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Old 02-13-2018, 10:17 AM
Jinx Jinx is offline
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A&Q? A Text Flaw, but how?

Apparently, a recent iOS version update has a flaw where Apple SmartPhones can see texts out of order. Specifically, answers "post" before the questions! While I have found alleged fixes to this problem online (such as rebooting the phone), my question is WHY & HOW does this happen? Please explain what is happening inside the widget iPhone we treat as a black box.
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Old 02-13-2018, 12:49 PM
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beowulff beowulff is online now
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Sounds like a multithreading issue to me.
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Old 02-14-2018, 03:30 PM
biometricks biometricks is offline
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I'm having this problem with iOS 11. The fixes haven't helped. It only happens if the person responds within a few seconds of my text. It seems like the clock is off by a few seconds.
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Old 02-14-2018, 05:21 PM
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Kyrie Eleison Kyrie Eleison is offline
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Quote:
Originally Posted by biometricks View Post
It seems like the clock is off by a few seconds.
This. I don't know exactly how, but they broke clock synchronization somehow, which is kind of impressive in a device that has GPS and connects to cellular networks.

I've seen this happen twice to my phone recently. If you slide your messages to the left, you can see the timestamps assigned to them. Messages I sent in response to someone else, who was also using an iPhone, appeared with timestamps earlier than the messages they were in response to. When I sent them, they at first appeared in the right order, but in a second or two, the app sorted them, and reordered them according to their incorrect timestamps, making it appear that I'd sent my response prior to the inquiry it was in response to. Rebooting my phone fixed the problem both times.

So either the clock itself is wrong, or, technically, maybe some sort of error is being made in assigning timestamps to messages.
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Old 02-14-2018, 06:22 PM
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For what it's worth, I've also occasionally seen this on my Android device.
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Old 02-15-2018, 04:21 PM
sbunny8 sbunny8 is offline
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It happens to me quite frequently when texting with my spouse and we are both using Android devices. I have also noticed that our clocks are often off from each other by exactly 60 seconds, despite both phones being set to adjust time and date automatically from the (same) network.
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Old 02-15-2018, 04:38 PM
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Happens to me all day long. I text frequently with people who are also on iOS and Verizon just like me. It's been happening through about 4 updates now.
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Old 02-17-2018, 11:19 PM
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But why wouldn't they just put a timestamp from the device when the text is received and sort by that, making sure they're always using the same clock for both outgoing and incoming texts? That seems the obvious way to do it.

Never rely on two different clocks being in sync if you can avoid it.

Last edited by BigT; 02-17-2018 at 11:20 PM.
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Old 02-18-2018, 10:25 AM
sbunny8 sbunny8 is offline
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Quote:
Originally Posted by BigT View Post
But why wouldn't they just put a timestamp from the device when the text is received and sort by that, making sure they're always using the same clock for both outgoing and incoming texts? That seems the obvious way to do it.

Never rely on two different clocks being in sync if you can avoid it.
Maybe because the network itself is sluggish in delivering the message and they want to reflect the time it was sent rather than the time it was received.

Allow me to clarify; here's an example.

Step 1, I send a text at 6:03 saying "I'm at the grocery store. Want anything?" I wait a few minutes and get no reply, so I assume my wife didn't have anything to say.

Step 2, I send another text at 6:05 saying "I'm in the checkout line now."

Step 3, at 6:06 I receive a text message from my wife saying "No thanks!" and it is timestamped 6:04. But I didn't receive it until AFTER I sent the second message at 6:06.

Step 4, my phone insists on rearranging the message like this, based on the timestamps:

6:03 I'm at the grocery store. Want anything?
6:04 No thanks!
6:05 I'm in the checkout line now.

But that's not the sequence that I saw it happen.

Slight hijack, this reminds me an incident 20 years ago when I sent a fax from the Eastern time zone to the Mountain time zone, sent it at 9:30pm Eastern (which is 7:30pm Mountain). The recipient was awakened by their phone ringing around 10-ish but did not answer it, went downstairs the next morning to see a fax from me timestamped "9:30 pm" and then proceeded to get mad at me for waking them up after bed time. I never did manage to persuade that person that there must have been two different phone calls and the one that woke them up wasn't me. Timestamps on faxes are recorded by the sending device, in the sender's time zone, and depend on the internal clock of the sending device.
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Old 02-19-2018, 12:39 PM
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Possibly related? I have an Android phone and my stepdaughter has an iPhone. If she sends me a text message longer than a few sentences, I will receive it in two or three different chunks that display out of order. I have not seen this happen with Android to Android texts.

