A network time protocol client and application testbed for iOS. This is a continues to be a work in progress.
Created by Gavin Eadie on Oct 17, 2010
November 19, 2014: A large update was made today to bring ios-ntp into the modern world. The changes do include one bug fix, but are mostly related to making the code comply with the recent Xcode changes and requirements. Such things are sometimes tricky, so make sure you test carefully when you adopt today's changes.
Some of jbenet's "Usage" notes below aren't completely accurate as a result of these changes, and I will update the text soon.
Finally, note that this code was written when there were only 32-bit iOS devices. As I write this there are still 32-bit devices which run the latest version of iOS (iPhone 4S, for example), but all newer iOS devices have a 64-bit architecture (iPhone 6, for example). Since the representation of "Unix time" uses an 'signed long' for seconds since Unix epoch (01 Jan 1970), this value rolls over on 19 Jan 2038 on older iOS devices. This is not too worrying, however, since "NTP time" rolls over before that, on 08 Feb 2036. Which is all by way of saying (a) be careful with arithmetic, and (b) you should not be using this code in 20 years, or setting your device's clock past 2038 !!
The clock on an older iPhone, iTouch or iPad is not closely synchronized to the correct time. In the case of a device which is obtaining its time from the telephone system, there is a setting to enable synchronizing to the phone company time, but that time has been known to be over a minute different from UTC.
In addition, users may change their device time and severely affect applications that rely on correct times to enforce functionality.
This project contains code to provide time obtained from standard time servers using the simple network time protocol (SNTP: RFC 5905). The implementation is not a rigorous as described in those RFCs since the goal was to improve time accuracy to less than a second, not to microseconds.
November 19, 2014: jbenet and I (gavineadie) have agreed that I will resume taking care of this project and will let the old version at Google Code fade away. I've come to enjoy git much more than svn also.
This is a fork from the original source at http://code.google.com/p/ios-ntp/ that provides ios-ntp as a static iOS framework. This makes its use easier and avoids symbol clashing.
Why fork? Well, because git and github are much more convenient than google code for me. I (jbenet) am subscribed to the RSS feed of the original project and will merge any upstream changes.
The MIT License Copyright (c) 2010-4, Ramsay Consulting
November 19, 2014: Some of the words below are not true. That will be fixed soon.
Download ios-ntp.tar.gz,
and add ios-ntp.framework to your project. Make sure the file ntp.hosts is
added to the project. I should show within the ios-ntp.framework/Headers
directory.*
This project depends on CocoaAsyncSocket, so you may need to
get it. ios-ntp only needs
AyncUdpSocket.
Edit ntp.hosts to add or remove any NTP servers. Make sure it is OK to use them.
Then, simply call:
[NSDate networkDate];
As soon as you call it, the NTP process will begin. If you wish to start it at boot time, so that the time is well synchronized by the time you actually want to use it, just call it in your AppDelegate's didFinishLaunching function.
- Note: The ntp.hosts is currently inside Headers to both bundle it with the framework AND coax Xcode to automatically add it, as it does not add the Resources directory of frameworks.
To build the static framework, build the ios-ntp target from the xcode
project. Make sure you build BOTH the iPhone Simulator and iOS Device
architectures.