A network time protocol (NTP) client.

The clock on the oldest 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 the correct time.

In addition, users may change their device time and severely affect applications that rely on correct times to enforce functionality, or may set their devices clock into the past in an attempt to dodge an expiry date.

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 that document since the goal was to improve time accuracy to tens of milliSeconds, not to microseconds.

Computers using the NTP protocol usually employ it in a continuous low level task to keep track of the time on a continuous basis. A background application uses occasional time estimates from a set of time servers to determine the best time by sampling these values over time. iOS applications are different, being more likely to want a one-time, quick estimate of the time.

• iOS 7 and later.
• Objective C, and Swift with bridge header (read below guide)

Add below line to Podfile:

pod NHNetworkTime

and then run below command in Terminal to install:
pod install

Note: If above pod isn't working, try using below pod defination in Podfile:
pod 'NHNetworkTime', :git => 'https://github.com/huynguyencong/NHNetworkTime.git'

Add all file in folder NHNetworkTime to your project. Then add CocoaAsyncSocket use Cocoapod or add manual.

Import this whenever you want to get time:

#import "NHNetworkTime.h"

Call synchronize in - application: didFinishLaunchingWithOptions: to update time from server when you launch app:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [[NHNetworkClock sharedNetworkClock] synchronize];
    return YES;
}

then you can get network time when sync complete in anywhere in your source code:

NSDate *networkDate = [NSDate networkDate];

or add notification to re-update your UI in anywhere you want when time is updated:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(networkTimeSyncCompleteNotification:) name:kNHNetworkTimeSyncCompleteNotification object:nil];

#####Use use_frameworks!

If you have use_frameworks! option in Podfile, import NHNetworkTime framework in each code file use NHNetworkTime objects:

@import NHNetworkTime

Import NHNetworkTime.h to your in bridge header file:

#import <NHNetworkTime.h>

• You can create bridge header file by create an Objective C file in project. Xcode will ask you to create bridge header file. After, you can delete the temporatory Objective C file have just added, and import NHNetworkTime.h into there (Read more: https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html)

Now, you can call below code in your code:

NHNetworkClock.sharedNetworkClock().synchronize()

and:

NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("syncCompleteNotification"), name: kNHNetworkTimeSyncCompleteNotification, object: nil)

• Use NSNotifcationCenter to add observer kNHNetworkTimeSyncCompleteNotification to receive notification when time sync complete
• Property isSynchronized: Check network time synchronized or not
• Property shouldUseSavedSynchronizedTime: Should use offset time saved in the last synchronization before sync from server. Default is YES.
• Property isAutoSynchronizedWhenUserChangeLocalTime: Is auto sync when user change local time. Default is YES.

Add to project file name ntp.hosts, with content is time server address in every line. If file is not exist, it will use default time server. Example for ntp.hosts file:

asia.pool.ntp.org
europe.pool.ntp.org
north-america.pool.ntp.org

NHNetworkTime is built from ios ntp open source from jbenet. NHNetworkTime fixed a critical bug get wrong time from origin source, and added more improvements:

• Post notification when sync complete
• Property make you know whether sync complete or not
• Save offset time local to use immediately right after launch app, don't have to waiting for server
• Auto sync when user change local time

NHNetworkTime is released under the Apache license. See LICENSE for details. Copyright © Nguyen Cong Huy