '14 at 13:39

score 13 · Answer 3 · answered Nov 08 '09 at 22:16

You are not missing anything -- "Reachability" doesn't actually test that the target domain is in fact reachable, it only assesses if there is a pathway out of the machine by which the target domain is potentially reachable. So long as you have some outbound connection (e.g., an active wirless or wired connection), and a routing configuration that leads to the target, then the site is "reachable" as far as SCNetworkReachability is concerned.

score 5 · Answer 4 · answered Apr 26 '10 at 19:56

5

Pinging on the iPhone works a bit different than on other platforms, due to the fact that you don't have root access. See this sample code from Apple.

answered Apr 26 '10 at 19:56

Monobono

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This file is removed from all around apple developer library. – ahmet alp balkan Aug 03 '12 at 16:34

score 0 · Answer 5 · edited May 23 '17 at 11:53

The answer Gene Myers posted works using "SCNetworkReachabilityCreateWithName" for me - but only in the simulator. On my device (iPod w/OS 2.2.1) it always returns "Host is reachable" even for nonsense addresses like "zzz".

Am I misunderstanding something? Thanks.

Here's my code just in case:

From How to write a simple Ping method in Cocoa/Objective-C

    - (IBAction) TestReachability:(id)sender
{
    bool success = false;
    const char *host_name = [ipAddressText.textcStringUsingEncoding:NSASCIIStringEncoding];
    NSString *imageConnectionSuccess = @"Connected.png";
    NSString *imageConnectionFailed = @"NotConnected.png";

    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL,
                                                                                host_name);
    SCNetworkReachabilityFlags flags;
    success = SCNetworkReachabilityGetFlags(reachability, &flags);
    bool isAvailable = success && (flags & kSCNetworkFlagsReachable) && 
        !(flags & kSCNetworkFlagsConnectionRequired);
    if (isAvailable)
    {
        NSLog([NSString stringWithFormat: @"'%s' is reachable, flags: %x", host_name, flags]);
        [imageView setImage: [UIImage imageNamed:imageConnectionSuccess]]; 
    }
    else
    {
        NSLog([NSString stringWithFormat: @"'%s' is not reachable", host_name]);
        [imageView setImage: [UIImage imageNamed:imageConnectionFailed]]; 
    }
}

score -1 · Answer 6 · answered Oct 19 '09 at 14:25

Please take note that there is an difference between the simulator and the actual iPhone. The simulator is not a true simulator like the one supplied by Android, it uses Mac OSX classes for most of the functions.

This is particularly hell if there is a difference between the Mac OSX and iPhonew(for example the keychain).

Vadim · Accepted Answer · 2009-06-17T01:02:14.667

-8

The code below seems to be working synchronously:

const char *hostName = [@"stackoverflow.com"
                        cStringUsingEncoding:NSASCIIStringEncoding];
SCNetworkConnectionFlags flags = 0;
if (SCNetworkCheckReachabilityByName(hostName, &flags) && flags > 0) {
  NSLog(@"Host is reachable: %d", flags);
}
else {
  NSLog(@"Host is unreachable");
}

Note: SystemConfiguration.framework is required

edited Jun 17 '09 at 01:02

answered Jun 16 '09 at 23:07

Vadim

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Unfortunately, SCNetworkCheckReachabilityByName is now deprecated. – William Remacle Oct 12 '10 at 10:30
30

8 votes and +bounty for code that totally doesn't do what question was about, i.e. ping/traceroute but it's a DNS lookup, basically. – bestsss Oct 26 '11 at 08:10
The code is not only deprecated but also looking up the DNS – Adro Aug 06 '15 at 06:45
1

“You cannot delete this accepted answer”. Sorry guys! – Vadim Aug 11 '15 at 13:33
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`SCNetworkReachability` is a poor indicator of whether a host is online. On a LAN situation, reachability seems to always returns that the host is reachable whenever there is a WiFi connection although it's really an invalid host name. – adib Feb 14 '17 at 12:29

How to write a simple Ping method in Cocoa/Objective-C

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