Le 26 mars 2014 à 12:09, Coiso22 a écrit :
> Hi all,
>
> I am trying to synchronise the time of an Android device with a local
> machine, for test purposes, using ntp. However, the difference between the
> time of the device and the ntp server is always around 5 milliseconds.
>
> Is there any way to synchronise the device with milliseconds accuracy?
>
> Here is my test scenario configuration:
>
> Android Server:
> This is a machine running Debian that will be used as the ntp server and will
> send traffic to the Android device. This machine is connected with an
> Ethernet cable to have internet access
>
> Android AP:
> This machine is running Debian and acts as an Access Point. It is also
> connected to the Android Server with an Ethernet cable.
>
> Android Device:
> An Android device with root access. It is connected to the Android AP via
> WiFi. This device will receive the traffic generated by the Android Server,
> and must be synchronised with it.
>
> Some notes:
> I do not need the Android Server to be synchronised with an external ntp
> server. Therefore, I changed the ntp.conf to have only "server 127.127.1.0".
>
> In order to synchronise the Android device I use the ntpd and have also tried
> with ntpclient. However, the results are very similar.
You could take out any network transmit/receive asymmetry by having the
server broadcast and configure the android device as a broadcast client.
As a quick test I pulled the ethernet cable on my laptop and configured wifi
so I have a similar topology to you , though BSD. It is configured in standard
client/server mode.
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 34:15:9e:01:e5:9c
inet 192.168.1.12 netmask 0xffffff00 broadcast 192.168.1.255
media: autoselect (100baseTX <full-duplex,flow-control>)
status: active
electron:~ mike$ ntpq -pn
remote refid st t when poll reach delay offset jitter
==============================================================================
*192.168.1.4 .PPS1. 1 u 49 64 377 0.938 -0.284 0.037
# pull the ethernet cable and configure wifi
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether f8:1e:df:e4:49:41
inet 192.168.1.14 netmask 0xffffff00 broadcast 192.168.1.255
media: autoselect
status: active
# wait until the dust settles. NTP takes a bit of time to get to a clean state.
electron:~ mike$ ntpq -pn
remote refid st t when poll reach delay offset jitter
==============================================================================
*192.168.1.4 .PPS1. 1 u 20 64 377 1.600 0.131 14.759
As you can see the delay and jitter (which is very variable ) go up, but the
offset stays < 1ms. So it should be possible for you to do better.
If you have another non Android wifi client on your net, what do you see with
that as a client?
>
>
> Best regards
>
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