hi i am making an app in which user sends xml to server and get response....
now i have to save the date and time of sending and response of that request....for this should i use iphone's date or check it online?
because my thinking is that the iphone's date and time may not be correct.....always...so it is better to check the time online ....
i know the local part but need help regarding online check....please help
Just use the local time. It will save you a lot of trouble and work. Or is your app so absolutely dependent on the correct time, like to display the current position of the sun or something ? If not, the local time is likely "good enough".
If you need the same time as the server, then it would seem that you need to establish the offset between server time and local time, and then you can adjust your local timestamp.
Is there a way to get the (current) time from the server?
Assuming the timestamp you're saving is for the request sent from the iphone and the response received by the iphone, then it would actually seem logical to use local (iphone) time.
You could always use NTP (http://en.wikipedia.org/wiki/Network_Time_Protocol) to get the current time, but that doesn't guarantee the time is thesame as the server.
You usually don't need absolute time of some sort, just the same time source as your server and your server's database.
So compare your local time with whatever the server thinks the time is and adjust accordingly.
Related
Can Firebase get accurate time for offline records which have been stored in device when the device's clock has been changed? The device's clock might be changed when the user rebooted the device or when the user adjusts the date time manually.
My case is quite similar to Get actual DateTime of a device in Offline Mode which I can quote here 1) The application can work in online as well as offline. The app has a feature to create and save the NOTES inside the application. Also, When the app gets internet connection, I need to send the NOTES to backend server. I have a field called 'DATECREATED' in each NOTE (the datetime where the actual NOTE was created) ISSUE: If the User has set the DateTime wrongly in the device, My application sends the incorrect DATETIME to server.
I am going to handle the offline issue on Android and IOS platform, so I came out with another possible solution such as get the GPS time, using some sort of background counter, etc. Based on my experiment, the solution are not reliable enough and some might difficult to do. That's why I decided to get the accurate timestamp using Firebase.
I read a reference https://firebase.google.com/docs/database/flutter/offline-capabilities#clock_skew, but I am not quite sure whether it can help me to get accurate time for offline records.
There is no way you can get a server timestamp while offline. Why? Simply because the timestamp is totally generated on the server. And since you're offline and cannot communicate with the server, you cannot get an estimation. So there is no other system that can generate a timestamp other than the Firebase server.
Besides that, a date that can be generated on the client can be manipulated, so you cannot rely on that.
The option that you have in my opinion would be to have two fields. One is for the real timestamp, which you'll be received when you're back online and the other one is what the client provides. In that way, you make a comparison, if this is what you want.
Edit:
Firestore, is a Cloud hosted NoSQL database. So there is no way you can generate an accurate time while the user is offline. What you can certainly do is calculate the period of time while the user is offline. This means that you have to calculate the number of minutes the user has lost connectivity. Let's say a user losses connectivity for 10 minutes, when it regains connectivity, you receive the Firestore timestamp. Now, all you have to do is to subtract those 10 minutes from the received timestamp in order to have the accurate time that you're looking for.
In my Delphi Windows application i need to login every day.
at first i used system date (11-11-2019) and i compare system date to stored one every time on OnCreate if date is different i call login.
But the system time can be paused right ? Then i thought of server time but checking server time on every OnCreate is not efficient i think as my app launches many times.
Can't use token based system to check as i am using firebase REST-API backed and it's token is expired in every one hour however if i use token based i still need to compare it and the system time might be paused.
How to effectively check if date is changed ?
The inapp time is short as the work is done in 10 seconds and the form may be then closed by user and the next app start time may be less a minute so why call for the server time again ?
You can check the current date and time querying a NTP server.
See this answer for more details.
I am developing an application that must work online and also offline. This application should sync informations with our server. For this, we need that the device utilize the server clock.
I found a lot of information, and I get the following idea:
When the user logins online I will force him to get the server clock time. In this moment he obrigatory must have internet connection, so it is ok.
When I get the clock server time, I get the systemUptime information that says the interval that the device is turned on, and I store it. I can get systemUptime like this:
[NSProcessInfo processInfo].systemUptime
When the user to create a new local file, I will know the current interval based on systemUptime function, so I know the current time, and I don't depend the iOS system clock.
The problem is: Everytime that device is rebooted, or turned off, the systemUptime is reseted. Until here OK, I can solve it forcing the user to login again, and getting the server clock time again. My problem is to know when the device was rebooted. Can you help me? Thank you guys!
