[Linphone-users] Why Android (Oreo) phones, are actually less reliable with TCP vs. UDP

[Juha Heinanen]

Brian J. Murrell writes:

> What I am seeing is that the phone uses TCP to REGISTER to the PBX
> successfully.  If a call is made to the phone before the phone has a
> chance to go into sleep mode (i.e. right after the phone REGISTERs but
> the screen isn't turned off) everything works great.
> 
> However, once the phone does go to sleep after the screen goes off, it
> also stops responding to network packets (except seemingly Firebase
> Cloud Messaging packets on port 5228 -- which wake the phone up,
> including networking).  That means that if the PBX sends any more data
> to the phone over TCP while it is sleeping, it will go unACKed and be
> put into the TCP retry queue in the PBX's TCP stack for resend.  The
> PBX continues to retry sending the TCP packet as it is supposed to per
> the TCP protocol spec, and I believe, backing off the timeout each time
> it goes unACKed.

Brian,

I don't have that kind of problem with baresip, that uses foreground
service instead of push notifications.  The phone can go to sleep and
baresip the application can even be terminated by wiping it off and
still it answers calls over tcp or tls without issues.  Baresip's
foreground service stays alive until the phone goes to power saving mode
when the battery is about to run out.

So what you describe is Linphone's, not TCP's, fault.

-- Juha