On the other hand, she has AT&T and we have Verizon, so it may be carrier-related and not phone-related?
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Old 02-19-2018, 01:19 PM
Francis Vaughan Francis Vaughan is offline
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I had a look at a few of the Apple related bug discussions, and the answer is I suspect messy (at best). Apple are not saying what the problem is, but they do seem to be suggesting that people reset the timezone information on their phones, and then set it back, or similar tricks.
The SMS protocol tags messages with the time they are received at the SMS centre in time local to that centre with a tag for the time zone offset. I'm going to bet that other protocols have similar weirdness (why not use UTC everywhere?). The problem that phones may have is that messages are received by the phone with timestamps that require additional interpretation. There isn't a simple idea of "the time" when a message was received (and indeed, this time may be significantly different to the time it was sent.) Plus the timezones of the sender, receiver, and message centre might all be different. So, if somewhere in the software on the phone there is a glitch in how timezones are handled (and this includes daylight saving time offsets), especially something that messes up the translation to and from different timezones to UTC, the whole thing could come quite unglued. iPhones are built on top of Darwin, which is a Mach/BSD fork. That (like any Unix system) uses UTC internally for all time. We hope that the message system uses UTC as well. I would also hope that Apple's own iMessage system uses UTC. But it must interact with other message protocols that use local times and offsets. It isn't too hard to see how something could get messed up in the code and let things get sufficiently wrong that it all ends in tears.

Last edited by Francis Vaughan; 02-19-2018 at 01:21 PM.
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Old 02-19-2018, 01:39 PM
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Quote:
Originally Posted by Francis Vaughan View Post
The SMS protocol tags messages with the time they are received at the SMS centre in time local to that centre with a tag for the time zone offset. I'm going to bet that other protocols have similar weirdness (why not use UTC everywhere?).
Oh please tell me this is not true. I've spent so much time trying to convince fellow programmers that you NEVER use local time for anything except display to the user. For example, what happens during the hour in November when the local time is ambiguous?
  #13  
Old 02-19-2018, 03:46 PM
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SMS messaging is packet-switched - the data is exchanged asynchronously across the network (the size of the packets was actually part of the reason that SMS messaging used to have a strict size limit.

Packet switched networks don't necessarily have to guarantee that every packet of data gets to the destination in the same order as sent, or at all - some packets can be dropped and will be re-sent - usually this is pretty transparent to the end user when doing tasks such as web browsing (the internet is also packet switched), but when it comes to tiny discrete bits of data such as text messages, a single lost packet matters a whole lot more.
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Old 02-22-2018, 12:17 PM
biometricks biometricks is offline
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I just happened to send a text at exactly 12:00pm, but I noticed the timestamp of the text was 12:01pm. So I went to the clock to see how close it was to 12:01pm and the clock was at about 12:00:15pm. So it looks like the timestamp of messages that I send are 45-60 seconds fast, but when I receive a message it's using the correct (or wrong?) time and thus if I get a quick response it puts it chronologically ahead of the message that I sent.

It's led to some very confusing conversations.
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Old 02-22-2018, 04:51 PM
Francis Vaughan Francis Vaughan is offline
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Quote:
Originally Posted by biometricks View Post
I just happened to send a text at exactly 12:00pm, but I noticed the timestamp of the text was 12:01pm. So I went to the clock to see how close it was to 12:01pm and the clock was at about 12:00:15pm.
I wonder if what you saw was the time on the delivery receipt? That isn't generated in your phone but is generated by the recipient.

Having phone handsets with slightly varying clocks could cause problems as well. I didn't mention this before for two reasons. One - Apple were suggesting DST issues and related fixes for the problem. Two - phones generally take there time from the connected cellular network. Cell networks rely upon extremely tight time, and you phones will be accurate to a very small fraction of a second. But this isn't going to always be the case - you might not be in contact with a cellular network and are relying on a WiFi connection, or you might be using a messaging agent on something other than a phone. So it is possible to see how small offsets in time occur. The messaging programs will find it impossible to sort message order out of the various participants tag their messages with varying times. The system relies upon everyone agreeing on the time and tagging messages and receipts with that time.

Makes me wonder if the various fiddling with DST settings isn't just a way of forcing the phone to try to regain sync - but that is a pretty brutal thing to do.
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