I have packet analyzed my dns packets and I am still getting UnknownHostException with a successful resolution on the emulator.
On Jan 17, 7:53 pm, Indicator Veritatis <mej1...@yahoo.com> wrote: > Excellent post! I have only one small detail to add; it might actually > turn out to be important, though I can't guarantee it. That detail is: > DNS is almost always implemented using UDP for transport, not TCP, so > there is none of TCP's measures to try to provide guaranteed delivery. > Instead, the DNS client (a.k.a. the 'resolver') will retry a few > times, then quit. How many times is up to the implementer. > > So though it may be difficult (since the Exception is random), I would > consider it worth the bother to run Wireshark captures while doing the > DNS search, and see what shows up when the OP get > UnknownHostException. > > Now here is why my one point may be so relevant: the resolver is > linked into the Linux application, so it can be different even for two > different applications running on the same phone (though this is > unlikely, especially if all are Android Java apps). Then there are > configuration parameters passed to the resolver function calls. It is > not a separate daemon as are most application level networking > clients. So this could explain why the OP gets the failures only with > this one application and not with other hosts or other applications on > the same phone. > > So is the OP's application pure Android Java, or did he use the NDK? > What about other applications running on the same phone? If all > Android Java applications fail randomly just like the OP's own > application, while some NDK applications work, then the problem is > most likely with the phone's implementation of the resolver for > Android Java (less likely the WiFi itself). But again, to really be > sure what is going on, LogCat is not enough: we need the Wireshark > captures, preferebly on with tehe failure adn one without, so that we > can see how your phone implemented and configured the resolver: not > everyone uses BIND. > > There are other variations possible. To distinguish between them, the > Wireshark captures are the way to go. > > Finally, whose DNS server is the OP using? Google's is pretty good, > response time is excellent. And it is quite capable of handling either > IPv6 or IPv4. If he sets up a local DNS server, not only can he have > total control, it makes it a lot easier to GET those Wireshark > captures. Unfortunately, we can't run Wireshark on even a rooted > Android phone. If you can't do the local server, and can't run > Wireshark on the WiFi AP, then it may even be worth the effort to fake > it, running a simple Java program inside your LAN that does not do the > whole DNS, but spits back a canned DNS response. I have done this > before with success. > > On Jan 12, 11:00 pm, Bob Kerns <r...@acm.org> wrote: > > > > > > > > > UnknownHostException means your device was unable to get a positive > > response to the DNS query trying to look up the hostname. > > > It doesn't distinguish between "We couldn't talk to the DNS server", > > "we have no network connection right now", "we have never even HEARD > > of net work, what's that?", or "we carefully and thoroughly discussed > > it with the DNS server, which in turn discussed it with the relevant > > authoritative DNS servers, and can conclusively state, that the host > > named does not exist at this time". > > > What you CAN say, is it never got to the point of actually trying to > > talk to that host, because it didn't get enough information to do so. > > That is, it is not saying "we've heard of that host, but it doesn't > > seem to be there". > > > The most likely cause is a temporary failure in your wifi connection, > > just as it was trying the DNS lookup. But the DNS server itself could > > be to blame, or if it's a DNS server on your site, the connection > > upstream, or an upstream DNS server could be to blame. > > > I use my local wifi server as a DNS server. It's been giving me > > problems like this lately, even on wired connections. Plus, it is not > > compatible with IPv6, so I'm going to need to upgrade it soon. I could > > configure it to advertise OpenDNS servers instead (which is what it > > itself is using), but have slightly longer lookups and no cached data > > if the cable connection hiccups. If it's the cable connection that's > > at fault, then I'll have these problems anyway. It won't be easy to > > track down. > > > On Jan 12, 8:44 pm, Ankur Avlani <ankuravl...@gmail.com> wrote: > > > > Unfortunately, the server is not local. > > > > On Wed, Jan 12, 2011 at 4:15 PM, Dan <king...@gmail.com> wrote: > > > > Hello All, > > > > > I have had this error both on emulator and a Motorola Droid while > > > > using a WIFI connection. I have surrounded the http request with WIFI > > > > state checks and before and after WIFI is reported state 3 > > > > (WIFI_STATE_ENABLED) and a connection speed of 54 . I have also > > > > confirmed, using an adb shell with the emulator, that the emulator > > > > cannot ping the website in question giving a domain resolution error. > > > > To compare notes with Ankur, is the server on your LAN and the IP used > > > > internal? mine is. > > > > > I have also tried AndroidHttpClient which does work on the same url. > > > > > -Dan > > > > > On Jan 12, 12:23 pm, Ankur Avlani <ankuravl...