My advice would be to not refer to the device time at all. Get the the files from the server and have the server also answer the server time that the files are retrieved. You can store this in the file, in the file name, or separately on the device.
At some point in the future ask the server if there's a file newer than the server time you recorded earlier.
In this sense, the time isn't really a time at all, it's a version number, and you could make that explicit with the server too, using just an integer from the server that indicates progressing sequence of versions.
If it's important that your app be strong in this way, your only choice is to remain independent of device time. Otherwise, there are too many ways it can break (including small time errors due to latency on the time check, or device factory resets or malicious actions by a user). It's better to remain independent of device time if you can.
When you get the systemUptime the first time, subtract it from the current (iOS) date and time. That's the time the system was last brought up.
Then recalculate this value whenever necessary. If the "time the system was last brought up" has changed, then you know it's time to log in again.
However, as suggested by another commenter, I suspect there's a better way to tackle this from scratch.
For various reasons I need to get from the iPhone the current date and time that can't be meddled with by the user. Yes, I've seen how one can check a server (e.g., here), but that's not invulnerable to tampering if you take a moment to reflect.
There are two knee-jerk reactions I'm expecting to hear:
Use the GPS time.
It can't be done.
In answer to another question, I've described my researches into this matter. To summarize them:
The GPS time shifts with the user-defined settings.
The iPhone definitely has an internal tamper-proof time and date, as shown when date-time reverts after Set Automatically in Settings > General > Time & Date is turned back to on even in a fallout shelter.
What I want to know is how to access this tamper-proof time.
Edit
Just to be clear, the server-based solution is not suitable. For one, it could be faked. For another, the app needs to work without a network connection.
Assuming you always have Internet available, you could implement a class or object that connects to a remote Network Time Protocol server.
Here's an open source GitHub project that should get you started, and the related StackOverflow question I found it at.
This is the scenario:
I'm writing a medical related program, that would be use while with no connection. When some action act, the program would write the time to CoreData record.
That's the problem, if their device set the time to a diff time like earlier than the real time. That would be a big problem coz it's for medical usage.
So, how can i get the "real" time even if there is no connection?
Or, is it possible to disallow user changing the device time using something like restrictions or DeviceProfile?
It's only because Apple IS the Big Brother they claimed to be fighting in 1984. Welcome to 1984! Otherwise we would have access to real time time, and an English version of ISO date format! :-/
Every iPwn, and now other devices, has a GPS receiver and an Internet capability, from which sub-second accurate time could be derived, yet Apple insists on forcing us to depend on AT&T to automatically set our clocks. It's only recently that AT&T started delivering accurate time, thank god for small favors.
The lack of GPS and NTP time setting, plus the glaring omission of ISO 8601 date formatting with otherwise USA formats and language, is extremely annoying on a daily basis.
So, the answer to your question is, Yes, it is feasible, but not in Apple's Jail, since you cannot set RTC from GPS or NTP without jail breaking.
PS: my guess is that AT&T insists on this for call-timing or something stupid that has to do with charging us more money! ;-)
You get the real time from [NSDate date]. For example, the following:
[[NSDate date] timeIntervalSince1970]
gives the number of seconds since 1/1/1970 midnight UTC. This is independent of timezone and independent of whatever time is set by the user. If you know the timezone, then you can convert that to local time with the NSDateFormatter if you like, but make sure to also record the timezone to make the representation unique.
EDIT: Sorry, this answer is actually not correct. After trying it out, it appears that setting the time by the user also changes the NSDate values.
So, how can i get the "real" time even if there is no connection?
If by "no connection" you mean "no network connection of any sort" the answer is that you can't.
I think the best you can do is disable the functionality if you can't find a way to independently verify the system time (and tell the user why).
NSDate and all associated classes read the date from the system time. Without an internet connection to refer to, the NSDate class is open to user abuse.
I used an example in a comment on fishinear's answer of Farmville. If the user plants some crops that take five hours to grow, you can just change the system time to five hours in the future to harvest. Which, I'm sure, is one of the reasons that Zynga requires an internet connection to play their games.
Without some time-telling hardware, Apple cannot realistically tell time without an internet connection; even if they did have some amazing solution, they'd have to take into account timezones and even travel across timezones in order to make this work.
If I were you, I'd require an internet connection at specified intervals (once a day or the like) in order to draw a reference.
Let us know why you need this and we may be able to suggest some viable alternatives in function.