On Saturday, 24 February 2018 08:15:39 GMT Terry Coles wrote: > I then went back to the suggestion made by Ralph a few days ago and captured > the packets on the network when the WiFi connection was made. In the > event, I didn't use tcpdump because I also wanted to see what the exchange > was when the system worked, ie, when I connected to a WiFi AP *with* > Internet Access. Instead, I installed an Android App called 'Packet > Capture', and used that; first with my home router and then by connecting > to the WMT AP. I got virtually identical exchanges each time, Here is the
I decided to try tcpdump as suggested by Ralph, because I realised that the Android App was obfuscating the information. I did two captures: 1. Using my wife's Nexus 5 phone (Android 6), which connects to the WMT AP without complaint. 2. Using my Moto G5+ phone (Android 7), which complains that the device has no Internet connection). In each case, I started a stopwatch when I sent the tcpdump command on the Pi, and took a lap time when: a. The Nexus showed a successful connection (approx 8 seconds). b. The G5 put up the 'No Internet' dialogue (approx 16s). I then continued capture for approx 1 minute. Analysing the results in Wireshark, my limited skills allow me to see that both devices sent a GET /generate_204 to connectivitycheck.gstatic.com and got a '204 No Content' response a total of six times. These GETs appear to continue even after the phone has accepted the AP in the case of the Nexus and complained about the AP with the G5. I can't see anything else much in this capture to help, except that both phones seem to query a number of other sites and get refused of course because they are not in my DNS. Strangely enough they seem to try an apple.com site! (It should be noted that the sites that the phone tries seem to be a bit arbitrary; I've seen other google sites queried in other captures, including google.com and android.clients.google.com.) I've put both capture streams up on my website at: http://hadrian-way.co.uk/Misc/Misc.zip If anyone with greater knowledge and experience than me could spare the time to have a look at these captures, I would appreciate it. -- Terry Coles -- Next meeting: Bournemouth, Tuesday, 2018-03-06 20:00 Meets, Mailing list, IRC, LinkedIn, ... http://dorset.lug.org.uk/ New thread: mailto:dorset@mailman.lug.org.uk / CHECK IF YOU'RE REPLYING Reporting bugs well: http://goo.gl/4Xue / TO THE LIST OR THE AUTHOR