@gmail.com> wrote: > > > > > True, I agree with what you say. Its just that I feel, other apps > > > > > should > > > > > also break or give error. > > > > > > Anywayz, Thanks a lot for your inputs. > > > > > > regards, > > > > > Ankur. > > > > > > On Wed, Jan 12, 2011 at 12:17 PM, Brill Pappin <br...@pappin.ca> > > > > > wrote: > > > > > > Well i suppose thats possible if your messing with the network > > > > > > stack, > > > > > > but it's pretty low level for Java/Android. > > > > > > I guess its also possible that the Android version you have has a > > > > > > crappy stack or driver... or you have rooted it and have been > > > > > > messing > > > > > > around under the covers so to speak. > > > > > > > There is nothing in Android really that would allow you to mess it > > > > > > up > > > > > > that badly AFAIK, so I doubt it's your application causing the > > > > > > problem > > > > > > if your not specifically getting under the covers. > > > > > > > However, the meaning of the exception is clear: > > > > > > >http://download.oracle.com/javase/1.4.2/docs/api/java/net/UnknownHost. > > > > .. > > > > > > and your app doesn't really control the process of translating a > > > > > > domain to an ip. > > > > > > > - Brill Pappin > > > > > > > On Jan 12, 2:54 pm, Ankur Avlani <ankuravl...@gmail.com> wrote: > > > > > > > Somehow I have this feeling it is related to my app only. Other > > > > > > > apps > > > > on > > > > > > the > > > > > > > phone, I don't see any such issue. Even when browsing on my > > > > > > > phone, I > > > > > > don't > > > > > > > see any error. > > > > > > > > On Wed, Jan 12, 2011 at 11:41 AM, Kumar Bibek > > > > > > > <coomar....@gmail.com> > > > > > > wrote: > > > > > > > > By Wi-Fi, I meant, you phone's Wi-Fi could be turning on and > > > > > > > > off. > > > > There > > > > > > is > > > > > > > > no other reason I can think of. It happens for me as well, > > > > sometimes. > > > > > > > > > Kumar Bibek > > > > > > > >http://techdroid.kbeanie.com > > > > > > > >http://www.kbeanie.com > > > > > > > > > On Thu, Jan 13, 2011 at 1:10 AM, Ankur Avlani < > > > > ankuravl...@gmail.com > > > > > > >wrote: > > > > > > > > >> I am sorry, that somehow doesn't convince me. I am connected > > > > > > > >> to > > > > the > > > > > > same > > > > > > > >> wifi on my laptop and i never see any web page load error on my > > > > > > laptop. > > > > > > > > >> On Wed, Jan 12, 2011 at 11:38 AM, Kumar Bibek < > > > > coomar....@gmail.com > > > > > > >wrote: > > > > > > > > >>> Yup, then it's a problem with your Wi-Fi. > > > > > > > > >>> Kumar Bibek > > > > > > > >>>http://techdroid.kbeanie.com > > > > > > > >>>http://www.kbeanie.com > > > > > > > > >>> On Thu, Jan 13, 2011 at 1:07 AM, Ankur Avlani < > > > > ankuravl...@gmail.com > > > > > > >wrote: > > > > > > > > >>>> I am connected to network, I am on Wifi. If i try again it > > > > works. > > > > > > Its > > > > > > > >>>> just random. > > > > > > > > >>>> On Wed, Jan 12, 2011 at 11:34 AM, Kumar Bibek < > > > > coomar....@gmail.com > > > > > > >wrote: > > > > > > > > >>>>> This error/exception comes because of no network > > > > > > > >>>>> connectivity. > > > > > > > > >>>>> Kumar Bibek > > > > > > > >>>>>http://techdroid.kbeanie.com > > > > > > > >>>>>http://www.kbeanie.com > > > > > > > > >>>>> On Thu, Jan 13, 2011 at 1:02 AM, Ankur Avlani < > > > > > > ankuravl...@gmail.com>wrote: > > > > > > > > >>>>>> Hi All, > > > > > > > > >>>>>> I am developing an application on Android. I have seen > > > > > > > >>>>>> that > > > > at > > > > > > times > > > > > > > >>>>>> when I try to connect using HttpURLConnection, for getting > > > > > > > >>>>>> an > > > > > > Image or > > > > > > > >>>>>> anydata, I get the following error: > > > > > > > > >>>>>> 01-12 11:24:05.073: WARN/System.err(16780): > > > > > > > >>>>>> java.net.UnknownHostException: Host is unresolved: > > > >www.XXX.com:80. > > > > > > > > >>>>>> Note: I get this error on my Motorolla Droid and not in > > > > emulator. > > > > > > > > >>>>>> Any ideas? > > > > > > > > >>>>>> Thanks, > > > > > > > >>>>>> Ankur > > > > > > > > >>>>>> -- > > > > > > > >>>>>> You received this message because you are subscribed to the > > > > Google > > > > > > > >>>>>> Groups "Android Developers" group. > > > > > > > >>>>>> To post to this group, send email to > > > > > > > >>>>>> android-developers@googlegroups.com > > > > > > > >>>>>> To unsubscribe from this group, send email to > > > > > > > >>>>>> android-developers+unsubscr...@googlegroups.com<android-developers%2Bunsubs > > > > > > > >>>>>> cr...@googlegroups.com><android-developers%2Bunsubs > > > > cr...@googlegroups.com><android-developers%2Bunsubs > > > > > > cr...@googlegroups.com> > > > > > > > >>>>>> For more options, visit this group at > > > > > > > >>>>>>http://groups.google.com/group/android-developers?hl=en > > > > > > > > >>>>> -- > > > > > > > >>>>> You received this message because you are subscribed to the > > > > Google > > > > > > > >>>>> Groups "Android Developers" group. > > > > > > > >>>>> To post to this group, send email to > > > > > > > >>>>> android-developers@googlegroups.com... > > read more » -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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