Q: iPhone 4s losing data connection multiple times/day

oh, maybe this is because I'm in Belgium (factory unlocked phone, and allows me to select my carrier of choice?). It does not make sense when at home, as my carrier does not have roaming with another Belgian carrier :-) ).

This is what I see when selecting Settings -> Carrier:

Had the problem again and this time I hooked up to Xcode to check the log-messages. There I found that mdnsResponder is basically running amok with these messages repeated 2-3 times every second:

Feb 13 11:40:19 unknown mDNSResponder[34] <Error>: ERROR: mDNSPlatformReadTCP - recv 56 got CLOSED 2576000 times

Feb 13 11:40:19 unknown mDNSResponder[34] <Error>: ERROR: mDNSPlatformReadTCP - recv 56 got CLOSED 2576000 times

Seems like something in the network-stack (Bonjour?) is out of control.

Any ideas?

Carsten

I experienced the problem yesterday and today and it was resolved with a restart of the iPhone.  I did notice today that while the data network outage was occuring, the iPhone 4S's battery was draining incredible fast compared to how fast it would normally run down.  For example, it 2 hours it dropped by 50% where as that drop would normaly have taken 6-8 hours of high usage to experience.  I agree that some process must be running in an out of control loop or something when the 3G data connections is not working but looks like it is connected.

This is not a carrier issue.  In the past two weeks, I have had too many 'no service/searching' messages to count dropping calls and text messages.  I have been to ATT 3 times and receivved 2 new SIM cards and validated the peformance of the network.  Not a problem there.  My husband has the exact same phone (4S /64) and has no problems.  He has not updated his version (currently has 5.0 / 9A334).  I did not have this issue until I updated my OS. I am now on 5.0.1  I have done all different things to try to resolve this problem under the guidance of ATT,

phone support and the genius bar (they were all at a loss to find a solution) and all within the last 9 or so days:

• two new phones
• restore (twice)
• Restore with iCloud
• Restore from desktop
• Reset networks settings
• Replaced two SIM cards
• Almost all the recommedations made prior to my posting

I could be wrong, but if I had to make a guess (why not everyone else is guessing on solutons), apple know there is a serious bug in the operating system of the phone and do not want to admit it and will let us thrash until they find a solution.  The last upgrade to the OS was supposed to fix it and it did not so they are back to the drawing board.  I did hear that theere is a new version in beta.  It will be released with not even an acknowledgement of the issues we are all having.  Not cool from a customer service point of view.  Would respect more tranparency instead of letting good customers spend hours (there is a cost to that) running back and forth to stores and on the phone with customer support.  CS needs to make it to the top of their list as this is unacceptable. If I am right, this is really arrogant.

bumping this thread as I'm having the exact same problems some of you guys are having. No issues with the sim card, but I am losing data connection. AT&T carrier in the Los Angeles area.

Phone was bought with the latest version of ios5.

Randomly throughout the day, I will lose data connection despite showing full signal bars and the 3G icon. The only solution is to either hard reset or switch airplane mode on and off. Data will miraculously be okay afterwards. Also have a iPhone4 with no problems so I doubt it's the reception quality.

Went to the Apple Store and was given a new phone. Was good for one day, but started again the next day. Apple or AT&T really needs to fix this ASAP.

Looking round a little, I found out that "mdnsresponder" is a part of the bonjour framework.

Since I do not use bonjour at home for anything, I am pretty sure that the only case where my iOS devices us this is "WLAN sync". This corresponds also nicely to the appearance of my problems, right about the time iOS 5 was introduced. Never had this problem with iOS 4.

So, I turned off WLAN sync (never had much use for it anyway) about 10 days ago and did not have this problem again.

Maybe this is really the solution.

Funny thing is, my MacBook Pro from 2007 also has the problem that mdsnResponder runs wild, and much more frequent than the iOS devices. Seems like my network setup is really not bonjour friendly...

Let me start with the fact that mine has been fixed for two solid weeks with no service interruptions whatsoever. Prior to that I was two months with no service at my home but I could walk to the end of my driveway and it worked just fine. Replaced phone, replaced Sim card, multiple calls to AT&amp;T, shut down wireless network at home, nothing seemed to work other than leaving the house. I continued to call AT&amp;T to talk to them about the problem explaining that the phone had worked perfectly for a couple of months after I bought it. I was beginning to wonder whether I had even remembered it correctly. We had a weekend where the 3G went down in this area and we only had edge connectivity and the phone worked perfectly from any room in the house including the basement. I don't know if that helped to convince them that there was a network problem but it convinced me that there was nothing wrong with the phone and that something must be wrong with the with the way the network was configured. It took about a week after that for them to call me back and say that they thought they had fixed the problem and in fact they had. Other than an occasional switch back to edge because 3G is down, it has been working perfectly.

Obviously this is not the answer to all of the problems that have been posted here but for some of you there is certainly a network issue that they can fix if they work at it.

Good luck

i have the same problem: losing internet connection both while on wifi and mobile data. funny thing is the wifi icon shows strong signal, but when i tried to check my mails/twitter it says i have no internet!! this is really frustrating!!!

Good to see I'm not the only one having the problem.   I have an iphone4s with 64gig on AT&T.  The phone worked fine for several months but then started on rare occasion having this connectivity issue.   Now it is every 3 or 4 days that the problem occurs. 

The issue is the same as others, I have a good signal on AT&T 3G.   However, no 3g data services will function, none of the applications will communicate, Safari will not work as well as Siri says "there is some problem".  Sometimes turning on Airplane Mode and turning it off will kick it into working again.  This last time connecting to a WIFI network the WIFI network worked fine but when I turned off WIFI the 3g still wasn't working.  However, I seem to recall sometimes WIFI will not work.  You don't notice 3g data isn't working until you try something.  Also SMS messaging doesn't work at this time as well., I can't send or receive text messages.   So the whole problem seems to surround the 3g network.  AT&T is upgrading their 3G networks, I wonder if they are causing a problem?  The only communications which will work is the voice functions of the phone. 

It seems to perhaps have something to do with traveling or perhaps going in and out of various WIFI networks or coverage areas but I can't pin it down as to an exact pattern.   This week was just going between home and work when I discovered it wasn't working.

Powering off the phone and back on always fixes the problem though.

.... Gary

Interesting you should say that, my battery drained 20% in a very sort period, I thought it was strange when I saw it, it wasn't until an hour or so later that I discovered 3g data services were not operating.

How do you turn off WLAN sync?

Uncheck the option in iTunes. Then sync.

I also had the same issue on my iPhone 4S, and I tried everything: Restored my phone as new, reset my networks, toggled the airplane mode, got a new SIM card, got a new phone.

So this last time I went to the genius bar, and the guy who helped me happened to have worked for AT&T. He advised me to call AT&T tech services, ask them to "reprovision" my phone. So when I called, they asked for my IMEI number (Settings>About>IMEI), which wasn't even close to what AT&T had assigned for my phone. So AT&T updated it and had me shut down my phone for 15 min and restart. The next day it still lost connection, so I thought I maybe I should reset my network. And voila! That seems to have done the trick (this is 3 weeks and counting).

Long story short:

1. Called AT&T and had them reprovision my phone.

2. Reset my network settings.

Hope this does the trick for everyone!

Updating to 5.1 did nothing to solve the problem for me, in fact it seems to be happening more frequently now...