We're in the process of completing an application which is based on a licensing system. Users manage it through a web interface and can then sync their devices as they require. So once the device is sync'd the app is self sufficient to the point where the user needs to update their device with the latest set of data.
Now we have implemented the sync-process to verify if the user's license has expired or not before sync'ing. But the downside is that the updates aren't required that often and are more or less static over the period of our licenses.
As such, we're trying to figure out if it is possible on the device itself, to force the user to either sync up to our server at regular intervals or when the license is supposed to expire.
NSDate is an obvious no since its values are dependent on the user so can be changed easily. mach_absolute_time() was another option we considered but the timer changes when the iPad is restarted. We need some way to track absolute time since the license begun, regardless of whether the application or device were running or not and notify the user of this when the app starts.
Any help would be much appreciated.
Interesting problem. You could keep a NSUserDefaults value that represents the highest date that the app was run to detect if the user has changed the device clock. You could also build in a service client to go out and check an external server for the current time when the network is available. Doing this you're looking outside of the user's control to find the true time.
If the user is off the network you won't get a time, but with these devices they are on the network pretty often. You could also trigger the external time lookup when the device has a significant location change. That capability is described in the Apple documentation regarding multi-tasking options.
Related
I want to find iPhone devices/device tokens within a specific radius from particular location.
For example : Within a 25 K.M. of radius from Sydney,i want to get iPhone devices tokens.
I am working on ASP.NET MVC2 for this.
Let me know,if is there any API for that?
Thanks,
You are only able to get details for devices that you 'know' about. Your app will need to log unique IDs for each device, and your app will need to log known locations for devices. It's then up to you to look up, from your central database, the details of the devices within a certain distance. iPhones can update significant location changes when running in the background but it's up to you to track devices and accept the limitations that that data may not always be correct. eg. If a user falls outside connectivity then you will still have an old location logged for that user.
I'm not aware of a single API that offers this services, if you're coding it then in your app you will need to register devices identifiers and location information to a central server. You will also need to create the lookup to query your data to find devices within a location. I am guessing that you might want to send push notifications, in which case your app will also need to register for notification services too.
There is no way for you to discover devices that don't have your app running and you also do not know who the owner is.
In my application i want to run an internal clock in background mode [while application is not running in foreground].
The whole functionality will be like this:
The objective is to get the server time to use in the application, because using device time may sometimes cause issues. The issues may be in situations like somebody has changed the user's iPhone time etc. So i am following the below method.
-Running an internal clock in my application background even if the application is not running.
-Communicate with server every 15 minutes to get the real time and run a timer.
-If net is disconnected in between,timer will continue and take the timer time.
My application is heavily depended on this time factor as this is a ticket booking system.Kindly help me to implement this or please confirm whether this is possible or not?
I am developing an iPhone application which involves Ticket Booking System. I registered my application as location based beacuse it is using user's location taken in background for a purpose.
My problem is that i need to run an internal clock in my application in background mode. I need to write the codes for internal clock in core location delegate methods, so that internal clock will also run along with the location bsed services. Will my app get rejected? Is anything wrong in doing like this?
I need to get the correct time to use in my app, so that i am running this internal clock. I can use NSDate, but that will return the device time. Anyone can change the device time. So once somebody chaged, wrong time will affect the smooth functioning of the app. Kindly some body suggest to get the correct time with out running the internal clock ?
Update: Sorry to say my original answer isn't correct. When the device goes to sleep (can happen sometime after it's locked) the internal CPU clock stops ticking, and mach_absolute_time won't update either. Theoretically it will return the exact same value if you call it right before the device went to sleep, and after it awakes.
The best available way I know of to check for date changes is kern.boottime, it holds the boot time, and is modified whenever the system time changes. Among other things, kern.boottime will be updated if the user changes the time, or if the OS changes the time itself according to info from cell towers.
So, in your case, you can take the original time you calculated and modify it according to the modifications in kern.boottime. If you see kern.boottime changed significantly, it may mean that the device was turned off, and in this case you will need to contact the server to ask it for the time until the flight.
Relevant code:
time_t getBootTimeSecs(void)
{
struct timeval boottime;
size_t size = sizeof(boottime);
int ret = sysctlbyname("kern.boottime", &boottime, &size, NULL, 0);
assert(ret == 0);
return boottime.tv_sec;
}
Original (incorrect) answer: You can use mach_absolute_time which isn't affected by date changes made by the user.
When you book the ticket, get the correct date from the server and record mach_absolute_time. Now you will always be able to call mach_absolute_time whenever you want, calculate the difference from the one you recorded initially, and display the correct date.
This will only work as long as the device wasn't shut down, in that case it makes sense for the app to re-connect to the server to get the correct date.
You can also either Local or Push Notifications to alert the user when the target date is getting closer, even if the app isn't running.
apple is support small task for background mode which will work for approximate 10 sec only.
so you can do one thing when app is active then get time form server and update your local time according that.
I think that you can only detect that the date of the iOs device has been changed (using NSSystemClockDidChangeNotification).
I guess you to use this notification and force reload the real date of your application from your server (With a WebService).
EDIT: You can use the systemUptime in NSProcessInfo:
NSLog(#"ProcessInfo System uptime: %f",[NSProcessInfo processInfo].systemUptime);
but it will not solve your problem if the Device is restarted.
I think there are 2 ways you can go about solving your problem.
Never use system time. In other words, never call [NSDate date] in your code. When you need the current time, call an NTP server. This will of course cause latency in your app, but will guarantee accuracy.
