Hi Sebastian,

thanks for the quick reply!

Cellular data was already disabled, and options to fallback to cellular when WiFi was not good enough was disabled as well. Client isolation was turned off as well in the AP.

Now, I think I have solved my problem. Today I managed to get Whisper messages and beacons exchanged on an AP without any Internet connection! I used the same parameters on IBR-DTN as indicated in my previous email.

To make it work, I had to consider the following things:
- on one of the phones, the advanced WiFi setting "Wifi in standby mode" (or equivalent, I am translating from French) was set to Never. I changed it to Always.
- I am using very aggressive energy management settings, which means the phones go to sleep mode very fast when no action is performed on them. Unfortunately for me, in such cases IBR-DTN reduces the beacon frequency as well by a factor of 10 (50 seconds instead of 5), so one may think that no beacon gets exchanged.
- I think I found a bug on IBR-DTN. I managed to reproduce this behavior on both phones (Android 4.1.2 and 6.1.0). I am using the version "app 1.0 dtnd 1.0.1 build 570f2b9", directly installed from the Play store.

Here are the steps to reproduce the bug:
Start the WiFi and the IBR-DTN application.
On the IBR-DTN application, activate the switch. Check that beacons are actually being sent.
Deactivate the switch.
Put the IBR-DTN app in the background, for example by pressing the Back key on the phone.
Start the IBR-DTN app again, either by clicking on the icon or by fetching it from the task manager.
Activate the switch again.

In this case for me, no beacons are being produced, i.e., nothing appears in the log or in Wireshark. The solution I found is to deactivate the switch, kill the IBR-DTN application through the task manager and restart it again.
Note that when the switch remains activated, I did not notice any issue when putting the IBR-DTN app on the background.
Similarly, when the switch is deactivated and the application is not put in the background, switching on again works properly.

Cheers,

Gwilherm Baudic

Le 17/02/2016 20:23, Sebastian Schildt a écrit :

Hi Gwilherm,

while I am not 100% sure, this might actually be an android „feature“: When an Android device is on a  Wi-Fi without iNternet connection, it will usually detect this and use the cellular connection.I am not usre, that maybe even without cellular, it might still ignore the Wifi. Things you can try

 - Switch off celluar data
 - Most Androids have something like „avoid poor Wi-Fi connections“ in their Wi-Fi settings. Turn this feature off.

Another thing is, that Beacons are using multicast/broadcast. So it usually only works if „client isolation“ is turned off in the AP (it is not always straight forward to see or find this feature in consumer APs, so you might have to try). If you are sure one Android sends beacons, join the same WiFi wit a PC and use Wireshark to see, whether you receive multicast or broadcast frames from other devices connected via WiFi)



Sebastian

On 17 Feb 2016, at 16:38, Gwilherm Baudic <gwilherm.baudic@isae.fr> wrote:

Hello everyone,

I am currently experimenting with the IBR-DTN application for Android in
order to get familiar with it. More specifically, my setup is as follows:
* 2 Android smartphones (Android 4.1 and 6.1.0) running IBR-DTN from the
Play store (app 1.0 dtnd 1.0.1 build 570f2b9) and Whisper 1.6, also
downloaded from the Play store. Smartphones do not have any 3G/4G
connection enabled and only have Wifi available for the experiment.
* 1 Wifi access point to which both smartphones are connected.

What I am trying to achieve is very simply, as a first step, to check if
both phones can see each others as neighbours (in the Neighbor list of
IBR-DTN), and try to transfer some Whisper text messages between them.

The settings on IBR-DTN are:
Epidemic routing
Discovery policy always on
Cloud connect Off
Wifi direct Off
Security is deactivated
Time synchronization is also deactivated
Log parameters are set to Debugging with verbosity level 99 and I chose
to save the text files as well for further inspection.

I experimented with several access points (ISP router at home, campus
Wifi, dedicated router on my desk in the lab). From the observations I
made from the phones and the log files, it seems that beacons are
getting produced (and exchanged) only when the access point has a
connection to the Internet.
I feel like I am missing something here, and that the actual reason for
the lack of beacons is totally unrelated to the Internet connectivity.
Does anyone have any idea on this?



On a side note, the naming scheme for the log files looks rather strange
to me. For example, for a log file starting on February 15th, 2016 at
16:15:02, the resulting filename I obtain is 2016115154152 while I would
expect something closer to 20160215161502. With the changing length, the
current naming scheme has the drawback of breaking the alphabetical
order, thus making it really inconvenient to work with lots of files
with different start dates. 

Best regards,

Gwilherm Baudic
PhD student, ISAE-SUPAERO
-- 
!! This message is brought to you via the `ibr-dtn' mailing list.
!! Please do not reply to this message to unsubscribe. To unsubscribe or adjust
!! your settings, send a mail message to <ibr-dtn-request@ibr.cs.tu-bs.de>
!! or look at https://mail.ibr.cs.tu-bs.de/listinfo/ibr-dtn.