When the app launches, or enters foreground, verify that the system time is reasonably accurate against an NTP server. If the system time is off by more than your tolerance level, then do not let them continue running the app until they address it. If the system time is okay, then start monitoring to ensure they don't change the system time while running the app (NSSystemClockDidChangeNotification). If they pass the initial check, but the move the clock forward, you can catch that and disable the app til they change it back to being accurate.
Here is an iOS NTP implementation which could be helpful in implementing either solution above. http://code.google.com/p/ios-ntp/
EDIT: The Ticketmaster app uses technique #2, so this seems like a reasonable solution for a ticketing app that requires your system time to be correct.
timezone settings should not affect time as in UTC
your app cannot run in the background. Abusing the location requirement for this will cause your app to be rejected by Apple
so my suggestion: do the logic server side with push notification
we are creating a location-enabled app where users use this app to record certain events in the field.
The important part of the event data is when an event happened. This is no issue when user is online, but we also support situations when user is offline (by remembering & later syncing events).
There could be situations when users are offline and they change the time on the phone, so that event times are wrongly recorded.
So, what would be the best way to ensure we get a correct time, independent of user actions, given that device could be offline. Some ideas:
GPS time. Is it possible to acquire it?
Tracking system time changes made by user?
Any other idea?
Note: time does need second accuracy, approximately minute accuracy would be ok.
Note2: we are creating mobile apps for Android and iPhone, so I'm interested for generic solutions and also solutions that are specific to any of those two platforms.
I, personally, wouldn't worry so much about this scenario. The liklihood of someone intentionally changing the time on their Android (which periodically throughout the day syncs to a time server automatically) while offline seems low to me. That being said, the only way I could see compensating for this is to keep a service running in the background that keeps a running tally of the seconds passed since recording the location data offline. Once uploaded to your servers you could use the elapsed seconds to calculate a time offset from current UTC time. It's an awful lot to go through, but it would work.
GPS time is an interesting idea, but Android allows users of the SDK to send mock locations to their devices. I'm not sure you could reliably track changes to system time either, and even if you could you'd be capturing them after the fact without the current real time as context.
We use GPS times in our app for very similar reasons. Since our users are in different time zones and we want local times, we define from our server what time zone they are in at installation time (they don't move very far). Hadn't thought of the mock GPS locations, but you would need to be a fairly advanced user to do that.
I have an app that requires me to take an action after some period of time. For example, if an user hasn't been inside the app in few weeks, when the user eventually starts the app, I have to ask them to put in a special code that was given to them when they installed this app. (this is an in-house app and i am being required to do this due to security concerns)
I am using the [NSDate date] method to retrieve the date when the user logs in and save it into a database. I compare this saved date next time they open up the app and see how long its been since their last login. The problem is that [NSDate date] gives the time that is effected by the time settings that can be changed manually by the user in the native settings app. As you can probably tell, this causes lots of problems to my situation. If the user is suppose to be put the special code after 3 weeks of inactivity, he can cause the app to show this screen by modifying the time in the native settings app or worse, get away from it by setting the time to a previous date that will be within 3 weeks of his activity.
Is there a way to get the "system time" instead of the "user time"? I have looked into mach_absolute_time() but this gets reset after restart of the device. Since the time of inactivity I will be comparing against is pretty large, chances are device would have been restarted by then. I also thought of using network connection to get the time from servers outside the app, but lots of users won't have access to wifi where they use their iPads. That will be my last resort solution if i can't find anything else. Because of their location during usage, I am trying to use everything on the device itself.
Am I overlooking something simple here? this seems too simple of a problem to not have an answer. Please guide me toward the right direction. Thank you in advance.
Why not query a remote server for the time - lots of NTP servers about or just make a simple HTTP request to a php script on your own server. Of course if your app is likely never to be connected to the internet that could be a problem, but once you have a 3rd party time its quite easy to guess if the user has been playing with the clock.
If this is an inhouse app (so you aren't constrained by Apples approval process), you could mark your app as doing some background stuff (voip or receiving location updates), so that the app will always be active and you'd be able to update some sort of an "unused" counter. Voip app will even be restarted by the OS after device reboot.
But of course it'll drain the battery somewhat.
Either: make having the actual time an essential feature of your app. This way the users will have a need to keep the time of the device current and can't go back three weeks
Or: mark the code as expired and save this information before the app informs the user. This will stop most user from setting the time back. Most will try once or twice, see that the app stays disabled and will give up.
You can also save the timestamp of the last successful execution and if that is more than a reasonable time frame in the future (remember summer/winter time) then consider it a "hack attempt". Put a CRC check (or whatever obscure idea you come up with) on that timestamp and save it too and you will stop a large number of script kiddies.
You can never stop the diehard hacker who search actively for every trick you might have put into the app. Just focus on the "average" user.
I have a requirement in my iPhone app that I know when somebody running the same app is close by.
I'm thinking that GameKit using Bluetooth would let me do that. GPS location is not precise enough in this particular case.
However, if the user closes the app then the function won't work anymore. Even under iOS4, the task switching will close down the BonJour services so I can't have the app run in the background.
Seems to me I can only have this function if the user leaves the app up and running. Would you agree? Or is there a different approach I can take?
People are very concerned with privacy, so they would naturally expect such privacy invading functionality to be switched off when they close down the application.
If they choose to have this feature enabled, then it's a different matter. Then they expect that somebody else may locate them.
You might however consider implementing some sort of opt-in offline service, where the latest gps position is stored on a server including a timestamp. When somebody else (with the app running) moves within a certain distance of this location while it's still "fresh", then you send off a notification to the first device. That way the user would be notified that somebody may be close, and can then switch on their own device.